THE FUNGI WHICH CAUSE PLANT DISEASE THE FUNGI WHICH CAUSE PLANT DISEASE BY F. L. STEVENS, Ph. D. PROFESSOR OF VEGETABLE PATHOLOGY AND DEAN, COLLEGE OF AGRICULTURE AND MECHANIC ARTS, MAYAGUEZ, PORTO RICO. FORMERLY OF THE NORTH CAROLINA COLLEGE OF AGRICULTURE ALSO FORMERLY PRESIDENT OF THE AMERICAN PHY- TOPATHOLOGICAL SOCIETY Nnn f nrk THE MACMILLAN COMPANY 1913 All rights reaerved Reprinted with the permission of Mr. Frank D. Murphy JOHNSON REPRINT CORPORATION JOHNSON REPRINT COMPANY LTD. Ill Fifth Avenue, New York, N.Y. 10003 Berkeley Square House, London, W.I COPTRIOHT, 1913 By the MACMILLAN COMPANY Set up and electrotyped. Published November, 1913 ^J-W; First reprinting, 1966, Johnson Reprint Corporation Printed in the United States of America GARDEIi TO MY WIFE ADELINE CHAPMAN STEVENS IN ACKNOWLEDGMENT OF HELP, ENCOURAGEMENT AND INSPIRATION PREFACE This volume is intended to introduce to the student the more important cryptogamic parasites affecting economic plants in the United States, with sufficient keys and descriptions to enable their identification. Technical description of each division, order, family, genus and species when important is given unless the essential characters are to be clearly inferred from preceding keys or text. Gross descriptions of the host as diseased, i, e., of the disease itself, have been avoided since such are to be found in "Diseases of Economic Plants." Effort has been made to avoid duplication of matter contained in that volume. Abundant citations to the more important papers are given, sufficient, it is believed, to put the student in touch with the literature of the subject. While many parasites not yet known in the United States are briefly mentioned, especially the more important ones or those which are likely to invade America, no attempt has been made to list all of these. Non-parasitic groups closely related to those that are parasitic have been introduced in the keys merely to give a larger perspective to the student. Effort has been made to give at least one illustration of each genus that is of importance in the United States. The author is indebted for descriptions, keys, etc., to the various standard works. Those which have been drawn upon most largely are Saccardo's Sylloge Fungorum, Die NatUrlichen Pflanzenfamilien of Engler & Prantl, Clinton's Ustilaginales of North America, Clement's Genera of Fungi, and Minnesota Mushrooms, Plowright's British Uredineae and Ustilagineae, Ar- thur and Murrill each in North American Flora. The author wishes also to express thanks for suggestions and criticism of the manuscript to T. H. Macbride, who read the por- tion on Myxomycetes; J. J. Davis, Phycomycetes; L. R. Jones vii viii PREFACE and T. J. Burrill, Bacteria; G. M. Reed, Perisporiales; G. P. Clin- ton, Ustilaginales; J. L. Siieldon, Ascomycetes in part; D. Red- dick, Ascomycetes in part; J. C. Arthur, Uredinales; F. D. Heald, Fungi Imperfecti in part; F. C. Stewart, Fungi Imperfecti in part; H. Metcalf, Basidiomycetes in part; to Mrs. Flora W. Patter- son for aid in securing descriptions otherwise unobtainable; to Dr. Marshall Avery Howe for assistance with the glossary; to Messrs. Norton, Rosenkranz and Fawcett, for aid in proof- reading and in preparation of the manuscript, though no re- sponsibiUty for error attaches to those who have so kindly aided. It is probable, owing to the present unsatisfactory condition of taxonomy of the fungi, loose and imperfect description of species, disregard of generic limitation, lack of knowledge regarding the limits of specific variation, influence of environment, biologic host relations, etc., that many of the species treated in the text are untenable. The author has, however, attempted so far as possible to reflect the facts as they appear in the light of present knowledge and has deemed it more useful to err on the side of conservatism than to attempt to reduce the apparent number of species by con- solidation without full and complete evidence as to the real identity of the species in question. F. L. Stevens. Mayagijez, Porto Rico. CONTENTS PAGE Introduction 1 Division I, Myxomycetes 5 Division II, Schizomycetes 13 Bibliography of Introduction, Myxomycetes and Schizomycetes 53 Division III, Eumycetes 59 Class Phycomycetes G5 Bibliography of Phycomycetes 103 Class Ascomycetes 113 Bibliography of Ascomycetes 288 Class Basidiomycetes 298 Bibliography of Basidiomycetes 466 Fungi Imperfecti 475 Bibliography of Fungi Imperfecti 666 Bibliography of Books and Periodicals 678 Glossary 681 Index 697 iz THE FUNGI WHICH CAUSE PLANT DISEASE INTRODUCTION The principal non-flowering vegetable parasites which cause plant diseases belong to three divisions: the Slime Molds (Myxo- mycetes) ; the Bacteria (Schizomycetes) ; and the True Fungi (Eumycetes including the Phycomycetes). The term fungi, in the broad sense, is often used to include all three of these divisions. All are devoid of chlorophyll and therefore all differ from the green plants in the essential ways which result from this deficiency. Transpiration, respiration, and true assimilation are the same as with the green plants, but photosynthesis or starch manufacture cannot be accomplished by them. Sunlight being thus useless to them directly they can live in the dark as well as the light. Having no ability to elaborate their own foods from inorganic matter these organisms are limited to such nutriment as they can obtain from plants or animals which have elaborated it; that is, they must have organic foods for their sustenance. The fungi have acquired various food habits and adapted them- selves to different methods of nutrition. Some are nearly om- nivorous and can subsist upon almost any decaying tissue or upon soils or solutions rich with organic debris. Others thrive only upon special substances, as for example, some particular plant or animal, the host, perhaps only upon some particular part of that plant or animal. The organisms tfiat prey upon living things are called parasites. Those living upon dead things are sapro- phytes. No hard and fast line can be drawn between these two classes. An organism which is usually a saprophyte may live upon a dead member of some plant, gradually encroach upon the still living part and thus become partially a parasite. Again there are times in the history of a plant when life ebbs so low that it is difficult to tell the living from the dead. The pulp of the apple 1 2 THE FUNGI WHICH CAUSE PLANT DISEASE when ripe, a resting seed, the cells of the potato tuber in winter, are undoubtedly alive, yet their activity is so little that many organisms can gain a foothold upon these stages of the plant that cannot do so at more vigorous periods of their exist- ence. Tubeuf ranks as hemi-parasites those organisms that usually are parasites, but may sometimes become saprophytic, and as hemi-saprophytes such as are usually parasitic, but may excep- tionally become saprophytic. These distinctions are of little import, other than to bring out clearly that each species has its own limits as to food requirements. It is hardly to be thought that these parasites and saprophytes have always been dependent organisms. The true fungi for ex- ample are best to be regarded as degraded descendants of algse, in which ancestors they once possessed chlorophyll and could prepare their own food from mineral matter by the aid of sun- light. No discussion of the general metabolic processes of the fungi is here necessary further than to indicate that among the products of their activity there are various excretions and secretions, which bear important relations to parasitism. Thus certain fungi grow- ing in artificial culture produce enzymes or organic ferments capable of softening and dissolving cellulose, also toxins, poisons which are capable of killing the cells of the host plant. Such enzymes and toxins are numerous and their bearing upon par- asitism is obvious. They enable the parasite to kill adjacent cells of the host and then to effect an entrance through the cell walls to the protoplasm and other nutrients contained within the cell. The presence of the parasite, or secretions produced by it, often calls forth abnormal growth responses from the host. These take very diverse forms, either the undergrowth or overgrowth, hyper- trophy, of single cells or tissues, or even the excessive development of large plant parts as in the case of the witches' brooms, and the "double flowering" of the dewberry. The probable relations of the groups under consideration to the other members of the Thallophyta are suggested in the following scheme. THE FUNGI WHICH CAUSE PLANT DISEASE ■Bacteria, Schizomycetes. ■CVANOPHYCE^, Blue-green Algae. •Myxomycetes, Slime Fungi. ■PERIDINE.E, Dinoflagellates. (Conjugate, Conjugates. DlATOME^. ■Heterocont^. ^"^■^^CHLOROPHYCEiE, Green Algae. I "<;;harace^, Stoneworts. ^^^RhodophycevE, Red Algae. ^^■^■i^EuMYCETES, Fungi. ^^■^^— "Phycomycetes* Alga-like Fungi. ^■■■^^Phjeophyce^, Brown Algae. Key to the three Divisions important as plant parasites: Vegetative body a multinucleate naked Plasmodium Division I. Myxomycetes, p. 5. Vegetative body a single-walled cell, nucleus absent or not of the form typical in the other fungi, reproduction by fission (by conidia in a few non-parasitic forms).. .Division II. Schizomycetes, p. 13. Not as above: Vegetative body usually filamentous, reproduction by various means Division III. Eumycetes, p. 59. DIVISION I MYXOMYCETES, SLIME MOLDS, SLIME FUNGI"-** (p. 3) These are the lowest organisms considered by the botanist, and partake so much of the nature of both animals and plants that their position has long been debated. Their affinities are with the lowest living things, on the boundary between the animal and the vegetable kingdom, and sometimes more attention is accorded them by the zoologist than by the botanist. The distinctive character of this group is that the vegetative condition consists either of distinct amoeboid cells or of a mass of naked protoplasm, the Plasmodium, composed of numerous cell units, each unwalled. The plasmodia, at the completion of the free vegetative stage, produce numerous walled spores either free or in sporangia of various forms. The spores upon germination produce either zoospores or amoeboid bodies which multiply and unite to form either new plasmodia or pseudoplasmodia. The slime molds consist of three orders: Key to Orders of Myxomycetes Parasitic 1. Plasmodiophorales, p. 5. Saprophytic Vegetative phase of free amoebse 2. Acrasiales Vegetative phase plasmodial 3. Myxogastrales, p. 9. The Acrasiales contain some five genera and ten species purely saprophytic. Plasmodiophorales Intracellular parasites; vegetative stage plasmodial; spores formed by the simultaneous breaking up of the Plasmodium into an indefinite number of independent cells. 5 6 THE FUNGI WHICH CAUSE PLANT DISEASE The Plasmodiophorales appear to include all of the true para- sites of the Myxomycetes. Key to Geneba of Plasmodiophorales Spores free, spherical 1. Plasmodiophora, p. 6. Spores united into groups Spores in groups of four 2. Tetramyxa, p. 8. Spores in larger groups Spores forming a hollow sphere. ... 3. Sorosphaera, p. 8. Spores forming a spongy spore-ball 4. Spongospora, p. 8. Plasmodiophora Woronin This genus is parasitic in the living parenchyma of the roots of plants, the plasmodia filling the cells and causing galls at the point of attack. There are three species of the genus in Europe and America. P. brassicse Wor.^"*' 200-203, 208 ^^^^ j^j^g ^ggj^ known as a parasite on the crucifers generally and recent work indicates that other families, as the Umbelliferae and cucurbs, are also susceptible. ^^^ The parasitised cells especially, and the adjacent cells as well, are stimulated to enormous overgrowth; this hypertrophy result- ing in a characteristic root "clubbing." Study of diseased sections shows that the medullary rays and cortex are abnormally thick (hypertrophy and hyperplasia) and many of their cells are parasitized. Sclerenchyma cells are sup- pressed by the parasite and the xylem is reduced and phloem in- creased proportionately. The amount of stored starch is much less than in normal tissues. Infection does not appear to pass from cell to cell but groups of diseased cells are thought to arise from repeated division of a cell after its infection. In the enlarged host cells the protoplasm appears abnormally dense and fine grained. Eventually the whole lumen of the cell is occupied by the crowded, amoeboid, individuals, each uninucleate and unwalled, and still distinct from the other. These individuals later fuse into a Plasmodium the nuclei of which enlarge and un- dergo simultaneous mitotic division. Still later the mass divides into uninuclear segments each of which matures to a spore 1.6 m in diameter, covered by a thin, smooth, colorless membrane. THE FUNGI WHICH CAUSE PLANT DISEASE 7 The decay of the host liberates the spores in the soil. Their germination may be readily studied upon a microscope slide where in from five to twenty-four hours uninucleate zoospores are produced. The zoospores are differentiated into an inner 10 11 Fio. 1. — P. brassicse: 3, cabbage cells occupied by the unicellular parasite; 5, later stage, parasite many-nucleate; 10, host cell full of spores; 11, germinating spores. After Lotsy. granular part and an outer hyaline part, the hyaloplasm, which may extend to form pseudopodia, thus giving the cell an amoeboid movement in addition to that due to the single long cilium. In- fection by these swarm spores is supposed to occur through the root hairs though the mode of primary infection is not definitely 8 THE FUNGI WHICH CAUSE PLANT DISEASE knovMi. Seedlings raised in soil inoculated with chopped roots bearing the disease become badly diseased as do also seedlings upon which infected water is poured. P. humili Kirk is mentioned by Kirk ^ as the cause of club root of hops in New Zealand. P. vitis Viala & Sauvageau ; ^ P. calif ornica Viala & Sauvageau ; ^ P. orchidis Massee ^° and P. tomato Abbey ^^ have been reported as the causes of serious diseases but their relation to the diseases and even their identity as actual organisms is seriously ques- tioned.12-14 Tetramyxa Goebel grows upon water plants, notably Ruppia.^ Sorosphaera Schroter (p. 6) Parasitic in the parenchyma of living plants; spores elliptic- wedge shaped, forming a hollow, spherical spore ball. One species is found upon Veronica f a second species has been reported upon tea.^'' S. graminis Schwartz is reported by Schwartz '^^ on the roots of Poa and other grasses where it caused nodules much resembling those of nematodes. Spongospora Brunchorst (p. 6) Similar to Sorosphaera but the spores forming a spore ball with open reticulations. S. subterranea (Wallr.) Lag.^^''^ causes the powdery scab of potatoes in Great Britain, Europe and South America. It has been closely studied by Osborne ^^ who shows it to appear first in the tuber cells as a uninucleate myxamceba which ultimately develops into a multinucleate amoeboid Plasmodium. Sorolpidium Nemec is a new genus with the species. S. betas Nemec which is on beets. ^^^ Several little known genera, kin to the above, attack algse, fungi, pollen, etc. Pseudomonas radicicola, the legume tubercle organism has been by some placed in this order under the name Phytomjoca legumi- nosarum. THE FUNGI WHICH CAUSE PLANT DISEASE 9 Myxogastrales (p. 5) This order comprises some forty-seven genera and four hun- dred species of great variety and beauty. The Plasmodium, which varies from a millimeter or less to several decimeters in diameter, pro- ( J nJ,/ duces either flat encrusted masses of "\ "^^^ Ih^^'^-'A spores, aethalia, or develops spores in \ _ /^ I ^ist;/ sporangia which show some superficial <^X Zi*^. resemblance to very small puffballs, Fig. 2. The interior of the sporan- gium is often permeated by a thread- ^'tu^-^^S'lX^^oSt^ like structure, the capillitium. They ^^i^. After Macbnde. are not parasites but occasionally injure plants by overgrowing them. Key to Families of Myxogastrales Spores not enclosed in a sporangium, borne externally upon the fruiting bodies. .. . 1. Ceratiomyxaceae. Spores enclosed in a sporangium Capillitium wanting, or very poorly de- veloped Periderm of uniform thickness, rup- turing irregularly 2. Liceaceae. Periderm of unequal thickness Periderm with a subapical thin line, opening by an operculum 3. Orcadellaceae. Periderm unequally thick above, the thin portions evanescent, leaving a network formed by the thicker portions 4. Cribrariaceae. Capillitium well developed Calcareous deposits absent, or rarely present in the periderm Capillitium of hollow, usually sculp- tured threads; spores light colored o. Trichiaceae. Capillitium of solid, smooth and usually much branched threads: spores dark colored Fruiting bodies aethalioid or in- 10 THE FUNGI WHICH CAUSE PLANT DISEASE definite, walls poorly defined, fraying out into a pseudo- capillitium 6. Reticulariaceae. Sporangia definite, true capilli- tium more or less prominent 7. Brefeldiaceae. Fruiting bodies separate sporangia with columella and abimdant capillitium 8. Stemonitaceae. Calcareous deposits present Capillitium not calcareous Capillitium simple 9. Didymiaceae, p. 10. Capillitium more intricate 10. Spumariaceae, p. 11. Fructification calcareous throughout 11. Physaraceae, p. 11. Didymiaceae Fructification of separate sporangia or plasmodiocarps, periderm simple or double, the outer calcareous; columella present or ab- sent; capillitial threads thin, colorless or violet, arising from the base of the sporangium or passing from the columella to the peri- derm, usually without calcareous deposits, which if present are very small crystals; spores in mass black, spore walls violet. Key to Genera of Didymiaceae Calcareous deposits in the form of stellate crys- tals, frosting the surface 1. Didymium, p. 10. Calcareous deposits not stellate. Calcareous deposits forming a superficial crust 2. Didenna. Calcareous deposits forming large superficial scales 3. Lepidoderma. Didymium Schroter Sporangia distinct, stipitate, sessile or even plasmodiocarpous, never sethalioid; the peridium thin, irregular in dehiscence, cov- ered with a more or less dense coating of calcareous crystals; columella more frequently present; capillitium of delicate threads, simple or sparingly branched, extending from the columella to the peridial wall. D. daedalium. B. & Br. is occasionally injurious to melons in culture. ^^ THE FUNGI WHICH CAUSE PLANT DISEASE 11 Spumariaceae (p. 10) Sporangia separate or sethalioid; calcarious deposit in the peri- derm or columella, never in the capillitium; capillitium radiating from various points of the columella, branching and anastomosing to form a network, the ultimate branchlets of which support the periderm. Key to Genera of Spumariaceae Fructification of ordinary sporangia 1. Diachea. Fructification sethalioid 2. Spumaria, p. 11. Spumaria Persoon Fructification a^thalioid, consisting generally of large cushion- shaped masses covered without by a white foam-like crust; within, composed of numerous tubular sporangia, developed from a com- mon hypothallus, irregularly branched, contorted and more or less confluent; the peridial wall thin, delicate, frosted with stellate lime crystals, which mark in section the boundaries of the several sporangia; capillitium of delicate threads, generally only slightly branched, terminating in the sporangial wall, marked with oc- casional swellings or thickenings. S. alba (Bui.) D. C. Like all other members of the order the present species is not a parasite but its sethalia are fre- quently produced upon grass, strawberries ^^ and other plants in such abundance as to cause more or less serious injury. The sporangia are fused into a large sethalium which is white or cream- colored, from 1 to 7 cm. long and half as thick. Physaraceae (p. 10) Key to Genera of Physaraceae Fructification sethalioid 1. Fxiligo, p. 12. Fructification plasmodiocarpous or of distinct sporangia Peridium without lime Plasmodiocarpous 2. Cienkowskia. Sporangia distinct 3. Leocarpus. Peridium calcareous, more or less throughout CapilUtium calcareous throughout 4. Badhamia. 12 THE FUNGI WHICH CAUSE PLANT DISEASE Capillitium in part hyaline Sporangium vaselike, or more or less tubu- lar Opening irregularly 5. Physarella. Opening by a lid 6. Craterium. Sporangia various, dehiscence irregular Capillitium evenly branched; the calca- reous nodes small, fusiform 7. Tilmadoche. Capillitium intricate 8. Physarum, j 12. The species of Fuligo produce very large yellowish plasmodia which change to yellowish or brownish aethalia. Some are credited with damage similar to that of the preceding species. ^^ Physarum Persoon Sporangia plasmodiocarpous, sethalioid or distinct; the peridium usually simple, sometimes double, irregularly dehiscent, more or less definitely calcareous; capillitium a uni- form irregular net, dilated and calcareous at the nodes, adherent on all sides to the peridial wall. P. cinereum (Batsch), Pers., the species most commonly reported as injurious, forms its tiny sessile, gray sporangia in great num- bers on living plants,^"' '^^ often smother- ing them. The peridium is lime charged as are also the nodes of the capillitium. The spores are brown or violet, and warty. P. bivalve F. has been noted as injuring young bean plants. ^^ Dendrophagus globosus Toumey was reported by Tourney ^^ as the probable cause of crown gall, but such relation is doubt- ful (p. 36). It is said to be closely related to Physarum. Fig. 3. — P h y s a r u m sporangium. After Macbride. DIVISION II BACTERIA, SCHIZOMYCETES"'"-^' (p, 3) Bacteria are extremely minute, unicellular organisms, which in outline present three primary forms each of great simplicity, namely the spheres (cocci), ^^ the straight rods (bacteria), the curved rods (spirilli). In addition to these forms which comprise the vast majority of known species of bacteria there are also §^o ■0' bacteria consisting of fila- Fig. 4.— The three type forms of bacteria; mentous bodies, either sim- ''• '''^''''' ^' '°^^' '• ^p^^'^'^" ^^''' ^°^°- pie or branched, attached or free. In both structure and phys- iology bacteria are allied to the vegetable kingdom and in it most closely to the blue green algse. Bacteria are inconceivably small. Most of the spherical bacteria fall within the limits of from 0.5 to 1.5/1 in diameter. Among the rod and curved bacteria the length in most species is between 1 and 1.5 n, the diameter between 0.5 and 1 n. Among the largest species is B. megatherium, 2.5 x 10 m; Clostridium butyri- cum, 3 X 10 /z; and Spirillum volutans, 13 to 50 n long. Among the smallest is Spirillum parvum 0.1-0.3 ju in diameter and Pseudo- monas indigofera 0.06 x 0.18 fi. It is practically impossible to conceive these dimensions. An illustration may aid the imagination. The paper on which these words are printed is about 87.5 m thick. It * would therefore take about 200 bacteria of ordi- FiG. 5.— This dot ia nary size or 400 moderately small or 20 very 1 mm. in diameter, j^^^.^^ ^^^^ pj^^^j ^^j ^^ ^^^^j ^^ ^q^^j -^ j^^^g^j^ the thickness of this paper. It would take 1571 ordinary bacteria (1 X 2 fi) end to end to reach around the circumference of a dot 13 14 THE FUNGI WHICH CAUSE PLANT DISEASE 1 mm. in diameter. (Fig. 5.) 500 to reach across it; and 392,700 placed side by side or 785,400 if placed on end to cover its area, and about 500,000,000 to fill a cube the edge of which is 1 miUimeter, making no allowance for lost space of the interstices. Considerably more than 500,000,000,000 bacteria of this size would find room enough to move about in a space of one cubic centimeter. The typical mode of increase among bacteria — the only mode except among the sheath bacteria — is by fission or direct divi- sion of one cell, the mother cell, into two, the daughter cells. Fig. 6. The rapidity with which fission can proceed depends of course upon conditions of environment, ranging from no growth at all, due to cold, lack of nutriment, presence of inhibiting sub- stance, to a maximum that varies with the species. For bacteria ^LA A UUIU Fig. 6. — Diagram illustrating the fission of bacteria, bacilli and cocci. After Novy. in general under very favorable surroundings, with proper tem- perature and abundance of food, from 20 to 40 minutes may be reckoned as a generation. In 24 hours, with the divisions once each hour, the progeny of one germ will be 16,777,216; with divisions each 30 minutes it will be (16,777,216)^. If cell division be in one direction only and the resulting daugh- ter cells remain undisturbed, a thread-like row results. If cell division be in two planes, and the resulting cells adhere in groups, tablets of 8, 16, and 64 will occur frequently. If the division be in three planes and their cells adhere, packets result. The structure of the bacterium cell owing to its minuteness is yet very incompletely known. The most enduring portion of the vegetative cell is the cell wall. This is surrounded by a layer, the capsule and bears the flagella. The number of the flagella and their position varies in different species. Some species have none, some one, two, or many. They may be at the ends, polar, THE FUx\GI WHICH CAUSE PLANT DISEASE 15 1. has been reported as the cause of spots on grapes under glass, also as a parasite on a large number of other plants among them Pelargonium, potato, begonia, clem- atis. It is later stated that this is probably really a variety of Ps. putrifaciens liquefaciens. B. cepivorus Del. (possibly a Bacterium) is recorded on onion bulbs.si B. coli (Esch.) Mig. or an organism indistinguishable from it is held by Johnston ^^^ capable of causing rot of soft tissues of the cocoanut plant and is perhaps responsible for cocoanut bud rot. B. cubonianus Mace, was originally described as the cause of mulberry disease (cf. Ps. mori). This organism, or at least one that was regarded as indistinguishable from it, has been men- tioned as the cause of a disease of hemp.^°^ B. cypripedii Hori is a medium sized slender, non-sporulating form with four flagella.^^^ B. delphini E. F. Sm. This is a motile, gray-white, nitrate- reducing, non-liquefying organism. On agar young colonies small, circular, wrinkled. Grows well at 30°, not at all at 37.5°. T. D. P. 48^9.1°. The cause of stomatal infection of larkspur resulting in sunken black spots on leaves and stems. ^"^ B. elegans Hegyi is reported on lupine. ^'^'^ B. dahliae Hori & Bakis is on dahlia. ^^^ B. gossypini Stedman was reported by Stedman ^°^ as the cause of cotton-boll soft rot in Alabama; much doubt, however, remains as to its actual identity and causal relation. It was de- scribed as a short, straight, spore-forming motile bacillus; 1 .5 x .75 fi; aerobic; non-liquefying (?). B. gummis Comes, has by some been held responsible for gum- mosis or mal new of the grape vine ^"^ though others discredit this idea. 44 THE FUNGI WHICH CAUSE PLANT DISEASE B. haria Hori & Miy. is a parasite of the Japanese basket willow. ^^'^ B. hyacinthi septicus Heinz/'" is recorded as the cause of a soft white rot of the hyacinth. B. lactuca? Vogl. is said to cause a lettuce disease.'^^ B. lycopersici Hegyi has been described as the cause of a rot of tomatoes.^^^ B. maculicola Del. is regarded as the cause of a tobacco leaf spot. 11^ B. melanogenus P. & M.^^'is recorded in England on potatoes. B. melonis Giddings."^ An actively motile bacillus, O.G-0.9 x 1-1.7 /z; flagella 4-6 peritrichiate; no spores. Gram negative. Broth strongly clouded, no pellicle or ring, slight sediment. Agar stroke slimy, glistening translucent; colonies round or amoeboid. In gelatine stab liquefac- tion infundibuliform in two days. Milk co- agulated with abun- dant gas. . Nitrite pro- duction abundant ; indol slight. T. D. P. 49- 50°. Opt. 30°. The vegetables rotted were muskmelon, citron, car- rot, potato, beet, cu- cumber and turnip. In the soft rot caused by this organism in muskmelons, motile bacteria were observed in abundance by Giddings in 1907. Plating gave pure cultures which by inoculation tests were shown to be those of the causal organism of the rot. Decay is produced by solution of the middle lamella by enzymic action, the remainder of the walls withstanding the attack. The bacteria are thus ip..,^ M t '"..-■ K'^ ' 1^1 m w ■' .,; V:. :-:: " v.- ■' ' ..•/ ■. ^^B^„ ■ . '■- >C^ '•^ ■ ■" *' > ■ T-? -r ': » -' H^^^^^^^^H^^t^PR Fig. 29. — Photomicrograph of B. melonis. a. show- ing living organisms in agar hanging block cul- ture; b, with flagella stained by Lowitz method. After Giddings. THE FUNGI WHICH CAUSE PLANT DISEASE 45 strictly intercellular. Wound inoculations in muskmelon generally gave complete decay in from three to seven days. Similar inocula- tion of citron and cucumbers resulted in decay, though inoculation into squash did not. No decay of musk- melon followed applications of the bacteria to unbroken surfaces. B. mycoides Fliigge. (Group number -22.1 8-.) Rods thick, 0.95 x 1.6-2.4 m, usually in long threads, sporiferous. Spores elliptical, 1.3-1.48 X 0.7-0.9 mm. Gelatine colonies white with mycelium-like outgrowths; gela- tine liquefied. Pellicle formed in broth. Gram positive. This common soil organism has been held responsible for a disease of beets. ^^^ B. nicotianae Uyeda is ascribed as the cause of a tobacco wilt in Japan ^^^' ^^^ which closely resembles that caused by B. sola- nacearum in America. The bacillus is 1-1.2 x 0.5-0.7 ^ with rounded ends, actively motile by peritri- chiate fiagella. Spores are produced. A complete physiological study is to be found in the articles above cited. Bacillus oleae (Arc.) Trev. (Group num- ber -22.333-0—.) C. O. Smith describes the organism as a motile rod with rounded ends, 1.5-2.5 x 0.5-0.6 ji. On agar slant growth thin, gray-white, spreading; colonies circular, whitish. On gelatine no liquefac- tion. Milk not coagulated. Distribution of fiagella not stated. In oleander tubercles on leaves and twigs, and in oUve tubercles C. O. Smith ^^^ found bacteria which he regards as this species. Upon puncture inocu- lation in both olive and oleander, tubercles were produced. Con- trols were not diseased. The organism was reisolated from the Fig. 30. — Cultures of B. mclonis on silicate jelly slants, 12 days' growth, (30° C.) After Gid- dings. 46 THE FUNGI WHICH CAUSE PLANT DISEASE artificially produced knot with unchanged characters. E. F. Smith's results ^° do not agree with those of C. 0. Smith. (See Pseudomonas savanastoi.) B. oleracese Harr. (Group number 221.1113022.) 120-122 This organism was studied by Harrison in 1901 in Canada where it was found associated with a soft rot of cauliflower, cabbages and turnips. In the rotting tissue it was always present; it was iso- lated, and upon inoculation and cross inoculation characteristic infection followed. The organism was reisolated in unchanged character. The chemical products of the bacillus, secured by filtration, also produced the characteristic tissue changes. Sec- tions of diseased tissue showed the bacteria in the intercellular spaces, occupying the position of the middle lamella which was softened and eventually dissolved by the bacterial enzymes. Harding and Morse ^^ from their extensive studies conclude that this form is identical with B. carotovorus. See p. 42. B. omnivorus v. Hall is described by van Hall ^"^ as the cause of a soft rot of iris shoots and rhizomes. According to Harding & Morse ^^ it does not present characters sufficient to distinguish it from B. carotovorus. See p. 42. A species closely related to B. omnivorus is described by Uyeda ^-"^ as the cause of a disease of Zingiber. The organism was isolated and studied and the disease produced by inoculation with pure culture. B. oncidii (Pegl.) Stev. is mentioned ^-^ as the cause of an orchid leaf spot. B. oryzaB Vogl. has been mentioned as the possible cause of brusone ^'^ of rice. B. phytophthorus Appel. (Group number 221.21230—.) A non-sporiferous rod, 0.6-0.8 x 1.5-2.5 n, actively motile by per- itrichiate flagella. Gram negative. It rots potatoes, cucumbers, etc.; is aerobic or a facultative anaerobe; grayish white on agar; surface colonies round, smooth; gelatine liquefaction - moderate ; bouillon clouded; no indol; no gas. Nitrate changed to nitrite. Milk coagulated and casein precipitated. Opt. 28-30°. T. D. P. 47°. It was described by Appel ^-^ of Berlin as the chief cause of potato black-leg. The description given above is by E. F. Smith ^-^ and was made from Appel's organism. Smith also isolated it from potatoes grown in Maine and in Virginia. THE FUNGI WHICH CAUSE PLANT DISEASE 47 It is closely related to but is not identical with B. solanisaprus and B. atrosepticus.^'^ B. populi Brizi is said to cause galls on the poplar ^-^. B. pseudarabinus R. G. Sm.^^" is capable of producing on inocu- lation a crimson-red gum in the vessels of sugar cane and is per- haps responsible for a disease showing this symptom. B. rosarum Scalia is the name given to a very imperfectly described organism said, on scant evidence, to be the cause of rose tumors or crown galls. ^^ B. sesami Malk.''^ Malkoff in infection experiments caused a disease of sesame with this organism. B. solanacearum E. F. Sm. (Group number 212.333-8 — .) A medium sized, easily stained, strictly aerobic bacillus with rounded ends; about 13^-3 times longer than broad; 0.5 x 1.5 /x. Motile, sluggish or active; fiagella long, diffuse. Spores not known. Zoogloea occur in liquid media as small, white flecks or as surface rings. It grows well at 20-30°. Milk is saponified with no casein precipitation or acidity. Gelatine not liquefied. Agar surface colonies, dirty-white. Agar streaks first dirty-white, later yellowish to brownish-white, then brown. On potato as on agar, but darker, with substratum and fluid browned. No gas from cane sugar, lactose, maltose or dextrose. The disease caused by this bacillus upon tomato and other plants was early studied by Halsted ^^i-iss ^^j^^ perhaps by-Bur- J.JII 134-135 Halsted made inoculations which produced the disease but he did not use pure cultures. The first complete account of the causal organism was given by E. F. Smith ^^^' ^^^ in 1896. In its hosts the bacillus is found in the pith, in the xylem which is browned, and more rarely in the bark. From the cut ends of in- fected ducts bacteria exude as a viscid ooze and the diseased ducts may be traced to great distances through the plant, even from root to leaf. From the bundles the organism later invades other tissues. Needle prick inoculations in tomatoes and potatoes with pure cultures, were followed after several weeks (tomato) by typical disease. Inoculations in Irish potato resulted similarly, though in this host the parenchyma and bark were eventually invaded, and the tuber was reached through its stem end and rotted. In South Carolina, Smith noted the disease on egg plants and crude cross 48 THE FUNGI WHICH CAUSE PLANT DISEASE inoculations were made to tomato. Smith demonstrated experi- mentally the efficiency of the potato beetle in transmitting the disease. The disease was described for tobacco by Stevens ^^^ and Stevens and Sackett.^39 Successful inoculations were reported upon tobacco by E, F. Smith in 1909 "° though in his earlier trials tobacco and pepper gave negative results when inoculated with this bacillus. In addi- tion to the above hosts it is known to grow upon Datura, Solanum nigrum, Phy sails and Petunia. B. solanicola Del. was reported as the cause of a potato stem disease.^'*^ B. solaniperda Mig. (Group number 121. — .) A rod, 2.5-4 X 0.7-0.8 n, with rounded ends, often in long chains; actively motile ; spores present. Agar colonies dirty- white ; gelatine liquefied. This was shown by Kramer in 1890 ^^^ to be the cause of soft rot of potatoes. The organism was grown in pure culture and inoculated on potatoes producing the characteris- tic decay. The germs enter through the lenticels, con- sume the sugar, then at- tack the intercellular sub- stances and the cell wall. Later the albuminous sub- stances are destroyed. B. solanisaprus Harr. (Group number 221.212-0- _ \ 143 A bacillus with rounded ends, 1.5-4 x 0.6-0.9 m, variable in culture; no capsule; actively motile by 5-15+ peritri- chiate flagella; no spores seen. Gram negative. Gelatine colonies, punctiform 0.25 mm. at two days; gelatine stab filiform. Liquefac- tion noticeable on the thirty-fifth day. Agar colonies punctiform at two days, 1-5 mm., gray-white, slimy, flat. Bouillon turbid with fine sediment; ring, and thin band present; milk curdled. Fig. 31.- -Surface colonics of B. solanisaprus. After Harrison. THE FUNGI WHICH CAUSE PLANT DISEASE 49 Gas only in mannite and lactose. Nitrate reduced to nitrite. Opt. 25-28°. T. D. P. 54°, 10 min. It was found constantly associated with a type of potato disease which Harrison regarded as distinct from black-leg and from the disease caused by B. solanacearum. It was repeatedly isolated from diseased tubers, stems and leaf veins and occurred in prac- tically pure culture in freshly infected tissue. The organisms first appeared in the ducts and thence invaded the surrounding tis- sue, dissolving the middle lamellae and producing cavities. Inoculations of pure cultures into healthy plants produced char- acteristic lesions and the organism was reisolated. Characteristic enzymic action was observed on placing precipitated enzyme on slices of potato. B. sorghi Burr."* Rods 0.5-1 (usually 0.7) x 1-3 (usually 1.5) M, cylindrical or oval, motile, spore-bearing, non-liquefying. Colonies on agar, white to pearly. In broth with a white smooth membrane. The bacillus was recognized as the cause of a sorghum blight by Burrill and this view was confirmed by Kellerman & Swingle through "^ inoculation experiments. B. spongiosus A. & R. "® causes gummosis of cherry in Ger- many. B. subtUis (Ehr.) Cohn. Straight rods, often united in threads, 0.7 x 2-8 /x. Sporiferous. Spores central or lying near one pole; germination equatorial. Flagella, 6-8, peritrichiate; gelatine liquefied; gelatine colonies Fig. 32.— B. solanisaprus, from After Harrison. agar 24 hours. 50 THE FUNGI WHICH CAUSE PLANT DISEASE bordered by numerous fine filamentous outgrowths. Growth on slant agar gray. It is reported as the cause of vegetable rot.^'*^ B. tabacivorus Del. is recorded on tobacco stems. B. tabificans Del.^^ which perhaps belongs to the genus Bac- terium is reported as the cause of a beet disease in France. B. tracheiphUus, E. F. Sm. (Group number 222. 03-.) THE FUNGI WHICH CAUSP: PLANT DISEASE 51 Bacillus 1.2-2.5 x 0.5-0.7 fx, variable, actively motile in young cultures. Capsulated, no spores, peritrichiate. No gelatine liquefaction. On agar thin, smooth, milk-white. No gas, aerobic or facultative anaerobic. Milk not curdled. T. D. P. 43°, 10 min. This pathogen was first reported by E. F. Smith without de- scription in 1893 ^^^ and more fully in 1895.^^° It is found filling the vessels of cucurbits, (musk melons and cucumbers) affected with wilt. Smith produced the disease artificially by puncture inoculations on the blades of leaves with the white sticky fluid from infected veins. The inoculated plants showed symptoms of wilt after four days and sixteen days later the ducts of the vine were found to be plugged with bacteria. The organism was then isolated from this artificially infected plant. The cultures thus obtained were carried by transfers over winter and in December were used successfully to infect cucumber plants. % , _i__„ Control plants were never * \^ ,5; ' diseased. The ready ^^ % » 1 • .-*' growth of the organism in ^ '* * ^ *^ » ^ ' * * * * ' the vessels is attributed to J Tv-.^!/ o^^i '*-••*"' V^ the alkalinity of the latter the failure to grow in the parenchyma is attributed to its acidity. ^, ,,„ v. . -"-^^ , ^ B. uvae Cug. & Mac. is T »'^**''L-c, ^* . C'V^ ^*- reported as causing injury ^j,* \^ ^^ %* ^ C*' ^^^r* to young grape clusters. ^^^ It is perhaps identical with B. ampelopsorae. B. vulgatus (Flugge) Mig. This organism is found as small thick rods with rounded ends, or is often paired or -in chains of four; sporiferous. Gelatine colonies round, liquefaction rapid. Growth on agar dirty-white. It has been shown capable of causing rot of various vegetables. ^^^ B. zeae Burr, is the name applied to a bacillus isolated from diseased corn plants by Burrill in 1887-1889.i^3' ^^^ It is often Fig. 34. — B. tracheiphilus. After Smith. 52 THE FUNGI WHICH CAUSE PLANT DISEASE cited as the cause of a bacterial corn disease but the evidence of causal relation as well as the identity of the germ are not clear. B. zinzgiberi Uyeda causes a disease of Zinzibar,-°^ B. sac- chari and B. glangae are on sugar cane as the possible cause of , 58 sereh. An organism called Clostridium persicae-tuberculosis by Cavara ^^^ is mentioned as cause of knot on peach trees. Less known bacterial plant diseases. The literature abounds in references to what are regarded as cases of plant bacteriose, cases which as yet rest upon very incomplete evidence. In many of these bacteria are found in abundance in the diseased tissue but pathogenicity has not been proved by inoculation nor pure cultures made. Among such incompletely studied diseases may be mentioned those of geranium; i^^"!^^ celery, ^^^ onion, • ^^ • ^ cucumber, ^^^ orchard grass, ^^^ lettuce, ' (one lettuce disease is due to a motile rod-shaped organism cultured and inoculated but not named, ^^'*) strawberries, ^^''"^^^ mulberry, ^^^ hemp,^^° calceo- laria. ^^^ There are also several obscure bacterial beet diseases; another cabbage rot due to Pseudomonas; ^^^ a decay of apples said by Prillieux to be due to a Bacillus; ^^^ the blossom-end-rot of tomatoes which is perhaps bacterial; ^^^ a cyclamen leaf spot; ^^^ a juniper dis- ease; ^^® a pine gall; ^^" an ash bark disease; ^^^ and an ash canker; ^^^ an ivy canker; ^^'^ a grape disease; a salsify rot; ^^^ a carnation spot; ^^^ and a banana disease; ^^^ a gummosis of tobacco; ^^* a disease of tobacco seedlings; ^^^ also perhaps the serious widespread mosaic disease of tobacco and an orchid gummosis. ^^ BIBLIOGRAPHY OF INTRODUCTION MYXOMYCETES AND BACTERIA * (pp. 1 to 53) 1 Eycleshymer, A. C, Journ. Myc. 7; 79, 1892. 2 Nawaschin, S., Flora 86: 404, 1890. » Woronin, M., Jahrb. f. wiss. Bot. 11: 548, 1878. * Rowazek, S., Arb. d. Kais. Gesund. Berlin 22: 390, 1905. » Maire, R., & Tison, A., Ann. Myc. 7: 226, 1909. <^ I(k7n., 9: 226, 1911. ' Kirk, T. W., D. Agr. R., N. Zeal., 365, 1906. « Viala & Sauvageau, C. R. 114: 1892 and 120. ^Idem., C. R., 115: 67, 1892. '0 Massee, G., Ann. Bot. 9: 95. " Abbey, Jour. Hort. Soc. London, 1895. 1= Debray, Rev. d. Viticulture, 35, 1894. " Behrens, J., Weinbau u. Weinhandel, 33, 1899. '" Ducomet, V., C. R. Ass. Fr. Avanc. Sc. Angers, Ft. 2: 697, 1903. '5 Maublanc, C., Agr. Prat. Pays Chauds. 8: 91, 1908. '•Osborne, T. G. B., Ann. Bot. 25: 271, 1911. " Lagerheim, Jour. Myc. 7: 103, 1892. i« Johnson, Sci. Proc. Roy. Dublin Soc. N. S. 12: 165, 1909. * In the bibliographies the usual abbreviations for the states followed by B. or R. indicate respectively Bulletin or Report of the State Agricultural Experiment Station, B. P. I. or V. P. P. of the Bureau of Plant Industry or Division of Vegetable Physiology and Pathology of the United States De- partment of Agriculture, respectively. Zeit.=Zeitschrift fur Pflanzenkrankheiten. Sc.«= Science New Series. E. S. R. = Experiment Station Record. Ann. Myc.=Annales Mycologici. Soc. M. Fr.=Societe Mycologique de France. Y. B. = Yearbook, U. S. Department of Agriculture. C. R. = Compt. Rendu. C. Bak. = Centralblatt f. Bakt. Par. u. Inf. Ab. II. Other abbreviations are those usually employed or readily understood. All bold face references,®**** will be found in the book bibliography, page 678 53 54 THE FUNGI WHICH CAUSE PLANT DISEASE » Johnson, Econ. Proc. Roy. Dublin Soc. 1, pt. 12, 1908. 2» Wulff, T., Zeit. 16: 203, 1906. " Mangin, L., Rev. Hort. Paris 81: 568. « Zeit. 13: 267, 1903. " Tourney, Ariz. B. S3. 2" Prillieux, E., Ann. Sc. Nat. 6 ser. 7: 248, 1879. " Frank, Ber. d. Deut. Bot. Gas. 16: 237, 1898. 28 Frank, C. Bak. 5: 98, 1899. " Roze, E., C. R. 122: 543, 1896 and 123: 1323. 28 Delacroix, G., Maladies d. PI. Cult. 19, 1909. " Metcalf, H., Neb. R. 17: 69, 19(M. '« VuiUamen, C. R. 107: 874, 1888. " Busse, W. & V. Faber, F. C, Mit. K. Biol. Anst Land u Forst, 18, 1907. '2 Jones, L. R., N. Y. (Geneva) T. B. 11: 1909. " Harding, H. A., and Morse, W. J., N. Y. (Geneva) T. B. 11: 1909. "^ Smith, E. F., V. P. P. 28: 1901. " Manns, T. F., 0. B. 210: 1909. 36 Pammel, L. H., la. B. 27: 1895. " Russell, H. L., Wis. B. 65: 1898. 58 Smith, E. F., B. P. L 29: 1903. '9 Smith, E. F., C. Bak. 3: 284, 485, 1897. « Harding, H. A., Stewart, ¥. C., and Prucha, M. S., N. Y. (Geneva) B. 251: 1904. " Garman, H., Ky. R. 5; 43, 1890. ^2 Harding, H. A., C. Bak. 6: 305, 1900. '' Potter, M. C., C. Bak. 7: 282, 1901. '' Jones, L. R., C. Bak. U: 257, 1905. *' Arthur, J. C. & BoUey, H. L., Ind. B. 59: 17, 1896. « Barlow, B. B., Ont. Ag. Co. B. 136: 1904. « Griffon, E., C. R. Acad. Sci. Paris 149: 50, 1909. ^8 Scalia, Agricolt Calabro-Siculo, 1903. « Smith, E. F., V. P. P. 26: 1901. ^« van Hall, C. J. J., Zeit. 13: 129, 1903. " Pierce, N. B., Bot. Gaz. 31: 272, 1901. ^2 von Oven, E., C. Bak. 16: 1907. " Osterwalder, A., Cent. Bak. 25: 260, 1910. '* Sackett, W. G., Colo. B. 158: 1910. " Smith, E. F., Sc. 31: 794, 1910. 6" Boyer & Lambert, C. R., Paris 117: 342, 1893. " Smith, E. F., Sc. N. S. 31: 792, 1910. BIBLIOGRAPHY OF INTRODUCTION 55 '8 Macchiati, L., Malpighia 5: 289, 1892. s» Beach, S. A., N. Y. (Geneva) B. 48: 331, 1892. «" Halsted, B. D., N. J. R. 13: 283, 1892. 81 Smith, E. F., Proc. A. A. A. S. 288: 1897. «2 Smith, E. F., Sc. 17: 456, 1903. " Rorer, J. B., MycoHgia 1: 23, 1909. " Pierce, G. P., Proc. Cal. Acad. Sc. 3rd Ser. Bot. 2: 295, 1902. 85 Smith, E. F., B. P. I. 131: 25, 1908. 86 Malkoff, K., C. Bak. 16: 664, 1906. 8^ Stewart, F. C., N. Y. (Geneva) B. 130: and R. lU: 401, 1897. 88 Smith, E. F., Proc. A. A. A. S. 422: 1898. 85 Smith, E. F., C. Bak. 10: 745, 1903. ™ Smith, E. F., Sc. 17: 458, 1903. 71 van Hall, C. J. J., Bij. t. Kenn. Bak. Plonet 142, 1902. " Smith, E. F., and Towiisend, C. 0., Sc. 25: 672, 1907. " C. Bak. 20: 89. '" Townsend, C. 0., Sc. 29: 273, 1909. " Smith, E. F., Phytopathology 1: 7, 1911. '« Smith, E. F., Brown, N. A., and Townsend, C. O., B. P. I. 213, 1911. " Cobb, N. A., New So. Wales, Dept. Agr. 1893. ™ Smith, E. F., C. Bak. 13: 726, 1905. " Brown, Nellie A., Sc. 29: 914, 1909. 80 Jamiesson, Clara 0., Sc. 29: 915, 1909. 8' Delacroix, G., Ann. Inst. Nat. Agron. 2, Ser. 5: 353, 1906. 8= Burrill, T. J., Trans. 111. Hort. Soc. 114, 1877. 8» Idem, 80, 1878. 8" Burrill, T. J., Proc. A. A. A. S. 29: 583 and Am. Nat. 15: 527. 85 Arthur, J. C, N. Y. (Geneva) R. 3: 1884. 88 Arthur, J. C, Proc. A. A. A. S. 31,: 1885. 87 Arthur, J. C, Bot. Gaz. 10: 343, 1885. 88 Arthur, J. C, Proc. Phila. Acad. Science 331, 1886. 89 Jones, L. R., C. Bak. 9: 835, 1902. 9° Paddock, W., Col. B. 84. 91 Detmers, F., 0. B. Ser., IV: No. 6, 129, 1891. 9= Whetzel, H. H., N. Y. (Cornell) B. 236, 1906. 93 Burrill, T. J., Trans. 111. Hort. Soc. 147, 1881. 9^ Brizi, U., C. Bak. 3: 575, 1897. 95 Halsted, B. D., N. J. B. Q: 1892. 98 Rankin, W. H., Special Crops. N. S. 9: 94, 356. " Uyeda, Y., see 96. 98 Townsend, C. 0., B. P. I. 60: 1904. 56 THE FUNGI WHICH CAUSE PLANT DISEASE 93 van Hall, C. J. J., Diss. 1902. "0 Busse, W., Zeit. 7: 65, 1897. 101 Delacroix, C. R. llfi: 1356, 1905. lo^ Jones, L. R., C. Bak. 7; 12, 1901. 10' Jones, L. R., Vt. R. IS: 299, 1901. 10* Harding & Stewart, Sc. 16: 314, 1902. 10* PegUon, v., Zeit. 7: 81. io« Smith, E. F., Sc. 19: 416, 1904. 107 Hegyi, Kizer Kozlem 1: 232, 1899. 108 Stedman, J. M., Ala. B. 55: 1894. 109 Prillieux & Delacroix, Rev. Int. d. Vit. D'Oenol, 1894. 110 Heinz, Cent. f. Bakt. 5: 535, 1889. 111 Voglino, P., An. R. Ac. d. Agr. d. Torino 4^.- 1903. 1" Hegyi, D., Riser. Kozlem 2: 1899, No. 5235. 11' C. R. IhO: 678, 1905. 11* Pethybridge, & Murphy, P. A., Nature (London, 1910), 296, No. 2148. 11* Giddings, N. J., Vt. B. IJ^S: 1910. ii« Linhart I., Zeit. 10: 116, 1900. 1" Uyeda, Y., Bull. Imp. Centr. Agric. Sta. 1: 39, Dec, 1905. '18 Uyeda, Y., C. Bak. IS: 327, 1904. 1" Smith, C. O., Bot. Gaz. 1^.2: 302, 1906. 120 Harrison, F. C, C. Bak. IS: 46, 1904. 121 Harrison, F. C, Sc. 16: 152, 1902. 1" Harrison, F. C, Ont. B. 1S7: 1904. 1" van Hall, C. J. J. Zeit. IS: 129, 1903. 1" Uyeda, Y., Bot. Cent. 17: 383, 1907. 1" Voglino, P., Bot. Cent. 274, 1893. 128 C. Bak. 5: 33, 1899. 1" Appel, 0. Arb. aus. Biol. Abt. Kaisel Gesundtheilamt 3: 364, 1903. 128 Smith, E. F., Sc. SI: 748, 1910. 129 Brizi, U., Atte. Cong. Nat. Ital. Milan, 1907. "0 Smith, R. G., Proc. Lin. Soc. N. S. Wales 29: 449. "1 Halsted, B. D., N. J. R. 12. "2 Halsted, B. D., N. J. R. I^: 267, 1891. 1" Halsted, B. D., Miss. B. 19: 1892. 134 Burrill, T. J., Proc. 11th Ann. Meeting Soc. Prom. Agr. Sci. 21, 1890. "* Ibid. 29, 1891. "0 Smith, E. F., V. P. P. 12: 109, 1896. 1" Smith, E. F., Proc. A. A. A. S. 191, 1895. 138 Stevens, F. L., Press Bull. N. C. 11: Aug. 1903. BIBLIOGRAPHY OF INTRODUCTION 57 "9 Stevens, F. L. and Sackctt, W. G., N. C. B. 188: 1903. '"o Smith, E. F., B. P. I. 141, Pt. II, 1909. '" Delacroix, G., C. R. 133: 417, 1030, 1901. »« Kramer, E., Oest. land. Cent. 1: 11, 1891. '" Harrison, C. Bak. 17: 34, 1907. '" Burrill, T. J., Proc. Am. See. Mic. 1888. i« Kellerman, W. A. and Swingle, Kan. R. 1: 1888. ^^« Aderhold and Ruhland, Arb. d. Kais. Biol. Anst f . Land. u. Forst. 5: 1907. 1" van Hall, C. J. J. C. Bak. 9: 642. i« Delacroix, C. R. 37: 871, 1903. i« Smith, E. F., Bot. Gaz. IS: 339, 1893. ""Smith, E. F., C. Bak. 1: 3G4, 1895. "' Macchiati, L., Rev. inter d. Vit. et D'Oenol. 1: 129, 1894. 1" van Hall, C. J. J. C. Bak. 9: 642, 1902. 153 Burrill, T. J., Billings, the com stalk disease in cattle investigation 3: 163, 1889. 1" BurriU, T. J., 111. B. 6: 1889. 1" Sta. Sperim Agr. Itat. 30: 482, 1897, also Zeit. 8: 37. "« Stone, G. E., and Smith, R. E., R. Mass. (Hatch) 12: 57, 1900. '" Stone, G. E., and Monahan, N. F., R. Mass. Sta. 19: 164, 1907. i=-8 Galloway, B. T., J. Myc. 6: 114. 1'^ Stewart, F. C., N. Y. (Geneva) B. 164, 1889. ""Halsted, B. D., N. J. R. 11: 1890. "' Stone, G. E., and Monahan, N. F., R. Mass. Sta. 19: 161, 1907. •«2 Rathay, E., Sitz, K. A. K. Wiss. Wien 597, 1899. "3 Jones, L. R., Vt. R. 6: 1892. '" Fawcett, H. S., Fla. R. 1908, 80. "5 Detmers, 0., B. 4: 1891. 166 Voligno, P., Zeit. 11: 150. '" Stone & Smith, Mass. R. 1896. '^8 Smith, R. E., Mass. R. 9: 59, 1897. 1" Cavara, Sta. Spm. Agr. ital. 30: 482, 1897. ""Peglion, Zeit. 7." 81, 1897. '7' Halsted, B. D., N. J. R. 430, 1893. 1" Spieckermann, Land. Jalir. 31: 155, 1902. 1" Prillieux, B. Soc. Bot. d. France 33: 600, 1896. ''•• Earle, F. S., Ala. B. 108: 19, 1896. "* Prillieux, E. & Delacroix, G., C. R. 118: 668, 1894. "•Cavara, B. Soc. Bot. Ital. 241, 1898. i"Tubeuf, Nat. Zeit. Forst und Land. 9: 25, 1911. 58 THE FUNGI WHICH CAUSE PLANT DISEASE "8 Jour. Bd. Agr. London, 17: 478. 1" Noack, F., Zeit. 3: 191, 1893. 18" Lindau, Zeit. J^: 1, 1894. 181 Halsted, B. D., N. J. R. 11: 351, 1890. 182 Woods, A. F., Sc. iS; 537, 1903. 183 Rorer, J. B., Proc. Agr. Soc. Trinidad and Tobago, 10: No. 4. 18^ Honing, J. A., Med. Deli. Medan 5: 24. 185 Comes, 0. Atti. d. R. Inst. d'Incor. d. Napolo, 4- 6, 1893. 186 Potter, Gard. Chron. Mch. 6, 145, 1909. 18' Schwartz, E. J., Ann. Bot. 25: 791, 1911. 188 Nemec B., Ber. d. deut. Bot. Gez. 29: 48, 1911. 189 Johnston, J. R., Phytop. /.• 97, 1911. "oPavarino, G. L., Atti R. Acad. Lincei CI. Sci. Fis. Mat. e. Nat. 6: 355, 1911. 1" Boyer & Lambert, C. R. 128: 342, 1893. 192 Pavarino, L., Riv. d. Pat. Veg. 5: 65, 1911. 1" Halsted, B. D., N. J. B. Q., also R. 1891, 558. 19* Cavara, B. Soc. Bot. Ital. 241, 1898. 195 Stevens, F. L., N. C. R. 31: 74, 1908. i96Hori, S., C. Bak. 31: 85, 1911. i97Hori, S., B. Imp. Cent. Ag. Ex. Sta. Nishigahara, 1910. ^^^Idem., 11, 1911. 199 Marchand, E. F. L., C. R., heb. d. seans. d. I'ac. d. Sc. 150: 1348. 200 Stewart, F. C, N. Y. (Geneva) R. U: 525, 1895. 201 Kirk, N. Zeal. R. 13: 427. 202 Jones, L. R., Vt. B. 66: 1898. 203 Halsted, B. D., N. J. R. 306, 1896. 204 McCuUoch, L., B. P. I. 225: 1911. 205 Orton, W. A., Farm B. U: 309, 1907. 206 Uyeda, Y., C. Bak. 17: 383, see also extensive Japanese publica- tion later by Uyeda. zo^Sackett W. G., Col. B. 177: 1911. 208 Bull. No. 2, 1896, p. 76, Torr. Bot. CI. 209 Jour. Am. Pub. H. Assn., Jan. 1898: 60; Recommendation for the study of Bacteria. See also Rept. Soc. Am. Bact. Meeting of 1907. 210 Pavarino, L., Rend. d. r. Ac. d. Lincei, Classe Scienze, 20: 161, 1911. DIVISION III EUMYCETES. TRUE FUNGI (p. 3) '"• ''■ ''■ ''■ "' "■*' The Vegetative Body is devoid of chlorophyll and typically consists of a more or less branched filament of apical growth, the mycelium. This mycelium may be cut into cells by partitions (septa) or may be continuous, i. e., without septa. The cells of the septate mycelium do not differ essentially from typical plant cells except in the absence of chlorophyll. They consist of masses of protoplasm, the protoplasts, bearing vacuoles and are more or less rich in oils, acids, ^ gums, alkaloids, sug- ars, resins, coloring matter, etc., varying in amount and kind with the particular species and condition of the fungus. The protoplast is covered by a cell wall which consists of cellulose though often of a special quality known as fungous cellulose. The protoplast bears one or in some fungi two or more nuclei. The vacuolation of the protoplasm, the mode of branching of the cells, their color, dimensions, etc., are in some cases quite charac- teristic. In one class, the Phycomycetes, the active vegetative mycelium possesses no septa except such as serve to cut off the sexual or other reproductive organs or such as are found in senility. The 59 Fig. 35.- -Showing a septate mycelium within host cells. After Stevens and Hall. 60 THE FUNGI WHICH CAUSE PLANT DISEASE protoplasm is therefore continuous throughout the whole plant body and may be regarded as constituting one cell though it may be of great extent and bear very numerous nuclei. Such multi- nucleate cells, coenocytes, may be regarded as cell complexes with the walls omitted. In one comparatively small order, the Chytridiales, there is often no filamentous mycelium and the vegetative body consists merely of a globular, irregularly spherical or amoeboid cell. Such forms are thought by some mycologists to be degenerate, to have in remote time possessed a mycelium which has been lost owing to the present simple mode of life of the fungus, the needs of which no longer call for a filamentous body, while others ^ find here primitive forms of Phycomycetes, and trace their phylogenetic connection with the higher orders of the class. Reproduction. Vegetative. Most mycelia, if cut in bits and placed in suitable environment, continue to grow, soon equaling the parent mycelium in size if abundant nourishment obtains. Bits of diseased tissue, bearing mycelium, thus con- stitute ready means of multiplication and dis- persal. Asexual Spores. A spore is a special cell set aside to reproduce the plant. An asexual spore is a spore not produced by a sexual process. Manifold forms of asexual spores exist among the fungi. In some of the simplest cases, bud- like out-growths (gemmae) appear on the myce- lium; or portions of the mycelium itself are cut off by partitions and the protoplasm inside gathers into a mass and protects itself by a firmer wall than that of the mycelium, chla- mydospores. In other cases special branches, Fig. 36.— One form hyphae, are set apart for the purpose of bearing of conidium. t/- ji j. £p r j.t- j.* r Oidium. After spores. If the spores are cut on from the tip of Bioiotti. ^Yie branch they are known as conidia or conidio- spores, and the branch bearing them is a conidiophore. Conidia may be borne singly or in false clusters caused by the youngest pushing the older conidia aside; frequently they are produced in THE FUNGI WHICH CAUSE PLANT DISEASE 61 chains, catenulate, Fig. 36, owing to the development of one spore below another before the elder spore is shed. Conidia may be either simple, composed of one cell, or compound, composed of two or more cells. In compound spores each cell is at least potentially a spore and can germinate under favorable conditions and per- petuate the species. In many compound spores the germinating function is sacrificed by one or more of their component cells. Conidiophores may consist of loosely branching, rather long hyphae, or they may be short, innate, and in close clusters forming distinct spore bearing spots. Fig. 371. Such sporiferous spots when naked are called acer- vuli. Often the conid- iophores are roofed over with a net-work of woven fungous threads thus constituting a special spore-bearing structure, the pycnidium. Figs. 37, 335. Conidio- phores may be solitary or grow together in bun- dles or branch loosely as in Fig. 383. The basidium, Fig. 38, is a special kind of sporo- phore bearing at its Fig. 37.— Conidia borne in a pycnidium. „„„„ ,,„ n r Quaintance and Shear. apex usually tour, or two, small projections, sterigmata, each of w^hich produces one spore, for distinction called a basidiospore. Some fungi bear the spores loose inside of the swollen tips of sporophores as in Fig. 68. The spore bearing structure is then called a sporangium and its stalk a sporangiophore. The ascus is another spore bearing structure. In it the spores are borne very much as they are in the sporangium but usually of definite num- ber, 1, 2, 4, 8, 16, etc., eight being the most common number. Asci may be naked or covered, scattered or collected in groups. After 62 THE FUNGI WHICH CAUSE PLANT DISEASE When covered, the chamber in which they are borne is called a perithecium, Fig. 39; when on an open disk the disk is called an apothecium, Fig. 101. According to their length of life spores are classed as: 1. rest- ing spores whose function is to tide over unfavorable conditions, hence the common name "winter spore," and in contradistinction: 2. "Summer spores" which are produced in abun- dance in warm weather, germinate immediately, and can ordinarily live but a short time. In some species the spores that are to func- tion in water possess cilia, and the power of motion. These are zoospores or swarm spores, Fig. 44. At sporing time many kinds of fungi produce special structures for the bearing of spores. The fungous threads interweave to form a firm, or even a densely solid, mass and constitute a false parenchyma. Such are the stalks and caps of the mushrooms and of the shelving toadstools, the skin of the puff ball, etc. A cross section of such a structure appears much as a true parenchyma, a longitudinal section shows it to be merely a mass of interwoven fungous threads. Sexual Spores are formed by the union of sexual elements, gametes. They are most conspicuous among the Oomycetes where the antheridium carries the sperms into the oogonium, fertilizes the obsphere and produces an oospore. Figs. 53-55. As a rule the sexual spores are produced toward the end of the vegetative period of the fungus. The asexual spores are produced earlier and for a longer period. Sexual spores are commonly resting spores. Germination of spores. Under suitable environment mature spores germinate and eventually give rise to vegetative bodies r-sk Fig. 38. — Basidia of various ages. After Schenck. THE FUNGI WHICH CAUSE PLANT DISEASE 63 similar to that of the parent. The most usual mode is for the mycelium to rise directly from the spore. In other instances the spores produce zoospores which migrate, come to rest, then develop a mycelium. In still other cases a short mycelium, promycelium, is formed and from this small conidia, sporidia, are made. Figs. 217, 240. These conidia give direct rise to the mycelium. Spores of some species may by gemmation lead a more or less prolonged existence without return to the mycelial stage. Heat and Moisture Relation. Like all living things these organisms cannot develop without heat and moisture. The necessary degree of each varies with different species. Some qermimr/on Fig. 39. — A perithecium with asci. After Reddick. species are strictly aquatic, and must be surrounded with water; others can grow in comparatively dry situations. Generally speaking, however, dampness favors fungous development, and the growth of most fungi is more vigorous in a damp atmosphere than in a drier one. Similarly moderate warmth, as that of summer heat, favors fungous growth. Humidity and warmth combined are proverbial as producers of mold and mildew. So conspicuous is the coincidence of these conditions with fungous growth, that in the minds of many a warm damp air is the cause rather than the condition of fungous development. Respiration with the fungi as with other plants and animals consists in oxidation, involving intake and consumption of oxygen accompanied by the giving off of carbon dioxide antl water, and 64 THE FUNGI WHICH CAUSE PLANT DISEASE since no photosynthesis occurs, this process is never masked as it is in the case of the chlorophyll-bearing plants. In nutrition requirements there is great diversity; but in all cases carbon must be taken from some organic source. Starch, sugar, cellulose and kindred compounds are frequent sources of the carbon food supply. Nitrogenous foods are, generally speaking, not required in such abundance by the Eumycetes as by the bacteria and advantage may frequently be taken of this fact in isolating the fungi from bacteria by growing them on media poor in nitrogen, in which case the fungi often outgrow the bacteria. The color of the fungi is determined largely by the constitution of the media upon which they grow.^* ^' ■*' ^ Many fungi exhibit a peculiar heteroecism, that is, part of their life cycle is passed through upon one host, part of it upon another host, even of very distant botanical kinship. Thus among the rusts; in one instance part of the life cycle is upon the apple, the remainder upon the cedar tree. Fungi also exhibit polymor- phism, i. e., in one stage they exhibit one spore form and in an- other stage another spore form totally different. In this way several apparently quite distinct types of spores and sporiferous structures may belong to the same species. Classification of Fungi.®' '^' ^^' ^^' ^''' ^^ The true fungi in them- selves constitute a very large group made up of diverse forms, many of which are as yet little known. Any satisfactory system of classi- fication is impossible until much more knowledge is gotten regard- ing their morphology, cytology, life histories and especially their re- lations to their hosts. According to present knowledge they com- prise very numerous species distributed in three classes as follows: Key to Classes of Eumycetes Mycelium continuous in vegetative stage Class 1. Phycomycetes, p. 65. Mycelium septate Spores in asci Class 2. Ascomycetes, p. 113. Spores on basidia* Class 3. Basidiomycetes, p. 298. Not as above; spores on conidio- phores, naked, or in pycnidia; or spores quite unknown Fungi Imperfecti, p. 475. * In the rusts and smuts the promycehum is regarded as a basidium. THE FUNGI WHICH CAUSE PLANT DISEASE 65 Class I. Phycomycetes, Alga-like Fungi (p. 64) The Phycomycetes are characterized by the absence of septa in the mycelium except in sporing branches, where they occur to cut off the spore-bearing cells or the gametangia, and in old fila- ments. The body is multi-nucleate and sexual spores as well as asexual ones are usually, though not always, produced. Some of the Phycomycetes live in water and possess zoospores, others are parasitic on land plants and bear conidia or sporangia. These may germinate either by germ tubes or by zoospores. The char- acteristic fertilization consists of a union of two gametes which may be like in character (isogamy) or unlike (heterogamy). If the sexual organs are unlike the receptacle which bears the sexual spores is called the oogonium, its eggs before fertilization oospheres, and the spores oospores. The receptacle bearing the fertiliz- ing gamete is the antheridium, and the fertilizing elements are the sperms. The sperms may be motile and swim or creep into the oogonium or the antheridium may develop a tube leading into the oogonium through which the fertilizing nuclei pass. In some forms which, by their sexual or asexual spores, show relation to the Phycomycetes the mycelium is wanting and the vegetative body is reduced to a single spherical or amoeboid cell, which fre- quently lives in a purely parasitic manner entirely imbedded in the protoplasts of its host. This mode of life constitutes the strictest kind of parasitism inasmuch as the fungus derives its nourishment from the still living host cell. Key to Orders of Phycomycetes Sexual spores when present heteroga- mous Subclass I. Obmycetes, p. 66. Conidia absent; sexual spores and zoo- sporangia only Mycelium poorly developed, frequently reduced to a single cell Fruiting mycelium a single cell, or a group of cells in a sorus, forming either asexual resting spores or sporangia from the entire proto- plasmic mass 1. Chytridiales, p. 66. 66 THE FUNGI WHICH CAUSE PLANT DISEASE Fruiting mycelium multicellular, some cells forming sporangia, others producing gametes and oospores 2. Ancylistidiales. Mycelium well developed Fertilization by motile sperms. ... 3. Monoblepharidiales. Fertilization through an anther- idial tube 4. Saprolegniales, p. 74. Conidia present 5. Peronosporales, p. 77. Sexual spores isogamous, formed by the union of similar gametes.. Subclass II. Zygomycetes, p. 101. Asexual spores several, in sporangia. . . 6. Mucorales, p. 102. Asexual spores sohtary, conidia 7. Entomophthorales, p. 107. Of these orders the Ancylistidiales which are parasitic upon Algse, and the Monoblepharidiales which are saprophytic will not be considered further. Subclass Oomycetes (p. 65) In the Oomycetes there is pronounced difference between the male and female sexual organs. The oogonium is comparatively large, and contains one or more large passive eggs (oospheres), which are fertilized by sperms, differentiated or not, which either swim to the oogonium by cilia, creep to it, or are carried to it by a fertilizing tube. Oospores are in some species produced fre- quently and abundantly while in others they are entirely unknown. The asexual reproduction is by either conidia or sporangia. Chytridiales (p. 65) The members of this order are the simplest of any of the Phy- comycetes. Many of them are single, more or less globose, undif- ferentiated cells, others have a more or less prominent haustoria- like mycelium, while but few have any approach to a true myce- lial development. Most are intracellular parasites; a few of the more highly developed genera are intercellular parasites. With few exceptions reproduction is entirely asexual, all spores being formed directly from the vegetative cell. Zoosporangia and thick- THE FUNGI WHICH CAUSE PLANT DISEASE 67 walled resting spores are produced. The zoospores have cither one or two cilia. There are over forty genera and two hundred species. The majority of the species are inconspicuous parasites of algse and infusoria; but some genera, like Synchytrium and Urophlyctis, produce conspicuous sori and even cause hyper- trophy of land plants. Key to Families of Chytridiales Spores all asexual, or rarely formed by the union of free-swimming gametes Mycelium none Sporangia solitary 1. Olpidiaceae, p. 67. Sporangia grouped into sori 2. Synchytriaceae, p. 69. Mycelium present Mycelium of delicate, evanescent haus- toria-like strands Mycelium limited, sporangia ter- minal 3. Rhizidiaceae. Mycelium extended, sporangia ter- minal or intercalary 4. Cladochytriaceae, p. 72. Mycelium of permanent hyphse 5. Hypochytriaceae. Spores both sexual and ase.xual Gametes hetrogamous G. Oochytriaceae, p. 73. Gametes isogamous 7. Zygochytriaceae. Four only of these families have parasitic representatives on higher plants in America, the others being chiefly parasitic on algae and infusoria. Olpidiaceae This family which contains the simplest members of the order has no mycelium; the entire plant body consists of a single more or less globular or elliptic cell which never divides, but at maturity forms either a zoosporangium or an asexual resting spore which after a period of rest gives rise to swarm spores. All the species are endobiotic. The family contains some forty species but few of which are of economic importance. 68 THE FUNGI WHICH CAUSE PLANT DISEASE Key to Geneea of Olpidiaceae Vegetative body amoeboid Vegetative body of definite form Sporangia free in the cells of the host Sporangial membrane very delicate, evanescent Sporangial membrane firm, swarm spores escaping by a definite open- ing Sporangium globular or ellipsoid Sporangium with only one or two openings Swarm spores uniciliate Vegetative cells globose or sub- globose Vegetative cells stellate Swarm spores biciliate Sporangium ^^^th several openings Sporangium elongate Sporangial membrane united to the wall of the host cell 1. Reessia. 2. Sphaerita. 3. Olpidium, p. 68. 4. Asterocystis, p. 69. 5. Olpidiopsis. 6. Pleotrachelus. 7. Ectrogella. 8. Pleolpidium. Olpidium A Braun In this genus a single swarm spore invades the cell of the host and develops in its pro- toplasm. Later a cell wall forms and the vege- tative body changes into a zoosporangium which develops a neck. This reaches to the outside of the host even though the fungus be developed several cells below the surface. The uniciliate Fig. 40.— O. brassier; right, three sporangia in ZOOSporeS paSS OUt a cell; left, resting spores. After Woronin. through this neck tO make their escape. Thick-walled resting spores are also formed. THE FUNGI WHICH CAUSE PLANT DISEASE 69 There are some twenty-five species most of which hvc as para- sites on algse, worms, pollen grains, etc. O. brassicae (Wor.) Dang.^ is parasitic on quite young cabbage seedlings, sometimes infecting cells deeply seated in the host. The same or a nearly related species also attacks tobacco and several weeds. Sporangia solitary or several in each infected host cell, globular; zoospores numerous, globose, uniciliate; resting spores globose, with a wrinkled epispore which gives them more or less of a star- like appearance. Fig. 40. Asterocystis de Wildeman (p. 68) There is a single species, A. radicis d. Wild.^ which differs from Olpidium in its stellate vegetative cell and the absence of the tube for the escape of the zoospores, this being accomplished by the breaking away of the tissues of the host. The fungus attacks the roots of various plants, notably flax, Brassica and other crucifers, Plantago, Veronica and numerous grasses, producing chlorosis. It has not been reported from America. A Chytridiaceous fungus of unknown genus thought to stand near the Olpidiaceae and Synchytriaceae has been described by Home ^ as the cause of an Irish potato disease. Synchytriaceae (p. 67) The infecting zoospore invades the host cell and becomes parasitic upon the still living protoplasm. Hypertrophy of this and adjacent host cells is usually induced, resulting in the formation of a small gall around the infected cell. This gall is often colored and bears a superficial resemblance to a rust sorus. The parasite enlarges until it occupies nearly the whole of the host cell. In S>Tichytrium the one nucleus then enlarges and divides to produce very numerous nuclei. ^' ^"' ^^' ^" The whole mass then divides into segments regarded as sporangia, and each sporangium divides into numerous uninucleate parts, each of which develops into a zoospore. In some species development is arrested before the division of the primary nucleus and the protoplast becomes spherical, invests itself with a thick wall and becomes a resting 70 THE FUNGI WHICH CAUSE PLANT DISEASE spore. (Fig. 42.) After a more or less protracted period of rest this produces zoospores. The family includes some fifty species, all of which, except two small genera, are parasitic upon land plants. Key to Genera of Synchytriaceae Zoosporangia formed by direct division of the entire plasma of the young fruiting body. Swarm sporangia completely filling the host cell, membrane united to the wall of the host cell 1. Rozella. Swarm sporangia lying free in the host cell Parasitic on algse 2. Woronina. Parasitic on land plants 3. Woroniella. Zoosporangia formed by division of an ini- tial cell to form a sorus of sporangial cells. Sporangia formed directly, from the full- grown plant body 4. Synchytrium, p. 70. Sporangia formed by the division of a thin- walled mother cell after its escape from the plant body 5. Pycnochytrium, p. 72. Synchytrium de Bary & Woronin Upon reaching maturity the plant body develops directly into a sporangial sorus. Both zoosporangia and winter spores present. Fig. 41. — Showing nucleus in bynchytrium. After Stevens. S. endobioticum (Schilb.) Perc, the cause of a very serious wart disease of the potato, was originally described as Chrysophlyctis endobioticum by Schilberszky ^^ and transferred to Synchytrium by Percival.^^ It invaded America about 1909.^^^ It was reported from Africa by Zimmermann.^^ THE FUNGI WHICH CAUSE PLANT DISEASE 71 Fig. 42. — A, section showing sporangia or sporocysts; B, zo6si)ores, ciliated and amoeboid. After Percival. In summer the resting spores which average about 52 n in diam- eter are found in abundance in the host cells near the surface, few in the outer layer, more below down to the sixth or eighth row of cells. Each resting spore contains several hun- dred roundish zoospores which measure 2-2.5 /x. In spring the resting spores germinate, freeing numerous pear-shaped uniciliate zoospores, which at first swim with a jerky motion but soon become amoeboid. The summer sporangia may germinate without protracted rest, and also give rise to zoospores. Another type of sporangium consists of thin sacs, produced singly or two to five in a sorus, each bearing numerous zoospores somewhat smaller than those from the first type of sporangia. The zoospores, says Percival, enter the potato apparently in the amoeboid state in bud tissue of rhizomes and in the "eyes" of young tubers. Usually only one zoospore enters each cell but occasionally more may do so. Crushed sporangia produced characteristic warts in three to four days when placed on suscep- tible parts. Successful inoculations were also made by Salmon and Crompton.^^ The cytology has been studied by Percival. ^^ The full grown tumors vary in size from that of a pea to a hen's egg, and represent metamor- phosed branch systems. S. vaccinii Thomas ^^"^^ is the cause of a disease of the cranberry and related hosts. It forms numerous, small, reddish galls in which, deeply embedded, are the sori. S. papillatum Farl.^° occurs on Alfilaria in California. Other species of Synchytrium are found upon dandelion, CEnothera, Geranium, Amphicarpa, Ornithogalum, clo- ver, elm, etc., but as yet are not of economic importance in America. Fig. 43.— Gail of S. vaccinii. After Shear. 72 THE FUNGI WHICH CAUSE PLANT DISEASE Pycnochytrium Schroter (p. 70) Only resting spores are known. In germination their proto- plasmic contents emerges and forms a sporangial sorus. P. anemones (D. C.) Schr. is common on various species of Anemone; P. globosum (Schr.) Schr. on the violet, blackberry, maple, etc. None of the species are of any considerable economic importance. Cladochytriaceae (p. 67) A branching mycelium runs through or between the cells of the host drawing nourishment from many cells. Sporangia are either apical or intercalary and contain uniciliate zoospores. Resting spores are also produced. There are about a half dozen genera and some thirty species. Key to Genera of Cladochytriaceae Resting spores onlj^ known 1. Physoderma. Swarm spores only known Intracellular and endophytic Swarm spores at first ciliate, becoming amoeboid 2. Cladochytrium, p. 72. Swarm spores not becoming amoeboid 3. Pyroctonium, p. 73. Living free among the hosts Sporangia opening by a pore 4. Amoebochytrium. Sporangia opening by a lid 5. Nowakowskiella. Cladochytrium Nowakowski-^ The genus contains about ten species of intercellular parasites with branched mycelial threads. The zoosporangium is globose, and opens by a distinct mouth which develops a tube for the escape of the zoospores much as does Olpidium. Resting spores are not known. THE FUNGI WHICH CAUSE PLANT DISEASE 73 The most important species are C. tenue Nowak. on Acorus and Iris; C. graminis Busg. on various grasses, C. violae Berlese on violets.-^ C. viticulum Pru.^ and C. mori Pru.-'* have been described on grape and mulberry, but further study is very desirable. C. brassicae E. & B.-'' is described from dead leaves of cab- bage. C. caespitis G. & M.^^ occurs in France on Lolium. Pyroctonium sphaericum Pru.-^ was reported in 1894 as the cause of wheat disease in France but has not since been found. Oochytriaceae (p. 67) The plant body is either an undifferentiated cell or a well de- veloped mycelium; reproduction by means of asexual swarm spores and sexual resting spores. Of the three genera only one is of economic importance. Key to Genera of Oochytriaceae Mycelium entirely lacking 1. Diplophysa. Mycelium present Mycelium producing a single gametan- gium 2. Polyphagus. Mycelium producing several gametangia 3. Urophlyctis, p. 73. Urophlyctis Schroter Mycelium endophytic, producing zoosporangia on the surface of the host and thick- walled oospores within the tissues; zoospores uniciliate. The genus contains some half dozen species all of which are parasitic on higher plants. XJ. leperoides (Sacc. & Trab.) Magnus -^' -^ causes "beet root tumor," in North Africa and Western Europe. The rootlets of the upper portion of the root are attacked and develop tumorous growths, sometimes as large as a walnut. The infection is super- 74 THE FUNGI WHICH CAUSE PLANT DISEASE ficial and does not extend to the fleshy tap root. The develop- ment of the spores is the typical method for the genus, the an- theridium persisting at the base of the oogonium and retaining its hyphal connection, while the oogonium becomes free just before conjugation. The oospores are subglobose, depressed on one side, smooth, brown, 45-50 x 30 n. U. pulposa (Wallr.) Schr., a closely related species occurs on the aerial portions of Chenopo- dium and Atriplex. U. alfalf« Mag.^°' ^"' "^' ^^i' ^"^ causes a crown gall of alfalfa in America and Europe. The dis- ease is quite similar to that de- FiG. 44.— Urophiyctis pulposa. a, zoo- scribed above for the beet sporangium; h, zoospores; c, oospore formation; d, mature oospores. ' After Schroter. U. trifolii (Pass.), Mag., a closely related species, forms small, glassy, globose pustules on the leaves and petioles of various species of clover in Europe. U. hemispherica (Speg.) Syd.^^ in South America, U. krieger- iana Mag.^^ in Europe and U. pluriannulata (B. & C.) Farl.^- in America form Synchytrium-like galls on various umbelliferous genera. All may belong to the same species. U. major Schr. and U. rubsaameri Mag. infect respectively the leaves and the roots of Rumex. Saprolegniales (p. 66) Asexual reproduction is mainly by biciliated spores formed in large numbers in sporangia of various shapes. Sexual spores, often apogamous, are produced in most genera, much after the fashion of those of the Peronosporales except that more than one oospore is frequently formed in one oogonium. ^^" The order consists of fifty or more species, mostly parasites or saprophytes upon aquatic organisms. One species of the genus Achlya causes serious disease in young fish. There are three families: THE FUNGI WHICH CAUSE PLANT DISEASE 75 Key to Families of Saprolegniales Vegetative mycelium of thick tubular hy- phae; aquatic; zoosporangia cylindrical not much thicker than the mycelium Filaments uniform, not constricted 1. Saprolegniaceae. Filaments constricted regularly 2. Leptomitaceae. Vegetative mycelium of thin hyphse, mostly parasitic or saprophytic on plant tis- sues; zoosporangia much broader than the mycelium, mostly globular 3. Pythiaceae, p. 75. Dictyuchus Leitgeb. This genus of the Saprolegniaceae contains the only parasite genus in the first two families. Sporangia cylindric or clavate, swarm-spores becoming walled within the sporangium and emerging singly through its lateral walls. The genus is usually saprophytic but, D. monosporus Leit. is said by Halsted to be a serious hyacinth enemy. ^"^^ The other members are mainly on dead or diseased insects or other animals that are in water or are on diseased algae or in water- sHme. Pythiaceae "^ This family shows affinity with both the Peronosporales and the Saprolegniales and is sometimes classed with the one, some- times with the other. It consists of three genera and about twenty species characterized by a mycelium of very delicate hyphae which show no differentiation into sterile and fertile regions. The species are either aquatic or terrestial; in the latter case they are soil fungi that grow to maturity upon seedlings. When of aerial habit the sporangia become conidial in character, that is, they are detached from the hypha before the discharge of the zoospores. Zoosporangia elongate 1. Nematosporangium. Zoosporangia spherical or oval, not linear Zoospores formed outside of the zoospo- rangia 2. Pythium, p. 76. Zoospores formed within the zoospo- rangia 3. Pythiacystis, p. 77. 76 THE FUNGI WHICH CAUSE PLANT DISEASE Pythium Pringsheim ^^ (p. 75) The mycelium is found in abundance in and about the infected tissue as fine, branched continuous threads. These, in the terrestial Fig. 45. — Cucumber seedlings. Pots 5, 6, and 8 inoculated with Pythium. Pot 7, Control. After Atkinson. species, bear conidia on branches which are of the same character as the mycehum itself. The conidia germinate either by a rupture of the wall or by the formation of a beak-like process through which the protoplasm is extruded, after which it becomes differentiated into zoospores. Gemmae, very like the conidia in ap- pearance, are also produced. The oogonia are quite like the conidia and gemmae in structure but develop oospores within. The oogonium is at first multinucleate but as the oosphere matures all of the nuclei except one migrate toward the periphery, the peri- plasm, or degenerate in the ooplasm, re- sulting at maturit}^ in an uninucleate egg. This is fertilized by one nucleus from the antheridium. No sperm is differentiated, Fig. 46. — Fertilization in Py- thium, showing oogonium, antheridium, oospore, peri- plasm and the cf and 9 nuclei. After Miyaki. THE FUNGI WHICH CAUSE PLANT DISEASE 77 and the contents of the anthoridium are carried over to the egg by a fertilizing tube. Members of the genus are aggressively parasitic only under most favorable environmental conditions of heat and moisture. Some sixteen species are known. P. de baryanum Hesse, is most com- mon ^^'^^ as the cause of "Damping Off." Zoosporangia or "conidia" globose to elliptic, usually papillate, 20-25 /x; gemmae similar in form and size; oospores globose, hyaline, smooth, 15-18 /x. P. intermedium de Bary, causes a "damping off" of fern prothalia,^^ P. gracile Schenck, a rot of ginger; ^^ P. palmivorum Butler, a palm disease in India Fi(!. 47. — P. citriophora; dn- vclopmciit (if s\v;irnispores from sporaiiKiii. After Smith and Smith. 3C. :> 1 Pithiacystis, Smith & Smith (p. 75) The sporangiophore is delicate; septate; and bears numerous sporangia sympodially. These produce many biciliate zoospores internally. No oospores have been seen. Only one species is known. P. citriophora Sm. & Sm.^^- ^^ Parasitic on lemons, the sterile mycelium inhabiting the rind; spores normally formed in the soil near infected fruits ; sporangia ovate or lemon-shaped, papillate, 20-60 x 30-90 jjL, averaging 35 x 50 n, borne sympodially; zoospores 10-16 /x. at first elongate, becoming rounded and bearing two lateral cilia. This was first noted by Smith and Smith '''•'• ^^ on rotting lemons in California. Infection by pure cultures proved that the fungus was the true cause of the rot. Peronosporales (p. 66) These fungi constitute an order characterized by a richly developed, branching, non-septate, usually coarse, mycelium of Fig. 48. — Sporangiophores and spo- rangia of Pythiacystis. After Smith and Smith. 78 THE FUNGI WHICH CAUSE PLANT DISEASE strictly parasitic habit. The mycehal threads in most genera wander between the host cells and draw nutriment from them by short branches, sucking organs (haustoria), (Fig. 49) of various forms, which penetrate into the victimized cell. In one genus only, Phytophthora, does the mycelium grow directly through cells. Two kinds of spores are produced, sexual and asexual. The sexual spores result from the union of two unlike gametes, the egg (oosphere) and sperm, borne respectively in the oogonium and antheridium. Each oogonium bears a solitary oosphere. Fertilization is accom- plished by means of a tube from the anther- idium and penetrating into the oogonium. The sexual spores are thick walled, re- FiG. 49. — Haustoria of a . , , , ,, . , ,. , Peronospora. After sistant, and usually require a long time to ^°P^- reach maturity. They are, therefore, often called "resting spores." In germinating the sexual spores pro- duce either germ tubes or develop directly into zoosporangia. The asexual spores are conidia. They are borne on conidio- phores which arise from the mycelium and which may be short or long, simple or branched, subepidermal or superficial accord- ing to the habit of the species. The conidia in various genera germinate by three methods, (1) a germ tube is sent out by the conidium, (2) the entire protoplasmic contents of the spore passes outside the spore wall and then forms a germ tube, or (3) the conidium by internal division breaks up into zoospores. Key to Families of Peronosporales Conidiophores, short, thick, subepidermal, conidia catenulate 1- Albuginaceae, p. 78. Conidiophores, longer, superficial, simple or branched, conidia not catenulate 2. Peronosporaceae, p. 82. Albuginaceae There is a single genus. Albugo (Persoon) Roussell. This genus of about fifteen species is entirely parasitic upon flowering plants. THE FUXGl WHICH CAUSE PLANT DISEASE 79 causing the "white rusts." The conidia are borne in white bUstcr-Uke sori under the raised and finally ruptured epidermis of the host. The conidiophores are short, club-shaped, arranged Fig. 50. — Albugo. A, section through a sorus showing epidermis, conidia, conidiophores and mycelium; B, conidiophores and conidia; C, myce- lium and haustoria. After Bergen and Davis. in alusters; the spores are borne in basipetal succession and remain attached in rather long chains unless disturbed. The mycelium is very fine, intercellular and penetrates the cells by globular haustoria. The rudimentary oogonium is multi- nucleate and filled with uniform proto- plasm. As the oogonium grows older the protoplasm within differentiates into two parts, the inner part of dense protoplasm, the oosphere, and the outer part less dense, the periplasm.^^ Figs. 51, 53, 54. During this process the nuclei enlarge, undergo one or two mitoses, Fig. 54, and in some species all the nuclei except one pass to the periplasm. In other species the Fig. 51.— Multiple fertilization ..1 • ij.' 1 . . . •. in A. bliti. Antheridial tube oosphere is multmucleate at maturity. discharging sperms. After The latter type is fertilized by nu- Stevens. merous nuclei from the antheridium, the former by a single nu- cleus.^^'^'*' ^- After fertilization the oosphere matures to an oospore. 80 THE FUNGI WHICH CAUSE PLANT DISEASE The globular oospores fall into two classes; ^^ first tuber- culate or ridged; second, reticulated. These are illustrated in Fig. 52. aw.w. 07. Fig. 52. — Oospores of Albugo. 1. A. Candida. 2. A. tropica. 3. A. ipomoesD- panduranae. 4. A. Icpigoni. 5. A. swertia;. 6. A. tragopogonis. 7. A. bliti. 8. A. platensis. 9. A. occidentalis. 10. A. portulacae. After Wilson. The conidia in germination usually produce several ovate zoospores with two unequal, lateral cilia. After a brief period of motility they became walled and produced germ tubes capable of infecting susceptible hosts. The oospores after a period of rest THE FUNGI WHICH CAUSE PLANT DISEASE 81 germinate in a similar manner. Conidia germinate freely only if they are chilled.^" A. Candida (Pers.) Roussel. '^ Sori on all parts of the host except the roots, white or rarely light-yellow, prominent and rather deep- seated, variable in size and shape, often confluent and frequently producing marked distortion of the host; conidiophores hyaline, clavate, about 35^0 x 15-17 n; conidia, globular, hyaline, with uniformly thin walls, 15-18 /x; oospores, much less common than conidia, usually confined to stems and fruits, chocolate-colored. Fig. 53. — A. bliti, young oogo- nium and antheridium show- ing nuclei. After Stevens. Fig. 54.— a. bliti. showing differ- entiation of ooplasm and periplasm, the nuclei in mito- s is. After Stevens. Fig. 55. — A. bliti, an- theridium showing the multinucleate tube. After Ste- vens. 40-55 fjL; epispore thick, verrucose, or with low blunt ridges which are often confluent and irregularly branched. This is the most widely distributed and most common species of the genus. It occurs throughout the world on a large number of cruciferous hosts, and often gives rise to very pronounced hypertrophy. Practically all cultivated crucifers, cabbage, radish, turnip, etc., are subject to attacks of this fungus. In Europe the caper and mignonette are attacked by the same species. It has been reported in New York on Tropoeolum.'*^ A. ipomoeae-panduranae (Schw.) Sw."*^' ^^" Sori amphigenous or caulicolous, white or light yellow, prominent, superficial, 0.5- 20 mm., rounded, often confluent and frequently producing marked distortions of the host; conidiophores hyaline, clavate. 82 THE FUNGI WHICH CAUSE PLANT DISEASE unequally curved at base, 15 x 30 /z; conidia hyaline; short- cylindric, all alike or the terminal more rounded, 14-20 x 12-18 ^u; the membrane with an equatorial thickening, usually very pro- nounced. Oosporic sori separate from the conidial, caulicolous, rarely on petioles, 1-2 x 5-6 cm. or even more, causing marked distortion; oospores light yellowish-brown, 25-55 n; epispore papillate or with irregular, curved ridges. Common throughout the world on various species of Convol- vulaceae, morning glory, moon flower, sweet potato, etc., although causing but little damage. A. occidentalis G. W. W., reported by Pammel ''° on the beet has been collected but once. A. portulaceae (D. C.) Kze. on purslane ^^ and A. bliti (Biv.) Kze."*'- occur on Amaranthus and related plants. A. tragopogonis (D. C.) S. F. G.^^' '^^ Sori hypophyllous or caulicolous, prominent, deep-seated, white or yellowish, pul- verulent, rounded or elongate, 1-3 x 1-8 mm; conidiophores hyaUne, clavate, about 12-15 x 40-50 fx; conidia, 12-15 x 18-22 /x; light yellow or hyaline, short-cylindric, the terminal larger and less angular than the others, membrane with an equatorial thick- ening; oospores produced in stems and leaves, dark brown or almost black at maturity, opaque, 44-68 ^u, epispore reticulate, areolae 2 n; wing bearing papillate tubercles at its angles. A cosmopolitan species of less economic importance in America than in Europe attacking a wide range of hosts of the Compositae. Salsify is the chief economic host. Peronosporaceae (p. 78) The members of this family, producing the diseases commonly known as the "downy mildews," have been long known and much studied. They contain many important plant pathogens. The globular oospores are in general indistinguishable from those of the Albuginacese but the conidiophores are quite different from those of that family, being aerial instead of subepidemal. In most cases they are branching and tree-like, Fig. 63, but in a few genera they are short. The oospore in such genera as have been studied (Peronospora ^^ Sclerospora ^^) is formed as in Albugo resulting when mature in an uninucleate egg surrounded by a THE FUNGI WHICH CAUSE PLANT DISEASE 83 periplasm bearing the degenerate supernumerary nuclei. Fer- tilization is as in the Albugos that have an uninucleate ggg 41, 44, 52, 53 The family has suffered many revisions of classification and much renaming of genera. Plasmopara and Peronospora are especially rich in a masquerade of names."*^' •'^■*'^^' Key to Genera of Peronosporaceae ^ Conidiophores scorpioid-cymosely branched ; conidia germinating by zoospores 1. Phytophthora, p. 84. Conidiophores simple, monopodially or dichotomously branched. Conidiophores simple or monopodially branched; conidia germinating by zoospores or by a plasma Conidiophores simple or irregularly branched 2. Kawakamia, p. 89. Conidiophores regularly branched Conidiophores with the main axis indurate, the lateral branches reduced and basidia-like 3. Basidiophora, p. 89. Conidiophores with the main axis not indurate, the lateral branches developed normally. Conidiophores fugacious, stout, sparingly branched; oospore permanently united to the wall of the oogonium 4. Sclerospora, p. 89. Conidiophores persistent, slender, usually freely branched; oo- spore free from the wall of the oogonium Branches of the conidiophore apically obtuse 5. Plasmopara, p. 90. Branches of the conidiophore apically acute 6. Peronoplasmopara,p.93. Conidiophores dichotomously branched; conidia germinating by a germ tube. Conidiophores with subapical disk-like enlargements from which the ul- 84 THE FUNGI WHICH CAUSE PLANT DISEASE timate branchlets arise radially; germ tube produced from the apex of the conidia Conidiophores without subapical en- largements; conidia germinating from the side 8. Peronospora, p. 95. 7. Bremia, p. 95. Phytophthora de Bary (p. 83) This genus is of especial interest on account of its one exceed- ingly destructive representative, P. infestans, which occupies an historic position in phytopathology as one of the earliest of para- sitic fungi to receive study in any way complete or adequate; study moreover which did much to turn attention and interest toward plant pathology. A distinctive character is that the conidiophores have irregular thickenings below the apparently lateral conidia. The conidio- phore is at first simple and bears a single apical conidium, after the production of which a lateral branch arises below the conidium and grows on in such a way as to give the first conidium a lateral appearance. This process is, in some species, repeated until a large scorpioid cyme is produced. The genus contains seven or eight species, all parasitic. The mycelium is much branched, non-septate, hyaline; the conidiophores arise singly or in groups from the stomata, or break through the epidermis; conidia oval, papillate; zoo- spores oval, biciliate, escaping by rupture of the papilla; oospores, when present, with the epispore more or less ridged. P. phaseoli Thax.^^"^^ Mycelium well de- veloped, intracellular; conidiophores single or in clusters from the stomata, simple or branched *below, apparently simple above but really one to many times cymosely branched; conidia oval or elliptic, papillate, 35-50 x 20-24 n; germination by about fifteen zoospores. Oogonia in the seed coats or cotyledons of seeds, rarely in the pods, thin walled, slightly folded; subspherical 23-28 n; oospores spherical or Fig. 56. — Structural de tails of P. phaseoli After Thaxter. THE FUNGI WHICH CAUSE PLANT DISEASE 85 86 THE FUNGI WHICH CAUSE PLANT DISEASE subspherical with smooth, moderately thick - walls, hyaline or light yellow, 18-26 ix. It was described on lima beans in 1889. The methods of infection were studied by Sturgis ^" who showed that spores are carried to the basal portion of the style and ovary by visiting insects. Oospores were described and extensive arti- ficial culture experiments made by Clinton ^^ who first grew the fungus successfully in pure culture on corn-meal-agar, and other media, on which oospores were produced in abundance. The species is unique within the genus on account of the single conidia which are borne at the apex of apparently simple conidio- phores but subtended by several enlargements of the kind so characteristic of the genus. P. infestans (Mont.) de Bary.^"' ^'"'^ ^46-148 Mycelium well developed, probably perennial; conidiophores single or in groups of 2-4 from the stomata; scorpiose-cymosely branched; conidia 27-30 x 15-20 ix, ovoid, germinating by about six to sixteen zoospores. On diseased solanaceous hosts, particularly the potato and tomato,^^ this species is very destructive. It was first described ^^,====3. in 1845 as a Botrytis and /^j^<~Px\' ^^s since been the subject C-fe^'"^' ■ !^ of many extensive papers. \l^^-i;-^^/7 "* The conidiophores are \^^^^/^ X'^rS abundant on the lower sides .\ -^ /'^. '/ of infected leaves near the ^"■■•^jl^^^^i^v \^^s>-^'^"Y^ invasion line. The myce- /^P^^'' "'^^ \ \?T \mm migrates between the ^" /ll«3^- \ V ^^^^^ piercing them with ^^: '^^ A \ haustoria. ^%i^^ji^ '/\ \ The existence of oospores Fig. 58. — Young and mature oospores of is a mUch Controverted p. phaseoli. After Clinton. • x j.i, j. j. pomt; the structures re- ported by Smith ^""^^ as oospores probably belonged to some other fungus. Recently Jones ^^ found peculiar thick- walled bodies, somewhat resembUng oospores, in undoubtedly pure cultures of P. infestans. Whether they are oospores is not known. Clinton has recently announced ^^ that he, in pure cultures, has obtained "absolutely perfect oogonia, antheridia and even oospores-" The THE FUXGI WHICH CAUSE PLANT DISEASE 87 oval, flattened biciliate zoospores which emerge from the conidia, swim about, come to rest, develop a wall, then produce a germ tube. Direct germination by a germ tube also occurs rarely. In- FiG. 59. — P. infostans; 1, section showing conidiophores aiul conidia- formation; 5, germination of a conidia. After Scribner. fection is brought about by the germ tube, either by penetrating through stomata or directly through the epidermis. The walls and contents of parasitized cells are browned. When this fungus is alone on the tubers dry rot is induced, but invasion of numerous saprophytic fungi and bacteria usually turns this into a disagreeable wet rot. Tuber infection occurs largely from 88 THE FUNGI WHICH CAUSE PLANT DISEASE conidia washed into the soil by rain; possibly sometimes by the mycelium migrating by way of the stem. The fungus was extensively studied by Jones in pure culture and a decided difference in luxuriance of growth was observed on blocks cut from different varieties of potatoes, Fig. 57. The mode of hibernation is not thoroughly known but undoubt- edly hibernation occurs in part in live mycelium in infected tubers.™ The conidia are short-lived, especially when dry. P. omnivora de Bary. Conidiophores simple or branched; conidia ovoid or lemon-shaped, 50-60 or even 90 x 35-40 fx, ger- minating by as many as fiftj'^ zoospores; oospores smoothish or wrinkled, light-brown, transparent, 24-30 /x. This species which includes forms previously described as P. cactorum (Lebert & Cohn) Schr., P. fagi Hartig, and P. sempervivi Schenk is found upon seedlings of some fifteen families ranging from Pinacse to the higher Angiosperms. It is of considerable economic importance in Europe especially in the seed beds of the forester. Recently it has been found on ginseng in Japan and the United States.^^ The same fungus is credited with destructive rotting of apples '^^ and pears "^^ in Europe and with causing two wide-spread tropical diseases, the cocoa pod rot and a palm disease. From the studies of de Bary ^^ and from the nature of the more recent outbreaks cred- ited to this fungus it appears that P. omnivora is a composite species which will eventually be segre- gated. Indeed segregation has already been begun. Coleman " has described the palm in- fecting fungus of India as P. omnivora var. arecae while Maub- lanc^^ has gone further and described the cocoa disease as P. faberi. See also "• ^^" P. syringae recently described by Klebahn is a closely related species, which is very destructive in the propagating beds of the lilac in Germany. Fig. 60. — Formation of swarm-spore of Phytophthora. After Smith. THE FUNGI WHICH CAUSE PLAX'I' DISEASE 89 P. agaves Gan.^^ occurs on the Agave in Mexico. P. nicotiana v. B. d H.^° is also closely related to P. omnivora, but culture work shows it to be rather fastidious in its choice of host as it attacks only tobacco seedlings. P. calocasiae Rac. occurs on Calocasia antiquorum in the Orient. An undescribed species on Castor is also reported.**^ Kawakamia Miyabi (p. 83) Mycelium slender, copiously branched; conidiophores single or in groups of 2-5 or more from the stomata, simple or sometimes irregularly branched, but branches never arising near the conidia. Conidia usually upon a slender pedicel cell, lemon-shaped, ob- tusely tipped, contents and wall colorless, germination normally by zoospores; zoospores oval, flattened and laterally biciliate; oospores spherical, smooth. A single species, K. cyperi (M. & I.) Miyabe,^^ which was intro- duced from Japan into Texas in imported plants of a sedge, Cyperus tegetiformis. The species is very destructive in Japan. Both conidia and oospores were produced in the Texan material.^- Basidiophora Roze & Cornu (p. 83) B. entospora R. & C. occurs on species of Erigeron and culti- vated aster in Europe and America. Sclerospora Schroter (p. 83) This genus differs from all other Peronosporales in the pre- ponderance of its oospores; these are the conspicuous stage, while the conidiophores and conidia are few, small and evanescent. There are about five species. Mycelium much branched, with small vesicular haustoria; conidiophores erect, solitary or in groups of two or three, fugaceous, low and stocky, sparsely branched, the branches also stocky; conidia elliptic or globose-elliptic, hyaline, smooth; oospores globose, intramycelial, the epispore broA\Ti, irregularly wrinkled, permanently united to the persistent wall of the oogo- nium. 90 THE FUXGI WHICH CAUSE PLANT DISEASE S. graminicola (Sacc.) Schr.,''-' ''^ infectsleaves and inflorescences, the oospores causing marked distortion of the latter and rapid disintegration of the former; conidiophores 100 x 10-12 (x, conidia 20 X 15-18 m; oogonium wall thick, 4-12 n, at maturity 30-60 /z in diameter, reddish-brown; oospore pale-brown, 26-36 fx. The conidial phase is not prominent, while the oospores by their disintegrating effect upon the leaves of the host, render the plants quite conspicuous and closely simulate the habit of a brown smut. Fig. 61. — S. graminicola. Conidiophores and co- n i d i a ; germinating conidia and zoo- spores. After Butler. Fig. 62. — S. Kraniinicola, oo- gonium, oospore and an- theridium in section. Af- ter Stevens. On millet (Setaria italica), pearl millet, fox tail and corn; in India of considerable economic importance.^^ S. macrospora Sacc. has been reported in com tassels and on wheat in Italy and the United States.^^' ^^ Conidia unknown; oogonia embedded firmly in the tissue of the host, not causing disintegration as in S. graminicola; oospores light yellow, smooth, 60-65 fi. Plasmopara. Schroter (p. 83) 134 The tree-like, branching conidiophores, Fig. 63, are common to this genus, Peronospora, Peronoplasmopara and Bremia, and unlike the conidiophores of Phytophthora they are completely formed before they begin to bear spores. Mycelium branched; haustoria simple; conidiophores erect. THE FUNGI WHICH CAUSE PLANT DISEASE 91 solitary or fasciculate, from the stomata of the host, monopodi- ally branched, the branches arising at right angles to the main axis, as do also the secondary branches (at least never appearing truly dichotomous) the ultimate branches apically obtuse; conidia globose to ovoid, hyaline or smoky, germinating by zoospores or the entire protoplasmic mass escaping and then sending out a germ tube; oospore globose yellowish-brown, the epispore va- riously wrinkled sometimes appearing somewhat reticulate; oogo- nium persistent, but free from the oospore. P. viticola (B. & C.) B. & d T.,''- ^^' "^' '''' ''' first collected in 1834 by Schweinitz and regarded as a Botrytis was first published in 18515 Hypophyllous, caulicolous, or on young fruits, covering the infected areas with a white downy growth; on the leaves epiphyl- lous discoloration yellowish ; on the fruit often causing a brown rot without producing conidia; conidiophores fasciculate, 250-850 x 5-8 fi, 4-5 times branched, the ultimate branchlets about 8 fi long; conidia ovate-elliptic, very variable in size, 9-12 x 12-30 n; oospores 30-35 ju, epispore brown, wrinkled, or almost smooth; oogonium thin-walled, hyaline or light yellowish-brown. The mycelium is found in all diseased tissues except the xylem. The conidiophores issue from stomata. The conidia germinate readily in water, producing in about three-fourths of an hour biciliate zoospores. These after fifteen to twenty minutes activity cease motion, round off, become walled, then germinate by a tube. This bores through the epidermis and develops into the internal mycelium. Infection is almost exclusively from the lower side of the leaf .^^ Oospores are much more rare than conidia but are often found in autumn, sometimes two hundred to a square millimeter of leaf surface. Though hibernation is doubtless chiefly by oospores it has been shown that the mycelium can perennate in old wood, and even form oospores therein. The fungus is dependent on abundant moisture. P. nivea (Ung.) Schr. attacks various species of umbellifers in- cluding the parsnip and carrot. It has been reported in America only from the region of San Francisco. P. halstedii (Farl.) B. & d T. This form is quite variable and should perhaps be separated 92 THE FUNGI WHICH CAUSE PLANT DISEASE into several distinct species. It is limited to the Compositse, Helianthus and Madia being the only hosts of economic impor- tance. Hypophyllous; conidiophores fasciculate, slender, 300-750 m, 3-5 times branched, ultimate branchlets 8-15 fx long, verticillate Fig. 63. — P. viticola. A, seotion of a leaf with conidiophores emerg- ing from a stoma; C, formation of swarm spores; D, formation of oospores. After Millardet. below the apex of the branching axis which is frequently swollen and ganglion-like; conidia oval or elliptic, 18-30 x 14-25 /x; oospores 30-32 ix, epispore yellowish-brown, somewhat wrinkled. P. ribicola (Schr.) Schr. grows on various species of currants in Europe and America but is probably of but slight economic importance. THE FUNGI WHICH CAUSE PLANT DISEASE 93 P. obducens (Schr.) Sclir. occurs on Imputiens, both wild and cultivated, in North America, Europe and Asia. P. pygmea (Ung.) Schr. on various Kanunculacese, including Aconitum in Europe and cultivated Hepaticas in America,^'' is of little economic importance. Peronoplasmopara (Berlese) Clinton (p. 83) There are three species which have been variously designated as Peronospora, Plasmopara, Pscudoplasmopara and Peronoplas- mopara. The genus combines colored conidia and zoosporic germi- nation with a type of conidiophores intermediate between those of Peronospora and Plasmopara. Mycelium much branched, haustoria small, usually simple; conidiophores pseudo-monopodially branched, the ultimate branch- lets acute, the primary arising at acute angles; conidia colored, elliptic, conspicuously papillate both apically and basally; oospores thin-walled, smooth or roughened; oogonium thin-walled. P. celtidis (Waite) Cl.^^ is unique in the family as the only species infecting dicotyledonous trees. It occurs on hackberry in the region about Chesapeake Bay, also in Japan. P. humuli Miy. & Taka ^- causes a serious hop disease in Japan. It has recently been found by Davis ^^ on wild hops in Wisconsin. P. cubensis (B. & C), Cl.^^'^^' ^^^ Hypophyllous, rarely amphigenous; discoloration of the host yellowish, or water-soaked; conidiophores 1-2 rarely more from a stoma, 180-400 x 5-9 fi, 3-4, rarely 2-5 times branched, the ulti- mate branchlets recurved; apically acute, 5-20 fj. long; conidia gray, brownish or smoky, ovoid to ellipsoid, papillate, 20-40 x 14-25 fi; oospores spherical, yellowish, warty-papillate, 30-43 fi, maturing in the decaying leaves. The mj^celium abounds in the spongy parenchyma. The conidiophores emerge through stomata, or rarely directly through the cuticle, near the invasion line of the fungus. Fresh conidia germinate in water in two to four hours forming flatfish zoospores with one anterior and one posterior cilium. The zoospores later become spherical, walled and develop a germ tube. These germ tubes enter the host through the stomata or directly through the cuticle from cither above or below. Moist weather is favorable to 94 THE FUNGI WHICH CAUSE PLANT DISEASE the fungus in that conidia are produced more abundantly and retain their power of germination longer when moist. Disease spots appear two or three days after infection; conidia same nine or ten days after infection. The species is perennial in Florida ^'^ and spreads northward as the season advances, reaching Ohio and New York by late summer Fig. 64. — P. cubensis: .3. Conidiophore wjth young and old conidia. 5. Conidium. 6. Conidium germinating. 11. Zoospores. 18. Infection through a stoma. After Clinton. or early autumn.^^ For a series of years after its discovery it was not well known even scientifically, its first serious outbreak being about 1889.^^ It appeared in Japan about the same time ^°° and is now known to be almost cosmopolitan. The oospores have been found only by Rostewzew and have not been seen in America. A wide range of wild and cultivated cucurbits is infected, among THE FUNGI WHICH CAUSE PLAXT DISEASE 95 them the pumpkin, squash, cucumber, muskmelon, watermelon, gourd, in fact according to the work of Selby ^"^ any cucurbit ap- pears Uable to attack. CHnton infected muskmelons with spores produced on cucumber. The fungus is especially prevalent on cucumbers raised under glass. Bremia Kegel (p. 84) As in Peronospora except that just below the ends of the conidio- phore branches there are pronounced swellings from which spring radially a number of short branches each bearing an ovate, papillate conidium. The conidia germinate by apical germ tubes. There is only one species. B. lactucae Kegel is found on lettuce and several other Compositse.^°^ It is more in- jurious in Europe than in America. Hypophyllous or amphigenous, causing discoloration, then wilting of the host; conid- fig. 65.— B. lactucse. iophores produced singly but in great abun- ^^^^^ Tubeuf. dance, much branched; conidia ovate, 16-22 x 15-20 fx; oospores small, 26-35 fi, light brown, the epispore wrinkled. Peronospora Corda (p. 84) 52 This genus of some sixty species contains several aggressive parasites. Its conidiophores are much like those of Plasmospara but with more tendency to dichotomous branching and to more graceful habit; the apices are acute. Mycelium well developed, haustoria filiform, simple or branched; conidiophores dichotomously 2-10 times branched at acute angles, ultimate branchlets acute, more or less reflexed; conidia hyaline or colored, papillate, germinating directly by lateral germ tubes; oospores globose, reticulate, tuberculate, wrinkled or smooth. P. parasitica (Pers.) De Bary.^^ This is often associated with Albugo Candida, giving it the appearance of a parasite on that fungus. Almost all species of Cruciferae are subject to attack, among them cabbage, cauliflower, radish, collards, turnips, horse- 96 THE FUNGI WHICH CAUSE PLANT DISEASE radish, and others of minor economic importance. It is cos- mopoHtan in distribution. The fungus covers any green part of the host with a dense white growth, often causing hypertrophy especially in oospore forma- tion; conidiophores 200-300 x 10-12 ii, bushy branched, stout, deliquescent, with 5-8 main branches, each from 3-7 times branched, ultimate branchlets slender, more or less curved, usually arising at acute angles, about 12-15 x 2-3 ju; conidia broadly elliptic, bluntish, often becoming globose, about 12-22 x 24-27 ;u, hyaline or very light; oospore globose, yellow-brown, 26-45 ix, epispore smooth or wrinkled; oogonium thick, color- less. P. efifusa (Grev.) Rab. causes a serious disease of spinach. ^"^ It also occurs on a wide range of weeds of the Chenopodiaceae. The species was formerly made to include all the effusae forms of the genus so that literature abounds with references to it on Viola, Plantago, Polygonum, etc. Hypophyllous, causing yellowish or brown- ish discolorations, the mass of conidiophores of a violet cast; conidiophores 150-400 x 7-9 ju, much branched, the ultimate branches at right angles, usually recurved, 8-15 x 3-4 ii] conidia ellipsoid to globose 17-18 x 22-24 jx, violet or smoky; oospores globose, 30-40 u, epispore light brown, more or Fig. G6. — P. cnusa on i i • i i i spinach. After Hal- less regularly wrmkled; oogonmm thm, ^ ^ ■ brown. P. schleideni Ung.^°^ was first described as aBotrytis in 1841. It was noted in America in 1872 by Taylor,^*^^ later by Trelease ^°^ and by many others. ^°^ A very complete description was given by Whetzel ^^^ in 1904 under the name P. schleideniana. The conidia in mass present a purplish tint. The conidio- phores usually emerge singly through the stomata. The slender, branched haustoria abound in the parasitized part often with their ends wrapped around the nuclei. In water the conidia THE FUNGI WHICH CAUSE PLANT DISEASE 97 germinate directly to form an infective tube (Fig. G7) which grows into the stomata. According to Whetzel conidia retain their germinating power only a few hours. Shipley believed them viable for a much longer time.'"'' Fertilization occurs much as in P. parasitica (Fig. G7) and the sexual spores, which abound, serve for hibernation. The}^ may live several years. It is found on onion, garlic, etc. (Allium sps.) everywhere, covering leaves with a dense growth; conidiophores, 3-6 times branched, 300-700 x 12-15 fx; branches 2-5, scattered, ultimate branchlets subulate, 15-20 /x, more or less recurved; conidia large, obovate to pyriform, basally papillate, 45-58 x 20-25 ju, the membrane violet; oospore globose, light-brown, about 30 fi, epispore smooth or slightly wrinkled. P. sparsa Berk, is parasitic on roses ^^ and constitutes a serious pest in Europe, though not so common in America. Hypophyllous, with a whitish growth; conidiophores about 9 times branched, the ultimate branchlets refiexed; conidia sub- elliptic, pale gray. P. trifoliorum de Bary. Hypophyllous, forming a dense grayish or dirty- white growth over the host; conidiophores slender, 360- 600 X 9-11 fi, 6-8 times branched at acute angles, the primary branches rather erect, the secondary more spreading, flexuose, more or less recurved, ultimate branchlets at right or obtuse angles, straight, subulate, 7-12 x 7-3 n; conidia globose to broadly elliptic, 15-20 x 18-36 n, violet; oospores globose, 24-30 /t, epispore light brown, smooth. It causes serious loss to clover in Europe. Species of related genera also suffer. Recently it has assumed a role of importance in America by its attacks upon Alfalfa ^^° on which it occurs from New York to California. It differs from P. viciae in the branching of the conidiophores, the lighter color of the spot and fungus, and the smooth oospores. P. viciae Berk. Hypophyllous or caulicolous, covering the host with a grayish-violet growth, epiphyllous discolorations yellowish or inconspicuous; conidiophores fasciculate, 300-700 x 9-11 n, 5-8 times branched, the main branches arising at acute angles, erect, the ultimate subequal, slightly flexuose, arising at right or obtuse angles, the lateral recurved, 10-17 x 2-3 n; conidia elliptic 98 THE FUNGI WHICH CAUSE PLANT DISEASE 11 14 Fig. 67.— p. schlcideni. 11. Mycelial threads between the large conductive cells of the leaf; (a) the mycelial thread; (b, b) branched or coiled haustoria; (c) branched haustorium wrapped about the nucleus. 1.3. Young conidiophorcs, (a, a) turn- ing toward the stoma, (b) ; (c) haustorium wrapped about the nucleus of the epidermal cell. 14. Mature conidiophore (a) with mature conidia, (c, c) ; (d) germ tube of conidium entering stoma. 15. Oospores, (a) mature oospore with old antheridiiim, (d) still attached; (b) mature oospore still inclosed in the old wall of the oogonium. After Whetzel. THE FUNGI WHICH CAUSE PLANT DISEASE 99 or obovoid, 15-20 x 21-28 n, light-violet; oospores small, 25-30 n, epispore yellowish-brown, with low, broad reticulations, areolae about 8 ju; oogonium thin, fugaceous, 32-40 /x. This fungus on ^'i('ia and related genera is sometimes quite Fig. 68. — A sporangium with a columella (Mucor). After Sachs. serious, particularly on vetch and peas in Europe, Asia and America. P. violae de Bary; on cultivated violets and the pansy in Europe and America,^^ forming discolored spots; foUicolous or caulicolous, with a pale violet growth, conidiophores fasciculate, short, 2-7 times dichotomously branched; ultimate branchlets short, sub- ulate, reflexed; conidia elliptic, short, apiculate, 20-22 x 15-18 ti, violet. 100 THE FUNGI WHICH CAUSE PLANT DISEASE P. dipsaci Tul. on teasel and Scabiosa in Europe and America and P. violacea Berk, on the flowers of species of Scabiosa in Europe are quite distinct from the preceding; P. schachtii Fcl. on beets kills seedlings in Europe. P. linarias Fcl. is on digitalis; P. cytisi Fig. 69. — Sporophores in the Zygomycptes. After De Bary, Brefeld, Cunningham, Schroter. Rost.^^'' ''- on species of Cytisus in Europe; P. arborescens (Berk.) de Bary on poppies, especially garden seedlings, in Europe and Asia. Species of less importance are: P. rubi Rab. on various species of Rubus in Europe and America; P. fragariae R. & C, usually cited as a synonym of P. potentillse de Bary, on the strawberry in France and America; P. trichomata Mas.^^'^' "^ the cause of a root rot of Colocasia THE FU\GI WHICH CAUSE PLAXT DISEASE 101 in the West Indies; P. Candida Fcl. on the primrose in Europe and upon non-economic Primulaceae in America; P. maydis Rac.^^^ the cause of a disease of corn in Java. [Its identity with Sclero- spora graminicola is suggested by the recent studies of that species by Butler.] P. vincae Schr. on Vinca minor in Europe; P. myoso- tidis de Bary on several species y<^ of forget-me-not and related genera in Europe and America ; P. cannabina Otth. on hemp in Europe and Japan; P. con- glomerata Fcl. upon alfilaria in Europe; P. ficariae Tul. on various species of Ranunculus both in the old and the new world; P. antirrhini Schr. on the snapdragon and related hosts in Europe; P. nicotianae Speg.^^^ on various ornamental species of Nicotiana in South Fig. 70.— Mucor: zygospore formation. America and California; P. va- '^"'^^'" ^"'^'^'^■ leria mellae Fcl. in Europe on Valerianella; P. Valerianae Trail on Valerian; P. dianthi de Bary on species of Dianthus in Europe; P. corallae Tranz. on Campanula in Europe; P. jaapiana "^ on rhubarb in Europe; P. phoenixae Tap. on Phcenix ^^'^ and an un- determined species on Para rubber. Mycelophagus castaneae Man,^^^ is an imperfectly described form which may belong either to the present group or to the Chytridiales. A serious disease of the chestnut in France is charged to it. Zygomycetes (p. 66) This group of fungi is readily distinguished from the Oomycetes by its isogamous sexual organs, when these are present. In the absence of sexual organs the general type of sporangium is usually sufficient mark of distinction for those who are even but slightly acquainted with the two groups. Tho mycelium, if young, serves to indicate relationship to the Phycomycetes. Older mycelium is often septate and would lead the unwary into errors of classification. 102 THE FUNGI WHICH CAUSE PLANT DISEASE Asexual spores are either in sporangia or are borne as conidia. The sporangium is usually with a columella. The spore-bearing stalks exhibit the widest diversity in shape and form of branch- ing, Fig. 69. Sexual spores (zygotes) are produced through the union of two like gametangia. (Fig. 70.) Though the cytology of zygote formation has not been completely studied it seems clear that the fertilization is multi-nucleate ^^"^ as in Albugo bliti and that the two uniting elements are ccenogametes. Key to Orders of Zygomycetes Asexual spores borne in sporangia which in some genera are reduced to conidia-like bodies 1. Mucorales, p. 102. Asexual spores true conidia borne singly at the apex of the conidiophores . ... 2. Entomophthorales, p. 107. Mucorales (p. 66) This order is comprised mainly of saprophytes, about twenty genera and one hundred fifty species; but includes a few forms which prey upon vegetation in a very low ebb of life, as cells of ripe fruit, tubers, etc., and a few species which are of especial interest as they grow upon other fungi. The sporangial stage is exceedingly common; the zygosporic much less so, very rare in the case of some species. Blakeslee ^-" has shown that in some species, though the two uniting sexual organs Fig. 71.— Phypomycetes .showing are to all appearances alike, the plants zygosporic lines at regions of . ,. ,. . contact between + and — are m reality dioecious; that a branch strains. After Blakeslee. ^^^^ ^^^ ^j.^^^ ^,^^^^^ produce sexual organs that will unite with other sexual organs produced upon the same plant. IVIoreover, there appears to be a differentia- tion of sex in that one plant, which may provisionally be re- THE FUNGI WHICH CAUSE PLANT DISEASE 103 garclcd as the male, unites freely with another plant, provisionally the female, but this male plant refuses to unite with any other plant which is capable of uniting with the female and all plants that can unite with the male refuse to unite with the females. In some species the plants of one sex show a more luxuriant vegeta- tive growth than do plants of the other sex. Key to Families of Mucorales. Asexual spores in typical sporangia, although in some genera few-spored Sporangium with columella; zygospores nakctl or thinly covered with out- growths of the suspensor 1. Mucoraceae, p. 103. Sporangium without a columella; zygo- spores closely covered by hyphae ... 2. Mortierellaceae. Asexual sporangia monosporic and conidia- like, sometimes accompanied by larger polysporic sporangia Sporangia of two kinds, polysporic and monosporic 3. Choanephoraceae, p. 106. Sporangia all monosporic; parasitic on other genera of Mucorales 4. Chaetocladiaceae. Sporangia simulating chains of conidia. . 5. Piptocephalidaceae. Of these families the second and fifth are pure saprophytes, while the fourth is parasitic upon other members of the order. Mucoraceae Mycelial threads all alike or of two kinds, one aerial, the other buried in the substratum, coenocytic during growth but septate at maturity; reproduction by asexual spores borne in sporangia and ])y zygospores formed by the union of equal gametes; spor- angiophores, simple or branched; sporangia variable, typically with a columella, and many spores but in some genera some of the sporangia are few-spored and without columellas; zygospores variable, smooth or spiny, borne on short branches of the myce- Hum. 104 THE FUNGI WHICH CAUSE PLANT DISEASE Key to Subfamilies and Genera of Mucoraceae Sporangial membrane cuticularized and per- manent above, thin and fugaceous be- low Subfamily I. Piloboleae. Sporangiophore of equal size throughout; spore mass not forcibly discharged . . . Pilaira. Sporangiophore swollen beneath the spo- rangium; spore mass forcibly dis- charged at maturity Pilobolus, p. 105. Sporangial membrane thin antl fugaceous throughout Sporangia all similar Subfamily II. Mucoreae. Mycelium differentiated into a colorless vegetative and a colored aerial re- gion Aerial mycelium stoloniferous, zygo- spores formed in th(> substratum Sporangiophores arising from the nodes 1. Rhizopus, p. 105. Sporangiophores arising from the internodes 2. Absidia. Aerial mycelium not stoloniferous; zygospores aerial Sporangiophores simple 3. Spinellus. Sporangiophores dichotomously branched 4. Syzygites. Mycelium imdiif erent iated Mycelium gray or brown; suspensors smooth Sporangiophores simple 5. Mucor, p. 106- Sporangiophores variously branched Sporangia borne apically on the sporangiophore antl its branches Zygospores formed from equal gametes 0. Calyptromyces. Zygospores formed from un- equal gametes 7. Zygorhynchus. Sporangia borne only on the lateral, circinate branches of the sporangiophore THE FUNGI WHICH CAUSE PLAXT DISEASE 105 Sporangia globular; columolla not constricted 8. Circinella. Sporangia pear-shaped ; colu- mella constricted 9. Pirella. Mycelium metallic; suspensors spiny 10. Phycomyces. Sporangia of two kinds, the primary many-spored; the secondary few- spored Subfamily III. Thamnidieae. Pilobolus crystallinus (Wigg.) Tode, a form with beautiful crystalline sporangia on yellowish, evanescent sporangiophores has been frequently noted as injuring or smudging chrysanthemum, rose and other leaves i'-i"i-- by its profuse discharge of spo- rangia. It is not, however, a parasite. Of the other genera the only ones of interest regarding plant disease are Rhizopus and Mucor. The others are saprophytes found on a great variety of substances, manure, fungi, and many other kinds of organic matter, Rhizopus Ehrenberg (p. 104) The sporangium v^all is not cutinized, and falls away. The sporangia are all of one kind and with columellas. The sporan- giophore is never dichoto- mous ; zygotes are found in the mycelium. The suspensor is without outgrowths. Twelve or fifteen species, chiefly sap- rophytes. R. nigricans Ehr. Aerial mycelium at maturity choco- ^ _„ _, . _^. , . '' . . Fig. 72. — Rhizopus. Diagram showing late-colored; rhizoids numer- mycelium and sporophorcs. After Coul- 1 p • ter, Barnes and Cowles. ous; sporangiophores lascicu- late, erect, aseptate; sporangia globose, l)lackish-olive, granular; columella hemispheric; spores gray to brown, subglobose or irregu- lar, 11-14 n; zygospore 150-200 n, epispore with rounded warts, black. This is the cause of soft rot of stored vegetal)les, particu- larly of sweet potatoes,^-^also of Irish potatoes,^^^ apples and pears; it causes death of squash blossoms ^-^ and is destructive to barley 106 THE FUNGI WHICH CAUSE PLANT DISEASE during malting. It is distinctly a wound parasite and is unable to force entrance through a sound epidermis. The richly branched mycelium which varies from very thin and hyaline to thick, coarse and slightly fuscous, is found throughout the rotten portion of the hast. After a period of luxuriant vegeta- tive growth hyphae protrude to the air, first through existing ruptures in the epidermis, later by rifts forced by the fungus itself. Sporangiophores then form in dense bush-like growths, each sporangiophore bearing one terminal sporangium. The sporangia are at first white, later black and contain very numerous spores. Spore formation has been closely studied by Swingle. ^-^ Aerial stolon-like liyphge reach out in various directions and at their points of contact with some solid develop holdfasts (Fig. 72) and a new cluster of sporangiophores. Zygotes are produced by union of two mycelial tips as is shown in Fig. 70. Orton ^-^ inoculated pure cultures of this fungus on sterile raw Irish potato and induced typical decay. He also noted that there was a difference in the rate of decay produced by strains of Rhizo- pus derived from different sources and that the most rapid decay of potatoes was caused by strains taken from rotting potatoes. R. necans Mas.^-" causes decay of lily bulbs in Japan. R. schizans Mas. is cited as the cause of split-stone in peach. ^-^ Mucor Linnaeus (p. 104) Mycelium all of one kind, buried in the substratum or grow- ing over its surface; sporangiophores scattered or not, simple or branched; sporangia globose; columella cylindric, pyriform or clavate; spores numerous, variable; zygospores globose, smooth or warty. Some thirty species, chiefly saprophytes. M. mucedo L. is destructive to beech nuts in winter. M. pyriformis Fisch and M. racemosus Fes. cause decay of fruits. Choanephoraceae (p. 103) Mycehum parasitic on living plants; sporangia of two kinds; macrosporangia globose, columella small, spin}', spores few, on THE FUXGI WHICH CAUSE PLANT DISEASE 107 simple or branched, erect sporangiophores; microsporangia clavatc, one-spored simulating conidia and borne in heads on the enlarged apices of umbellately branched sporangiophores; zygospores as in IMucoracae. A single genus, with three species. Choanephora infundibulifera (Curry) Sacc. and C. americana A. Alull occur on blossoms hi India and South America. A third species, C. cucurbitarum (B. & Br.) Thaxter, is the cause of decay of cucurbits especially pumpkins, in the eastern and southern states. ^-^ Entomophthorales (p. 66) This order is predominately one parasitic on insects. Some fifty species are known, only four of which are plant parasites. Asexual reproduction is chiefly by conidia, apically borne and for the most part forcibly ejected from their stalks at maturity. Key to Families of Entomophthorales Endozoic parasites (lusecta, Arachnoidea) . 1. Entomophthoraceae. Endophytic or saprophytic 2. Basidiobolaceae, p. 107. Basidiobolaceae This family is characterized chiefly by its habitat. Septa are numerous in the vegetative mycelium. Key to Genera of Basidiobolaceae Intracellular parasites, the mycelium greatly reduced 1. Completoria, j). 108. Saprophytes, or parasites on higher fungi, the mycelium well developed. Conidia produced directly from an un- swoUen conidiophore. Parasites on higher fungi 2. Conidiobolus. Conidia cut off from the ajx^x of a swelling of the conidiophore. Saprophytic... 3. Basidiobolus. 108 THE FUNGI WHICH CAUSE PLANT DISEASE With the exception of the one species given below these are not parasitic on higher plants. Completoria complens Lohde is parasitic upon fern prothallia.^^° Vegetative body compact, of oval or curved branches in a single host cell, extending to other cells by slender tubes. 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Chron. 1875. 88 Smith, W. G., Quar. Jour. Mic. Sc. 15: 1875. 87 Smith, W. G., Diseases of Crops, 1884. 88 Jones, L. R., Sc. 29: 271, 1909. 83 Clinton, G. P., Sc. 33: 746, 1911. "> Clinton, G. P., Ct. R. 362, 1904; also R. 304, 1905. " Whetzel, H. H., Sc. 31: 790, 1910. " Osterwalde, A., C. Bak. 15: 434, 1906. " Bubak, Fr., Zeit. 20: 257, 1910. BlBLlOGRArilV OF PHVCOMVCETES HI ^^de Bary, A., Bot. Zeit. 587, 1881. " Colenuui, L. C, :Mycol. Bull. 2: Dcpt. Agiic. Mysore State, 1910. ™ INIaubUinc, L'Agr. Prat. d. Pays Cliauds 79: 315, 1909. "' Kidley, II. X., Agr. B. Straits tt Fed. Malcy Sts. 10: 70, 1911. " Petch, T., Circ. and Agr. J. Pvuy. Bot. Gard. Ceylon 5: 143, 1910. " Gandary, G., Mem. Y. Rev. See. Cient "Antonio Alzate" 23: 293, 1909. «o Meded, Lands. Plant. Batavia 15: 1896. «' Butler, E. J., Kept. Agr. Research Inst. Pusa 10: 45, 1909-1910. »- Patterson, F. and Charles V. K., B. P. I. 171: 1910. 8' Kawakamia, a new genus belonging to Peronosporacea; on Cyperus tcgetiformis. With a postscript by Dr. Kingo Miyabe, 1904. s-" Butler, E. J., Mem. Dept. Agric. India, 2: No. 1, 1907. «5 Cugini, G. and Traverso, G. B., Staz. sperim. Agr. Ital. 35: 46, 1903. «8 Peglion, C. Bale. 28: 580, 1910. 8^ Berkeley, J., Hort. Soc. Lond. 6: 289, 1851. »8 Dept. Agr. R. 96, 1886. 83 Appel & Richm, Ber d. Kais. Biol Ans. f. L. u. F. Heft, 8, 1908. »° Stewart, F. C, X. Y. (Geneva) B. 32S: 352. " Waite, M. B., Journ. Myc. 7: 105, 1902. 92 Miyabe, K., Trans. Sappora Acad. Sci. 1: 1909. " Davis, J. J., Science, 31: 752, 1910. " Clinton, G. P., Ct. R. 336: 1904, 1905. 95 Rostewzew, Ann. Inst. Agron. Moscow, 0: 47 and Flora 92: 405, 1903. 9« Clinton, G. P., Ct. R. 23: 277, 1899. 9' Hume, H. H., Fla. R. 30, 1900. »« Orton & Garrison, S. C. B. 116: 7, 1905. »9 Halsted, B. D., Bot. Gaz. 1/,: 149, 1889. lo" Farlow, W. G., Bot. Gaz. 14: 187, 1889. '«! Selby, A. D., Bot. Gaz. 27: 67, 1909. i«2 Stewart, F. C, X. Y. (Geneva) B. 110: 158, 1897. w' Arthur, J. C, X. Y. (Geneva) R. /,: 253, 1885. 1" Halsted, B. D., X. J. B. 70. ■"^ Whetzel, H. H., N. Y. (Cornell) B. 21S: 1904. io« Taylor, T. R., D. Agr. 193, 1S72. i»'Trelease, Wm., Trans. Wis. Acad. Sc. G: 7, 1881-1884. i°8 Wis. R. 16: 34, 1883. '"9 Shipley, A., B. 19: Miss. Kcw. 1887. "" Stewart, F. C, French, G. T., & Wilson, T. K., B. X. Y. (Geneva) 305: 394, 1908. "' Rostrup, Zeit. 2: 1, 1892. 112 THE FUNGI WHICH CAUSE PLANT DISEASE 1= Magnus, P., Hedw. 149, 1892. 1' Massee, G., Jour. Linn. Soc. Bot. 2^: 48, 1887. 1" Barrett, O. W., R. Porto Rico 398, 1904. 1' Raciborski, M., Ber. d. Deut. Bot. Ges. 15: 475, 1897. i« Spegazzini, C., Rev. Argent. Hist. Nat. 1: 36, 1891. " Magnus, P., Ber. d. Deut. Bot. Ges. 28: 250, 1910. 18 Taplin, W. H., Amer. Florist 21: 587. 1' C. R. Acad. Sci. Paris, 136: 472, 1906. 20 Blakeslee, A. F., Proc. Acad. Art. & Sci. ^0: 1904. 21 Halsted, B. D., Amer. Flor. 13: 117. " Stewart, F. C, N. Y. (Geneva) B. 328: 342. " Halsted, B. D., N. J. B. 76: 1890. " Orton, W. A., Sc. 29: 916, 1909. " Kirk, T. W., N. Zeal. D. Agr. R. 77: 1909. 2s Swingle, D. B., B. P. I. 37: 1903. " Kew Bull. 871, 1897. 28 Rept. Mic. Vio., N. S. Wales, 1909. 29 Thaxter, R., Rhodora 99: 1903. 30 Atkinson, G. F., N. Y. (Cornell) B. 9I^: 252: 1895, also Bot. Gaz. 19: 47, 1894. 31 Gussow, Ottawa B. 63, 1909. '2 Trow, A. H., Ann. Bot. 18: 541, 1904. " Idem, 15: 269, 1901. " Rosenberg, 0., Bihand till K. Svens Vet. Akad. Handl. 28: 10, 1903. 35 Gruber E., Ber. d. Deut. Bot. Gaz. 19: 51, 1901. 3« Edgerton, C. W., La. B. 126: 1911. 3^ Smith, E. G., Sc. 30: 211, 1909. 38 McCallum, W. B., Ariz. R. 583, 1909. 39 Halsted, B. D., N. J. R. 1893, 393. ^0 Stevens, F. L., Bot. Gaz. 38: 300, 1904. " Bubak, Fr., C. B. 8: 817, 1902. « Magnus, P., C. Bak. 9: 895, 1902. " Farlow, W. G., Bus. Inst. 1: 415, 1871. " Scribner, F. L., D. Agr. R. 96, 1886 ond 88, 1887. « Stewart, F. C., Eustace, H. J. & Sirrine, F. A., N. Y. (Geneva) B. 2U: 1903. « Morse, W. J., Me. B. 169: 1909. " Jones, L. R., Vt. B. 72: 1899. *8 Stewart, F. C., Eustace, H. J. and Sirrine, F. A., N. Y. (Geneva) B. 26^: 1904. 1^9 Farlow, W. G. B. Bussey, Inst. 415, 1876. ASCOMYCETES (p. 64) 2. 7. 19. 26, 46. 62. 63. 62 The distinguishing mark of this group is the ascus. This in its typical form is shown in Fig. 73, as a long, slender or club-shaped sac in which the spores are borne. The number of spores in the ascus is usually definite and is commonly of the series, 1, 2, 4, 8, 16, 32, 64, etc., the most common number being 8. The spores vary in size, color, shape, markings and septation. The asci in most genera are arranged in a definite group, a layer, con- stituting the hymenium which may be either concave, convex, or flat. Between the asci in the hymenium are often found slender hyphal threads of various form, the paraphyses, Fig. 73. The hymenium may be borne in or upon i\ firm substratum of woven threads, the stroma, or upon a very tenuous substratum, the subicu - lum, or without any definite subascal structure. The stromata vary widely in character, size, tex- ture, color, surface, form, etc. The mycelium is usually abundant, branched and septate, the septation readily distinguishing this group from the Phycomycetes. In many species the mycelium weaves together into a false parenchyma and constitutes relatively large pj^, 73._port spore-bearing structures. Fig. 74. The ascigerous organ, ascocarp, or ascoma, if saucer-shaped and open is an apothecium, Fig. 92; if closed a perithecium, Fig. 144. In other cases, the ascigerous layer covers the exterior surface. Fig. 74. On the boundary lines between the Ascomycetes and other groups are fungi which do not present the typical Ascomycete picture but which are regarded as probably belonging to the group, i. e., transition forms between this and other groups. Among such are 113 ion of a hymenium showinK asci and paraphyses. Af- ter Chamberlain. 114 THE FUNGI WHICH CAUSE PLANT DISEASE forms in which the asci are without either stroma or covering, (Protodiscales, p. 125); others in which the asci are not even in groups but are scattered irregularly throughout the ascocarp (Aspergillales, p. 164); and still others with the asci neither in regular groups nor covered (Protoascomycetes, p. 119). One further deviation from the typical form occurs in the Hemiascomy- FiLi. 74. — The large ascocarp of the murel. After Freeman. cetes which possess a sporangium-like structure resembling that of the typical Zygomycete; but a mycelium like that of the typical Ascomycetes. This is by many regarded as the transition form bridging the gap between and indicating the kinship of these two groups; a view strongly supported by the existence of very similar sexual processes in the two groups. Besides the ascus the Ascomycetes possess many other kinds of THE Frxr.i wiimi cause plant disease 115 reproductive struetures in the form of conidia. These may be borne singly or in rows on simple or branched conidiophores. The conidiophores may be single or variously grouped in columns or layers. Figs. 352, 378, 382. In some instances they are very .an err. Fig. 75. — Sphserotheca castagnei. Fertilization and de- velopment of the perithecium. Og= oogonium, an = antheridium, st= stalk-cell. 6 as the aseogonium derived from the oogonium. After Harper. short, innate; again they are long, loose or fioccose. They may emerge through stomata singly or in tufts or they may form sporo- genous cushions below the epidermis or again they may be borne inside of a hollow structure, the pycnidium, which covers them. Chlamydospores are also found. One or several distinct types of sporification may belong to one species of Ascomycete. These dif- ferent forms of spores may appear simultaneously on the same myce- lium or the}' may follow in definite succession regulated by the changes in environment, or again one or more of the spore forms belonging to the life history of the fun- gus may be omitted for long intervals to appear only as the result of stimuli of which little is yet known. The conidia and chhimydospores are asexual spores. Sexuality A. u 'n/ Fiu. 76. — Boudiera. Six sets of sexual organs. After Claussen. 116 THE FUNGI WHICH CAUSE PLANT DISEASE / A.n 's/^; V' '7^ hLh(K% in the great majority of Ascomy- cetes has not been investigated; but in some species fertilization is known to occur; in many species, at least in form similar to that shown by the Phycomycetes, it is absent, probably having been lost by degeneration or else very much modified. In some of the Discomycetes there is one or more carpogonia and fertilization is through a tri- chogyne by spermatia; a mode often met among the lichens. InPyronema,^Fig. 78, the carpogonium is multi-nucleate and it is fertilized by a multi-nucleate antheridium through a trichogyne. Fu- T<^ \ / -^ Fig. 77. — Later stage showing asci and ascophores. After Clausscn. ase asc E Fig. 78. — Pyronema eonfluen.s. A. the .sex organs, og = oogonium, t= trichogyne. B. fertilization stage in section through young apothecium, asc=asci, asf = as- cogenous filament. After Harper. si on of nuclei is probably in pairs as in Albugo bliti of the Phycomy- cetes. In Boudiera '" a very similar relation is found. Figs. 76, 77. In some Perisporiales ^ an uninucleate oogonium is fertilized by an uninucleate antheridium. Fig. 75. THE FUNGI WHICH CAUSE PLANT DISEASE 117 The oogonium after fertilization gives rise to a more or less complicated system of ascogenous hyphae, very simple in the Erysiphaceae, very complex in some Discomycetes, which produces the asci. The sterile parts of the ascocarp, the paraphyses and enveloping structures, arise from parts below the oogonium and antheridium. The very young ascus usually receives two nuclei from the parent strand of the ascogenous hypha. These nuclei unite giving the ?-?>^' 'A'?j- >^ar ^'^^'^-^^^ spreading the fungus during the summer though they have not yet actually been observed to germinate or to cause infection. Apothecia radiatcly arranged on the stroma which is about 0.5-1.5 cm. across; asci 120-130 X 9-10 m; spores large, 65-80 x 1.5-3 m; paraphyses numerous, in- curved or hooked. Conidia ( = M e 1 a s m i a acerina Lev.) preceding the asci, producing numerous small, hyaline, l-ccUed spores in an extended hy- menial layer. On various species of Fig. maple, apparently consist- ing of races since in different localities the host differs without a crossing over of the fungus. R. punctatum (Pers.) Fr. also occurs on maple, especially Acer pseudoplantanus. It may be distinguished from the preceding by its small, speck-like stromata. R. salicinum (Pers.) Fr. is found on willow in Europe and America. It is quite similar in external appearance to R. acerina except for the smaller average size of the spots. R. symmetricum Mull, is another willow inhabiting species. The apothecia are amphigenous and are said to mature in autumn on the still live leaves. Other species are common especially on various Ericaceae and Coniferse in Europe and America. 113. — R. acerinum. F, conidial layer; E, ascus and paraphyses. After Tulasne. Hysteriales (p. 124) Small species with elongated, black, covered apothecia which open by a long narrow slit exposing the hymenium ; asci 8-spored ; spores usually long and slender. Some few are leaf parasites but most are wood saprophytes. Pycnidia are found in some species. The order serves as a bridge between the Discomycetes and the Pyrenomycetes. About four hundred species. 160 THE FUNGI WHICH CAUSE PLANT DISEASE Key to Families of Hysteriales Ascocarps immersed; walls of the ascocarps connate with the membranous cover- ing 1. Hypodermataceae, p, 160. Ascocarps at first immersed, erumpent, walls free Walls membranous or coriaceous, black . 2. Dichaenaceae, p. 162. Walls thick, almost corky, gray or black 3. Ostropaceae. Ascocarps from the first free Walls carbonous, black; shield-shaped, round, oval or more commonly linear 4. Hysteriaceae, p. 163. Walls membranous or horny, brown, ascocarps vertical, clavate 5. Acrospermaceae. The third and fifth families contain no pathogens. Hypodermataceae Ascocarp flattened, rounded or elongate, rarely branched, united to the substratum; opening by a slit; asci 4 to 8-spored; paraphyses apically branched, the branches forming an epi- thecium, or hooked or crimped. About fifty species, chiefly saprophytes. Key to Genera of Hypodermataceae Spores elongate, rather broad Spores 1-celled or l^y cross walls 2 to many-celled Spores 1-celled Asci 8-sporcd, spores spindle-form Spores hyaline 1. Henriquesia, Spores brown 2. Farlowiella. Asci 4-spored, spores hyaline 3. Hypodennella, p. 161. Spores 2-celled, h3^aline Apothecium black 4. Hypoderma, p. 161. Apothecium red 5. Angelinia. THE FUNGI WHICH CAUSE PLANT DISEASE 161 Spores 4 to many-celled, spindle-form Spores 4-celled, mostly hyaline G. Gloniella. Spores 4 to many-celled, brown 7. Rhytidhysterium. Spores niuriform, hyaline 8. Hysteropsis, p. 161. Spores filiform, 1-celled 9. Lophodermium, p. 161. Of these genera only four are important here. Hypodermella Tubeuf (p. 160) This differs from the next genus in its pyriform unicellular spores; asci 4-spored. Two species, both European and economic. H. larius Tub. affects larch needles in Europe. ^^ H. sulcigena Link is on pine needles. Hypoderma De CandoUe (p. 160) Apothecia oblong, opening through a thin black cover by a long fissure; asci 8-spored; spores cylindrical or fusiform, 2-celled at maturity; paraphyses hooked at the end. H. desmazieri Duby,^^^ on pine needles in America and Eu- rope. Amphigenous; asci broadly" clavate, sessile; spores hyaline, linear-elliptic, obtuse and 2-rowed. H. laricis, H. strobicola, H. pinicola, produce premature leaf fall in various conifers. Hysteropsis Rehm Asci clavate, 8-spored; spores hyaline, muriform; paraphyses branched, forming an epithecium. H. brasiliensis occurs on cacao trees. Lophodermium Chevall Spores long, thread-like, continuous; conidiospores in pycnidia. L. pinastri (Schr.) Chev. occurs in Europe ^~ and America on Pinus sylvestris especially on young plants causing the leaves to fall. The first year pycnidia only are formed, the asci not ap- pearing until the second year.^^ 162 THE FUNGI WHICH CAUSE PLANT DISEASE Ascocarps scattered on the leaf, shining black, up to 1 mm. long; asci clavate, 8-spored; spores nearly as long as the ascus, 90-120 X 1.5 /i. Conidia cyhndric, hyaUne, continuous, 6-8 x 1 ;u. L. brachysporum Rost. Perithecia epiphyllous; asci cylindric, short- stalked, apex rounded, 120 x 20-25 fi, 8- spored; paraphyses bacillar, apex curved; spores oblong, 1-rowed, hyaline, 28-30 x 9-10 yu. It is common on pine leaves. ^^^ Several other species are parasitic upon various conifers, among them: L. macrospo- rium (Hart.) Rehm, on spruce leaves, in Europe and America; L. nervisequum (D. C.) Rehm, on fir leaves, a very destructive European species; the pycnidial stage is Septoria pini Fuckel; L. juniperinum (Fr.) d Not, on juniper leaves and twigs in Europe and America; L. gilvum Rost., on pines; L. abietis Rost., on spruce leaves; L. laricinum Duby, on larch. The last four species are European. J Fig. 114. — L. pinastri. H^ habit sketch; J, ascus and paraphj-- ses. After Rehm. Dichaenaceae (p. 160) This family contains the single genus Dichaena. Dichaena Fries Apothecia grouped in rounded spots; at ^m\i' first sunken, then erumpent, rounded or elon- mrih\Mk gate, dark brown; asci irregularly pyriform, 4 ^esg,^t^}]l'-^\:])^^^^ to 8-spored; spores ellipsoidal, at first 1-celled, ^^^^fesn^^y^ at maturity multicellular; paraphyses filiform, ^iq. ii5.— Hysterium Some seven species are found upon various macrosporum. Af- ^ ^ ter Hartig. trees. D. quercina Fr. causes rough black patches on bark of young oaks in Europe and America; D. faginea Fr., a similar effect on beech. THE FUNGI WHICH CAUSE PLANT DISEASE 163 Hysteriaceae (p. 160) Ascocarps free, seated upon the substratum, elongate or linear, straight, curved or even branched, disk-form, boat-shaped or band-like, black; asci usually 8-spored; paraphyses fila- mentous, often forming an epithecium. About fourteen genera and some two hundred fifty species, many but poorly known. Several genera contain plant patho- ^^°- n^- — D. quer- , . ., , 1-, r • • cina. Ascus and gens, but they are not often of economic mi- paraphyses. After portance. ^"^^• Key to Genera of Hysteriaceae Ascoma linear, flattened, broadly sessile Spores ellipsoid or spindle-shaped, many- celled Spores 1-celled, 16 in each ascus 1. Cyclostomella. Spores 2-celled, sometimes 4-celled, ellipsoid or elongate Spores hj'aline Asci 8-spored, spores 2 to 4-celled Paraphyses scarcely branched. . 2. Aulographum. Paraphyses forming an epithe- cium 3. Glonium. Asci many-spored, spores 2-celled . 4. Hariotia. Spores colored, 2-celled; leaf infect- ing fungi Paraphyses present Ascoma seated on a cottony stroma 5. Lembosia. Ascoma radial, on a circular stroma Spores 2-celled, 8 in each ascus 6. Parmularia. Paraphyses absent, stroma irreg- ularly circular 7. Hysterostomella. Spores 4 to 8-celled, elongate or spindle- form Spores hyaline, spindle-form, 4- celled 8. Hysteroglonium. 164 THE FUNGI WHICH CAUSE PLANT DISEASE Spores brown, elongate, 4 to 8-cellecl 9. Hysterium, Spores elongate, muriform 10. Hysterographium, p. 164. Ascoma boat or band-shaped, not sessile Spores spindle-formed, brown, many- celled Spores 4 to 8-celled; asci 8-spored. 11. Mytilidium. Spores many-celled; asci 4-spored. 12. Ostreion. Spores filamentose, hyaline or yellow 13. Lophium. Ascoma stellate 14. Actidium. Hysterographium Corda Asci clavate, 8-spored; spores muriform, dark colored when mature; paraphyses branched forming an epithecium. About seventy species. H. fraxini (Pers.) de Not. occurs on Oleaceae, particularly on Fig. 1 17. — H. fraxini. Ascus and paraphyses. After Rehm. Fig. 118. — Gymnoascus, sexual organs. After Dale. the ash, perhaps only as a saprophyte. It is found both in Europe and America. Aspergillales (p. 124) The Aspergillales are clearly distinguished from the other Ascomycetes by the possession of a closed ascocarp in which the asci are not collected in a hymenium but are irregularly scattered. The forms with the least developed peridium are evidently related THE FUNGI WHICH CAUSE PLANT DISEASE 165 to the Endomycetacesc; the forms with a more highly developed pcridium, to the Pyrenomycetes, particularly to the Perisporiales. Conidial forms are usually present, indeed in many cases they preponderate almost to the entire exclusion of the ascigerous form which may be seen only under very exceptional conditions. Sexual reproduction has been demonstrated in several families. In the Gymnoascacese (Dale ^^ and Eidam ^^) there are usually two twisted branches (Fig. 118) which conjugate. These branches are multinucleate at the time of fusion. The ascogonium de- velops from this fertilization much as is described on pages 116- 117. In the Aspergillacea? similar sexual organs are formed but parthenogenesis or a much reduced form of fertilization is often met. In all, the species number two hundred fifty or more. Key to Families of Aspergillales Pcridium made up of loose floccose hyphse . 1 . Gymnoascaceae. Pcridium compact, closed Ascocarps mostly small, not subterranean Ascocarps mostly sessile without stroma; peridia remaining closed. . 2. Aspergillacese, p. 166. Ascocarps mostly stalked ; peridia open- ing at maturity by lobes, or ir- regularly 3. Onygenaceae. Ascocarps sessile, the spores issue in columnar masses from the goblet- shaped peridia 4. Trichocomaceae. Ascocarps sessile on a small stroma. . . 5. Myriangiaceae, p. 170. Ascocarps mostly enlarged, tuberous, sub- terranean. Peridium clearly distinct from the walls of the ascocarp ; spore masses powdery at maturity 6. Elaphomycetaceae. Peridium not clearly limited, continu- ous with the walls of the ascocarp; spore masses never powder)' 7. Terfeziaceae. Of thpse the second and fifth families only contain pathogens. The Gymnoascacese of five genera and some fifteen species are found on manure, and other organic matter. The third and fourth 166 THE FUNGI WHICH CAUSE PLANT DISEASE families are monogeneric; the third on hoofs, horn, etc.; the sixth is subterranean and the Terfeziacese more or less subter- ranean. Aspergillaceae (p. 165) The aseocarp, in many forms but rarely seen, is a small spherical or tuber-shaped body, usually indehiscent, rarely opening by a pore. The spherical or pyriform asci bear from 2 to 8 spores which may be from 1 to many-celled. The aseocarp is in some genera provided with appendages which strongly resemble these of the Erysiphacese (Microascus). Conidia are produced in great abundance. In Aspergillus and Penicillium fertilization is said by some observers to be accomplished by conjugation of a straight oogo- nium with a spirally coiled antheridium, this act resulting in an ascogenous hypha. Recent work of Dale '° (see also Fraser and Chambers ^^) denies such fusion in one species of Aspergillus which she studied, though sexual organs were often present, and predicates a reduced form of sexuality consisting of fusion of the nuclei of the ascogonium with each other. Key to Genera of Aspergillaceae Spores l-celled Perithecium flask-shaped, beaked or papil- late 1. Microascus. Perithecium not beaked Perithecium with hair-like appendages ; peridium compact, mostly dark colored Appendages straight hairs or forming a hairy felt 2. Cephalotheca. Appendages apically coiled hairs. ... 3. Magnusia. Perithecium unappendaged ; peridium membranous or fleshy Conidia borne directly on the myce- lium Chlamj^dospores borne in chains. . 4. Thielavia, p. 167. Chlamydospores borne singly 5. Rostrella, p. 168. THE FUNGI WHICH CAUSE PLANT DISEASE 167 Conidia borne on distinct conidio- phores Conidia borne singly; conidio- phores branching at right angles 6. Aphanoascus. Conidia borne in chains Conidiophores sinij^Ic, aggre- gated into bundles 7. EmericeUa. Conidiophores enlarged apically bearing numerous sterig- mata Sterigmata simple 8. Aspergillus, p. 168. St smooth. The invaded leaf tissue is colored by the mycelium which bears a reddish oil. Nu- merous perithecia are immersed in the diseased area and, opening to the surface, extrude spores which seem incapable of in- fecting. During winter the stroma darkens, turns hard and produces the perithecia and ascospores. Ascogonium and trichogyne-like organs have been described.^'*'* P. ochraceum (Wahl.) Sacc. occurs on Prunus padus. Fig. 148.— p. rubrum. D, asci; E, conidia. After Fisch. Valsonectria Spegazzini (p. 198) Stroma thin, cushion-shaped, under the bark of the host; peri- thecia similar to those of Valsa, sunken in the stroma, the beak erumpent, red; asci cylindric, 8- spored; spores 2-celled, hyaline or light brown. A genus of but three species which differ from Valsa chiefly in their red color. V. parasitica (Murr.) Rehm.^^^' ^^^' Pustules numerous, erumpent, at first yellow, changing to brown at maturity; perithecia usually ten to twenty in number, closely clustered, flask-shaped, deeply embedded in the stroma in the inner bark, scarcely visible to the unaided eye; necks long, slender, curved, with thick black walls and rather prominent ostiola; asci oblong- clavate, 45-50 x 9 m, 8-spored; spores usually biseriate, hyaline, oblong, rounded at the ends, often slightly constricted, unisep- tate, 9-10 X 4-5 /x. Summer spores very minute, 1 x 2-3 ix, pale- Fig. 149. — Showing a pycnidium of Valsonectria and the manner iu which the spores issue from it. After Murrill. THE FUNGI WHICH CAUSE PLANT DISEASE 209 yellowish, cylindrical, slightly curved, discharged in twisted threads as in Cytospora. This fungus, originally described as Diaporthe parasitica, is a serious parasite on the chestnut. The mycelium grows through the inner bark in all directions from the initial wound at which in- fection occurred, eventually girdling the part. The wood is also affected. The perithecia appear in abundance upon or in cracks of the bark, extruding their spores in greenish to yellow threads. Hypocrea Fries (p. 199) Stroma subglobose to patellate, fleshy or subfleshy; perithecia entirely immersed, subglobose to ovate, the necks slightly pro- truding; asci cylindric, originally 8-spored, spores breaking each into two so that the asci at maturity contain sixteen hyaline spores. About one hundred ten species. H. ceretriformis Berk, occurs on the bamboo in Tonkin; H. sacchari on sugar cane. Balansia Spegazzini (p. 199)^^^ Sclerotium composite, formed of the affected parts of the host embedded in a well developed mass of fungous tissue; stroma arising from the sclerotium, stipi- tate and capitate or sessile, pul- vinate, obovate, discoid, or sepa- rated from the sclerotium as soon as the latter is mature, sur- face slightly papillate from the projecting ostiola of the im- mersed scattered perithecia; asci 8-spored; paraphyses none. Co- nidia, when known, an Ephelis and preceding the stroma. B. hypoxylon (Pk.) Atk. oc- curs on various grasses, chiefly in the southern United States. B. claviceps Speg. infests Setaria and Pennisetum in tropical lands. The^ remaining species, chiefly of warm regions, are mostly grass inhabiting. Fig. 150. — B. hypoxylon, section of pscudosclcrotium and one stroma showing pi'rithecia, stom, leaf ele- ments and an ascus. After Atkinson. 210 THE FUNGI WHICH CAUSE PLANT DISEASE Dothichloe Atkinson (p. 199) ^^^ Stroma thin, hard when dry, black, especially the outer portion, lighter within, effuse, pulvinate, disciform or armilla-form, partly or entirely surrounding the host; perithecia crowded, confluent with the stroma, but the thin walls of distinctive structure, im- mersed, the apex projecting; asci cylindric, 8-spored; spores fili- form, septate at maturity, and eventually separating at the septa into short seg- ments. Like the preceding genus, both species D. atramentosa (B. & C.) Atk. and D. aristidae Atk. are grass inhabitors of warm regions of the United States. The former is the commoner species with a wider range of hosts. Epichloe (Fries) Tul. (p. 199) Stroma effused, subfleshy, at first pale, becoming bright orange, sheathing the host; perithecia immersed or with the ostiola protruding; asci cylindric, 8- spored; spores filiform, many-celled. Of some nine species only one is important. E. tjrphina (Pers.) Tul. Stroma ef- fused, at first pale, becoming bright orange, forming sheaths 2-5 cm. long Fig. 151.— Epichloe. A, habit around stems of various grasses, often L^cS^b^afcX'A as°co" destroying the inflorescence; perithecia spore. After Winter, Bre- thickh'^ Scattered, partially or entirely im- feld and Lindau. i • , i ^ r, i mersed m the stroma, soit, membranous, concolorous with the stroma, the ostiole rather prominent; asci very long; spores almost as long as the ascus, closely fasciculate, multiseptate, about 2 fx in diameter; conidia elliptic, hyaline, 4-5 X 3 ju, preceding the perithecia on the stroma. Many grasses are affected, often to serious extent. The mycelium shows first as a yellowish cobwebby growth surrounding the leaf sheath and soon develops a conidial stroma. Later the stroma THE FUNGI WHICH CAUSE PLANT DISEASE 211 turns to orange-color and the perithecia appear, forming a layer. Echinodothis Atkinson (p. 199) "^ Stromata subfleshy or corky, light-colored, pulvinate to sub- globose or irregular in form, often constricted at the base, some- times entirely surrounding the host, consisting of several layers of different consistency; perithecia superficial, scattered, subcylindric, sessile, giving an echinulate appearance to the stroma; asci cylin- dric, 8-spored; spores linear, septate, at length separating at the septa into short segments. Two species, parasitic on grasses in the warmer parts of the western hemisphere. E. tuberiformis (Berk. & Rav.) Atk.^^e Stromata subglobose, 1 cm. or more in diameter, entire, lobed, or divided, seated upon the reed or upon the leaf-sheath and fas- tened by a whitish mycelium consisting of radiating threads which are sometimes tinged yellowish-brown; substance leathery or corky, consisting of three layers, an inner layer white to pinkish, an inter- mediate layer light ochraceous and an outer layer cinnamon; stroma externally dark brownish becoming black; conidiophores needle-shaped; conidia ovoid to fusoid, 3^ x 7-10 ix; perithecia entirely superficial in small clusters or evenly distributed over the exposed surface of the stroma, subconic in form, giving the whole stroma a spiny appearance, clothed except the apex with a dense covering of minute ^threads which are at first whitish, be- coming cinnamon colored, the naked apex becoming black, about 0.3 X 1 mm. ; asci cylindric, with a swelling at the apex, very large, 475-750 x 14-20 (j.; spores nearly as long as the ascus, hyaline or slightly yellowish, many-septate, the joints 15 x 4-5 /x. On Arundinaria in the Southern States. Asciculosporium take Miy.'^^ forms witches' brooms on bamboo in Japan. It is closely related to Dusiella and Epichloe. Claviceps Tulasne (p. 199) Sclerotium formed within the hypertrophied tissues of the ovary of the host, succeeding the conidial stage which is a Sphacelia; stroma erect, with a long sterile base and a fertile, 212 THE FUNGI WHICH CAUSE PLANT DISEASE usually knot-like head; perithecia closely scattered, sunken in the stroma with only the ostiole protruding, flask-shaped, the walls scarcely distinguishable from the stroma; asci cylindric, Fig. 152. — C. purpurea. D, Sphacclia stage; E, germinated sclerotia; G, sec- tion of stroma; H, section of a perithecium; J, ascus with spores. After Tulasne. 8-spored; spores hyaline, continuous. Some twelve or fifteen species are recorded all affecting the ovaries of the Graminese. C. purpurea (Fr.) Tul.^^^ Sclerotium elongate, more or less curved, and resembling a much enlarged grain, after a period of rest producing few or many, clustered or scattered stromata which are 0.5-1.5 cm, high; spore THE FUNGI WHICH CAUSE PLANT DISEASE 213 60-70 fi. long. Conidia ( = Sphacelia segetum) produced on the grain before the sclerotium is formed, conidiophores short, cylin- dric, arranged in a compact palisade, bearing small, oval, hyaline, 1-celled conidia. Hosts, rye, wheat, oats and numerous other grasses. Infection of the ovary at blooming time is followed by complete possession and consumption of the ovarial tissue by the mycelium, and by considerable development of stroma beyond the ovary. On the external much-folded part of this stroma, particularly at its distal end, are borne layers of conidiophores and numerous conidia and a sweet fluid is exuded. The conidia, carried by in- sects, spread summer infection. Lator the stroma, losing a large part of the distal region, rounds off to a definite sclerotium, smooth, firm, blue to black in color, and several times larger than the normal grain of the host plant. After a period of rest, usually lasting till the following season, the sclerotium gives rise to several stalked, capitate, perithecial stromata. The perithecia are arranged around peripherally, the ostioles protruding and giving the head a rough appearance. The sclerotium constitutes the ergot of pharmacy and contains a powerful alkaloid capable of causing animal disease if eaten. This species appears to be differentiated into a number of biologic races. ^'*^ C. microcephala (Wal.) Tul. infects numerous grasses both in Europe and America, being especially destructive to blue grass. Two species C. paspali S. & H. and C. rolfsii S. & H. have been reported on Paspalum.^^^ Ustilaginoidea Brefeld (p. 199) 150 Sclerotium formed in the grain of the host, resembling super- ficially a smut sorus, in the center composed of closely interwoven hyphae, externally the hyphse are parallel, radiating towards the periphery and bearing echinulate, globose, greenish conidia; stroma with a long sterile stem and a fertile head; perithecia immersed in the stroma as in Claviceps; asci and spores also as in Claviceps. Two species are known, one on Setaria which produces an ascigerous stage, the other on rice, the ascigerous stage of which 214 THE FUNGI WHICH CAUSE PLANT DISEASE is not known but which is placed in this genus on account of the similarity of its conidial stage with that of the other species. U. virens (Cke.) Tak. Ascigerous stage unknown, sclerotia spher- ical, about 5 mm. in diameter; conidia spherical, at first smooth- walled, hyaline, at maturity echinulate and olive green, 4-6 fx. The short thick walled hyphse of the interior of the sclerotium are closely in- T? i-o"^!--^ ..I- terwoven to a false tissue. Fig. 1o3. — U. virens; a, spores germinated m . ' water; b, germinated in bouillon. After toWard the periphery they become parallel and are di- rected radially. Here a yellow layer is produced and spores are formed laterally on the hyphae. When mature the spores are in mass dark olive-green and form an outer green layer on the sclerotium. The spores germinate in water, producing a vegeta- tive mycelium which bears secondary spores and somewhat re- sembles the mycelium of the Ustilaginales.^^^ Successful inocula- tions have not been made. Ustilaginoidella Essed (p. 199) This is a genus erected by Essed ^°- to receive the species U. musaeperda, which he regards as the cause of the "Panama disease" of bananas, at least as it occurs in Suriname. Sclerotia similar to those of Ustilaginoidea are found; chlamyd- ospores and conidia obtain, among the latter are some of marked Fusarium type; others are in pycnldia. U. oedipigera Essed is also described by Essed ^°^ as the cause of another less important banana disease in Suriname and Colum- bia; a disease accompanied by hypertrophy of the base of the stem and leading to the common name "bigie footoe." This fungus differs from the last in its 1 to 2 to 3-celled conidia. U. graminicola Essed causes a rice disease. ^°^ This species differs but slightly from the two preceding. Chlamydospores smaller, conidia 1 to 5-celled. THE FUNGI WHICH CAUSE PLANT DISEASE 215 LocuHstroraa Patterson & Charles ^^- (p. 199) Stromata upright, sessile, at the nodes of the host, fleshy, soft, green or black, containing conidial chambers in which are pro- duced hyaline filiform conidia and on the outer surface of which are borne Cladosporium-like conidia; perithecia scattered, partly immersed, ostiolate; asci clavate, cylindric, 8-spored; spores fusi- form, 3 to many-septate, olivaceous, biseptate; paraphyses none. There is only one species known. L. bambusae. P. & C.^^^ Stromata 1 cm. long by 2 mm. in diameter; perithecia almost spherical, 125 x 100 m; asci 45-50 x 9-10 n; spores 22 x 4. 5-5 n; primary conidia 14-16 x 0.75-1 n; borne in chambers on basidia, 8 x 0.5 ju; secondary conidia external, 1 to 3-celled, borne on external olivaceous hyphae. It causes a witches' broom of bamboo (Phyllostachys sp.), in China. Infection probably occurs in the terminal node. The fully developed sclerotia-like structures, resembling those of Claviceps, are dark green to black when mature, and consist of a central hyaline sclerotial tissue in which are many round conidial chambers. Perithecia develop from the peripheral layer. Dothidiales (p. 124) There is only one family the Dothidiaceae. Mycelium developed in the substratum, septate, at length form- ing a thick, dense, very dark stroma in which the perithecia are sunken and with which their walls are completely fused, rarely partly free; asci borne from the base of the perithecium; paraphyses present or none. The Dothidiaceffi contain some four hundred species and more than twenty-four genera. They differ from the last order in their firm black sclerotium-like stromata which are usually pale to white within. The perithecia are usually grouped together in great num- bers in the external layer of the stroma, sunken in its undiffer- entiated body. Conidia of various forms are present. 216 THE FUNGI WHICH CAUSE PLANT DISEASE Key to Genera of Dothidiaceae Stromata at first sunken later more or less free Perithecia standing free on the stroma; spores at maturity, 4-celled, dark 1. Montagnellao Perithecia almost completely embedded in the stroma Stromata variable, more or less irreg- ular in outline but never elongate Spores 1-celled Spores hyaline Asci typically borne at the base of the perithecium Asci 8-spored Spores eUipsoid Perithecia few 2. Mazzantia. Perithecia numerous. . 3. Bagnisiella. Spores filiform 4. Ophiodothis. Asci many-spored 5. Myriogenospora. Asci borne laterally at the equator of the perithe- cium, spores ellipsoid. . . 6. Diachora, p. 217. Spores brown 7. Auerswaldia. Spores 2-celled Spores hyaline Spores ovate 8. Plowrightia, p. 217= Spores needle-like 9. Rosenscheldia. Spores colored Cells of the spore similar. ... 10. Roussoella. Cells of the spore dissimilar. . 11. Dothidea, p. 220. Spores several-celled Spores with cross walls only Spores hyaline, 4-celled 12. Darwiniella. Spores colored, multicellular 13. Homostegia. Spores muriform Spores hyaline 14. Curreyella. Spores colored 15. Curreya. Stromata elongate, linear or lanceo- late THE FUNGI WHICH CAUSE PLANT DISEASE 217 Spores hyaline Spores 1-celled 16. Scirrhiella. Spores 2-celled 17. Scirrhia. Spores 4 to 8-celled, fusiform. . . 18. Monographus. Spores colored, multicellular, fusi- form 19. Rhopographus. Stromata sunken, permanently united to the epidermis and substratum Spores 1-celled 20. Phyllachora, p. 220. Spores 2-celled Spores of similar cells 21. Dothidella, p. 221. Spores of dissimilar cells 22. Munkiella. Stromata from the first superficial Stromata encrusted, widely spreading. . . 23. Hyalodothis. Stromata cushion-shaped, limited 24. Schweinitziella. Of these genera only five are of interest as plant pathogens. The majority contain only saprophytes. Diachora Muller (p. 216) The genus is easily recognized by its peculiarity of bearing asci only as an equatorial band instead of on the floor of the perithecia, a char- acter unique among the Pyrenomy- cetes. D. onobrychidis (D. C.) Mull, is reported as causing black spots on leaves of sainfoin and Lathyrus in Europe. Plowrightia Saccardo (p. 216) Stromata formed within the tissues p,^ 154.-0!" onobrychidis. E, co- Of the host plant, erumpcnt, tuber- nidial stage ;F,ascocarp and asci. Y , , , After Muller. cular or cushion-shaped, depressed or elevated, smooth, later frequently wrinkled, white within; asci cylindric, 8-spored; spores ovate, 2-celled, hyaline or light green; conidial forms Cladosporium, Dematium, etc. 218 THE FUNGI WHICH CAUSE PLANT DISEASE Some twenty species are known. They are distinguished from Dothidia by the hyaline spores. Fig. 155. — P. morbosa. b, magnified section of a knot showing the perithecia; c, conidiophores and conidia; d, section of a peri- thecium showing numerous asci, one of which is shown more highly magnified at e; f. several of the two-celled ascospores germinating in water. After Longyear. P. morbosa (Schw.) Sacc^^^'^^'' ''^^ Stromata elongate, cushion-shaped, rarely tubercular, up to 2 or THE FUNGI WHICH CAUSE PLANT DISEASE 219 m ■'"S Fig. 156. — P. morbosa; host showing opportunity for lodgement for spores in a crotch. After Lodeman. 3 dm. long; perithecia scattered, often entirely suppressed; asci about 120/1 long; spores variously arranged in the ascus, 16-20 x 8-10 fi, ovate, the cells usually unequal; paraphyses filiform. Conidia (= Cladosporium sp.) pro- duced upon greenish areas on the young stromata; conidiophores erect, flexuose, septate, simple, 40-60 x 4-5 n; conidia borne singly at the apex of the conidio- phore, obovate, unicellular, light brown, about 6-8 X 2-5 /z. Hosts: Cultivated sour cherry and plum, wild red and yellow plum, Chickasaw plum, choke cherry, wild red cherry and wild black cherry. Found only in America. The mycelium invades the cambium of twigs and from it grows outward into the bark region causing the bark elements to overgrow and the twig to swell slightly dur- ing the first summer. With the renewed growth of the following spring the swelling proceeds rapidly. During May to June the mycelium ruptures the bark which is soon lost and a dense fun- gous pseudoparenchyma is formed. From this the conidiophores appear, forming a velvety growth of olivaceous color. At this period the knot consists largely of a fungous stroma with an ad- mixture of bark elements and even some wood cells. Later in the season conidiophores cease to form and the knot turns to a black hard stroma. Perithecia now become easily visible in this black stroma and in January or later the asci mature. Farlow has described " stylospores " (a form named Hendersonula morbosa by Saccardo the connection of which to P. morbosa is in some doubt) and spermogonia and pycnidia. Humphrey ^^^ from ascospores, in artificial media, raised a pycnidial form which seemed to be distinct from any of these. That the fungus is the actual cause of the black knot was first demonstrated by Farlow ^^^ in 1876, though the fungus was described as early as 1821 by Schweintiz.i^s Lodeman ^""^ considered that infection is favored by cracks existing at crotches of the tree. Fig. 156. 220 THE FUNGI WHICH CAUSE PLANT DISEASE P. ribesia (Pers.) Sacc. is found in Ribes twigs and P. virgultorum (Fr.) Sacc. on birch. Both are European.. P. agaves occurs on the maguey. ^^'^ Dothidea Fries, distinguished from Plowrightia by its colored spores, contains some twenty-five species which occur on twigs of Sambucus, Rosa, Buxus, Betula, juniperus, Quercus and many other woody plants. D. rosae Fries, is common as the supposed cause of a rose tumor. D. noxia Ruhl. causes an oak twig disease in Germany. ^^^ Phyllachora Nitschke (p. 217) Stroma sunken, united to the parenchyma and epidermis of the host leaf, rarely erumpent, encrusted, usually jet-black; peri- thecia sunken in the stroma, rather numerous, with more or less distinct ostioles; asci cylindric, 8-spored; spores ellipsoid or ovate, 1-celled, hyaline or yellowish; paraphyses present. More than two hundred species, largely tropical, are known on a wide range of hosts. All are leaf parasites. P. graminis (Pers.) Fcl. Stromata variable in size and form, causing conspicuous black spots on leaves of the host; perithecia immersed, os- tiolate; asci short-pedicillate, cylindric, 70-80 x 7-8 (x; spores obliquely uniseriate, ovoid, hya- line, 8-12 X 4-5 n; paraphyses filiform. No conidia are known. This fungus occurs on many grasses and After sedges with slight injury to them. P. pomigena (Schw.) Sacc. produces black spots, scarcely ever above 5 mm. in diameter, on apples, especially the Newton Pippin, in the eastern United States. Little is known of the species. P. trifolii (Pers.) Fcl. causes small black spots 1 mm. or less in diameter on clover leaves; asci cylindric; spores uniseriate, oval, hyaline, 8-10 x 5-6 /jl. Conidia ( = Polythrincium trifolii) precede the asci on the stro- FiG. 157. — P. gram- inis. B, stroma in section; C, an ascus and spores. Winter. THE FUNGI WHICH CAUSE PLANT DISEASE 221 mata; conidiophores wavy or zigzag, erect, simple, black, conidia obovate, 1-septate, constricted, pale olivaceous, 20-24 x 9-10 /z. The conidial form is very common on various species of clover in Europe and America while the ascosporic stage is mentioned only by Cooke ^''° and Clevenger.^^^ P. cynodontis (Sace.) Niess. on Cynodon, P. poae (Fcl.) Sacc. on Poa and P. dapazioides (Desm.) Nke. on Box and Rhododendron are European, P. makrospora Zimm. occurs on Durio zibel- linus; P. sorghi v. Hoh. on Sorghum vulgare.^^- Dothidella Spegazzini differs from Phyllachora in having 2-celled hyaline spores, the cells un- , . . „, £.f., . „ Fig. 158.— D. betu- equal m size, ihere are over mty species of lina. Asci and the genus. Epiphyllous, subrotund confluent, winter.^' ^^^^^ convex, grayish-black, on white spots; ostiole granular; asci cylindric, short-stipitate, 60-70 x S n; spores ob- long, ovate oblong, hyaline, 10-15 x 5 /i. D. ulmi Duv.^^° Co- nidia=Septoria ulmi and Piggatia astroidea. On elm in Europe and America. Other species are D. thoracella (Rostr.) Sacc. on Sedum, in Europe, D. betulina (Fries) Sacc. on Betula in Europe and Asia. Sphaeriales (p. 124) Mycelium chiefly confined to the substratum; perithecia vari- able, usually globose, with a more or less elongated ostiole, hairy or smooth, free on the substratum, more or less deeply sunken, or borne on or sunken in a stroma; asci borne basally, variable in size, opening by a pore; spores variable, globose, ovate to elongate or filiform, hyaline or colored; paraphyses usually present; conidial forms various. The stromata may vary from a delicate hyphal weft to a firm crustaceous structure. The pycnidia are mostly carbonous, black and brittle. Conidia of many forms are present and often con- stitute the only truly parasitic form of the fungus; the asci- gerous form developing only after the death of the part of the host involved. 222 THE FUNGI WHICH CAUSE PLANT DISEASE The order is very large, embracing according to Engler & Prantl some eighteen families and over six thousand species. Key to Famiues of Sphaeriales Perithecia free, either without a stroma, partly seated in a loose mass of myce- lium, or sessile above an imperfect stroma Walls of the perithecia thin and mem- branous; asci soon disappearing Perithecia always superficial, with copious tufts of hair at the mouth 1. Chaetomiaceae. Perithecia usually sunken, with only short hairs about the mouth 2. Sordariaceae, p. 224. Walls of the perithecia coriaceous or car- bonous Perithecia either entirely free, or with the base slightly sunken in the substratum or stromatic layer Stroma wanting or only thread-like or tomentose Mouths of the perithecia mostly in the form of short papilla;. ... 3. Sphaeriaceae, p. 225. Mouths of the perithecia more or less elongate, often hair-like. . 4. Ceratostomataceae, Stroma present p. 232. Stromata mostly well developed, indefinite; perithecia in close irregular masses, never flask- like of funnel-like at the apex 5. Cucurbitariaceae, p. 234. Stromata small, sharp-bordered; perithecia in rows or in regu- lar rounded masses, flask- shaped with funnel-shaped mouths 6. Coryneliaceae. Perithecia more or less deeply simken in the substratum at base, free above Mouths of the perithecia circular in outline 7. Amphisphaeriaceae. THE FLNGI WHICH CAUSE PLANT DISEASE 223 Mouths of the perithecia laterally compressed Perithecia without a stroma, and sunken in the substratum, or with a stroma Stromata none; perithecia rarely united above by a black tissue (clypeus) Asci not thickened at the apex, mostly projecting at maturity Walls of the perithecium thin, cori- aceous; mouth mostly short or plane Asci chnging together in fascicles, without paraphyses Asci not fasciculate; with para- physes Walls of the perithecia carbonous or thick coriaceous; spores large, mostly enveloped by gelatine. . Asci usually thickened apically, open- ing by a pore; perithecia usually beaked Perithecia without a clypeus Perithecia with a clypeus Perithecia firmly imbedded in a stroma, the mouths only projecting, or becom- ing free by the breaking away of the outer stromatic layers Stromata fused with the substratum Conidia produced in pycnidia Conidia developed from a flattened surface Stromata formed almost wholly of hard- ened fungal hypha? Spores small, cylindric, 1-celled, mostly curved, hyaline or yel- lowish-brown Spores rather large, 1 to many-celled, hyaline or brown, conidia mostly in cavities in the stroma Spores 1-celled, rarely 2-celled, blackish-brown. Conidia devel- 8. Lophiostomataceae. [p. 235. 9. Mycosphaerellaceae, 10. Pleosporaceee, p. 250. 11. Massariaceae, p. 262. 12. Gnomoniaceae, p. 263. 13. Clypeosphaeriaceae, p. 276. 14. Valsaceae, p. 277. 15. Melanconidaceae, p. 279. 16. Diatrypaceae, p. 281. 17. Melogrammataceae, p. 282. 224 THE FUNGI WHICH CAUSE PLANT DISEASE oped on the upper surface of the young stroma 18. Xylariaceae, p. 284. Families Nos. 1, 6, 7, 8, 17 are saprophytes on plants and animals. Sordariaceae (p. 222) Perithecia superficial or deeply sunken in the substratum, often erumpent at maturity, thin and membranous to coriaceous, slightly transparent to black and opaque; stroma usually absent, if present the perithecia immersed in it with projecting papilliform beaks; asci usually very delicate, cylindric, 8-spored; spores usually dark-colored; paraphyses abundant. A small order, chiefly dung inhabiting. Key to Genera of Sordariacese Spores continuous Without a stroma Neck of the perithecium hairy 1. Sordaria. Neck of the perithecium with black spines 2. Acanthorhynchus, p. 224. With a stroma 3. Hypocopra. Spores 2 or more celled Spores 2-celled Spores hyaline 4. Bovilla. Spores dark-brown 5. Delitschia. Spores 4 to many-celled Stroma absent 6. Sporormia. Stroma present 7. Sporormiella. Spores muriform; stroma present 8. Pleophragmia. Acanthorhynchus Shear ^^^ Perithecia scattered, submembranous, buried, beaked, the beak with non-septate spines; asci opening by an apical pore; paraphyses present, septate; spores continuous, brownish-yellow. There is a single species, A. vaccinii Sh.^^^ Amphigenous: perithecia subglobose to flask-shaped, scarcely erumpent, 120-200 /z in diameter, neck stout, exserted, ^l^-^U the length of the perithecium; spines 50-70 x 8-9 ix; asci subelliptic to somewhat clavate, subsessile, 120-155 x 24-44 /x; spores oblong- THE FUNGI WHICH CAUSE PLANT DISEASE 225 elliptic, surrounded by a mucilaginous layer, 24-32 x 12-18 jj.; paraphyses exceeding the asci. The mycelium produces rot of cranberries, also leaf spots, but the fructification of the fungus is rarely found in nature except on Fig. 159. — A single perithecium of A. vaccinii taken from a pure culture on corn meal. After Shear. Fig. 160. — Acan- thorhynchus; a germinating aa- cospore bearing the peculiar appressorium, 17, view from above. After Shear. old fallen leaves. In culture, however, it produces abundant peri- thecia. When on the leaf the perithecia are subepidermal and are sparsely scattered over the lower surface. No conidial or pycnidial form is known. Remarkable appressoria are produced by the germ tubes from the spores, Fig. 160. Sphaeriaceae (p. 222) Perithecia single or clustered, free or with a false stroma in which they are more or less sunken; walls leathery, horny or woody; ostiole rarely elongate, usually papillate; spores frequently ap- pendaged. The family is distinguished by its free perithecia with papillate ostioles. It contains about seven hundred species. Key to Genera of Sphaeriaceae Perithecia hairy above, rarely smooth above and hairy beneath Spores 1 or 2-celled Perithecia thin, cuticulate or leathery Spores 1-ccllcd; asci apically thick- ened 1. Niesslia. 226 THE FUNGI WHICH CAUSE PLANT DISEASE Spores 2-celled; asci not apically thickened 2. Coleroa, p. 227. Perithecia thick, leathery or carbon- ous Spores hyahne, sometimes becoming brown, 1 or 2-cellecl Spores elHpsoid 3. Trichosphaeria, p. 228. Spores cylindric, bent 4. Leptospora. Spores dark colored, 2-celled 5. Neopeckia. Spores more than 2-celled Perithecia thin, leathery or cuticula- rized 6. Acanthostigma, p. 229. Perithecia thick, carbonous or woody Spores 4-celled, the two middle cells brown, the end cells hyaline. .. . 7. ChaetosphaBria. Spores many-celled, concolorous, hyaline or brown Spores spindle-form 8. Herpotrichia, p. 229. Spores elongate-cylindric 9. Lasiosphaeria. Perithecia smooth Perithecia tuberculate or irregularly thickened Spores ellipsoid, 2 to many-celled, hyaline 10. Bertia. Spores spindle-form, 4 to 11-celled, hyaline 11. Stuartella. Spores muriform, dark 12. Crotonocarpia. Perithecia not tuberculate Spores 1-celled, dark Spores with hyaline appendages on each end; perithecia thick, leath- ery 13. Bombardia. Spores unappendaged, perithecia carbonous 14. Rosellinia, p. 230. Spores 2 to many-celled Perithecia thin, leathery; spores 2- celled 15. Lizonia. Perithecia thick, leathery or car- bonous, brittle Spores ellipsoid Spores 2-celled THE FUNGI WHICH CAUSE PLANT DISEASE 227 Spores hyaline, somotiinos hc- coiniiijJ! brown Ki. Spores hyaline to green 17. Spores dark-colored IS. Spores 3 to many-celled Spores hyaline 19. Spores dark-colored 20. Spores elongate, spindle-form, hya- line, many-celled 21. Bombardiastrum Melanopsamma. Thaxteria. Sorothelia. Zignoella. Melanomma. Coleroa Fries (p. 226) Perithecia free, small, globose, flask-shaped; asci 8-spored; spores Fig. 161. — C. chsetomium. C, perithecia; D, asci. After Lindau and Winter. ovate, 2-celled, hyaline, green or golden-brown; paraphyses poorly developed. Comdia=Exosporium. This genus, of some thirteen species all of which are parasitic, is quite similar to Venturia. The chief economic species are C. chaetomium (Kze.) Rab. (Conidia=Exosporium rubinus) on Rubus in Europe and C. sacchari v. B. d H., on sugar cane in Java.^^^ 228 THE FUNGI WHICH CAUSE PLANT DISEASE Trichosphaeria Fuckel (p. 226) Perithecia usually free, globose, woody or carbonous, hairy, ostiole flat or papillate; asci-cylindric,8-spored; spores 1 to 2-celled, hyaline; paraphyses present. There are some forty species, mainly saprophytes. T. sacchari Mass.^^^' ^^^ Perithecia broadly ovate, dark-brown, beset with brown hairs; spores elongate-ellipsoid, 1-celled; the conidial forms are various Fig. 162. — Trichosphaeria. E, habit sketch; G, conidial stage. After Lindau, Winter and Brefeld. and their genetic connection is by no means certain. (1) (=Conio- thyrium megalospora) Pycnidia 1-3, on a dark-colored, parenchy- matous stroma; conidia elongate, straight or curved, brownish, 12 X 5 iu, (2) The macroconidia (=Thielaviopsis ethaceticus) see p. 596, are often found forming intensely black, velvety layers lining cracks and cavities in diseased canes. (3) Micro- conidia produced on the surface in Oidium-like chains. Their connection with this fungus is disputed and uncertain,^^^ It is a sugar cane parasite. THE FUNGI WHICH CAUSE PLANT DISEASE 229 Acanthostigma de Notaris (p. 226) Perithecia free, globose or ovate, very small; walls leathery, black, beset with stiff bristles, ostiolc short; asci usually cylindric, rarely ovate, 8-spored; spores spindle-shaped, multicellular by cross walls, hyaline; paraphyses few or none. There are some thirty species, mostly saprophytes. A. parasiticum (Hart.) Sacc.^^''"^^^ Perithecia globose, minute, with rigid divergent hairs, 0.1-0.25 mm. in diameter; asci 50 /j, long, early disappearing; spores fusoid, straight or curved, smoky, 15-20 /t, continuous or 2 to 3-septate. Common on leaves of Abies, Tsuga and other conifers in Europe and America. The hyaline mycelium grows on the lower sides of branches and onto the leaves killing them and matting them to the branches. The mycelial cushions later turn brownish and eventually very small perithecia form on them. Fig. 1G3.— Peiithecium of A. Tri- chosphocria parasiticum, show- ing ostiole, bristles, asci, para- physes and spores. After Hartig. Herpotrichia Fuckel (p. 226) Perithecia superficial, globose or subglobose, texture firm, coriaceous to subcarbonous, hairy or smooth, ostiole papillate or not; asci oblong to clavate; spores fusiform, 2 or many-celled, hyaline or brown; paraphyses none. The species, numbering about twenty-five and growing on woody plants, are mostly saprophytes. H. nigra Hart.^^^ Mycelium dark-brown, widely spreading, haustoria slender, lighter in color; perithecia globose, dark, 0.3 mm. in diameter; asci elongate, 76-100 x 12 /x; spores constricted, 1-3 septate. 230 THE FUNGI W HICH CAUSE PLANT DISEASE Common in Europe on branches of Larix, Abies, Juniperus, spruce and pine, doing great damage. The dark-bro\\Ti myceUum grows over the plant, killing and matting the leaves. Rosellinia Cesati & de Notaris (p. 226) Perithecia superficial, but often with the bases more or less sunken in the substratum, coriaceous or car- bonous; brittle, spherical or ovate, bristly or not; asci cylindric, 8-spored; spores elliptic, oblong or fusiform, 1-celled, brown or black; paraphyses fusiform. Conidia of the type of Coremium, Sporotrichum, etc. In most cases the active parasitic stage occurs on roots and consists of a vigorous white mycelium, which remains for a long time Fig. 1G4. — Herpotri- sterile, developing large branching and inter- chia. B, ascus; . i /-r^. \ i • i i C, spore. After lacmg rhizomorphs (Dematophora) which later ^"*^^' become brown. These resemble somewhat, but are distinguishable from, the rhizomorphs of Armillaria mellea; again, they are Rhizoctonia-like. There are over one hundred seventy species, mostly saprophytic. R. necatrix (Hart.) Berl.^™- ^'^ A destructive fungus, long known as Dematophora necatrix, possesses a white mycelium which invades the small roots, thence passes to larger ones, extending in trees through the cambium and wood to the trunk, occasionally rupturing the bark and pro- ducing white floccose tufts. Sclerotia of one or more kinds are produced in the bark and often give rise to conidia on tufted conidi- ophores in a Coremium-like layer (Fig. 165). The mycelium, when old, turns brown and produces large branching, interlacing rhizomophic strands which spread to the soil, or wind about the roots. In some instances the connection of the ascigerous with the sterile or conidial stages is well established; in others the asci have been found but rarely and the evidence of genetic connection is not complete. It is probable that some fungi reported as Dema- tophora do not in reality belong to Rosellinia. The fungus attacks nearly all kinds of plants. THE FUNGI VVmCIl CAUSE PLANT DISEASE 231 KA ?.»>- Perithecia wore found by Viala ^^^ and by Prillieux ^^^ on old wood, long dead from such attack. These belong to the genus Rosellinia and are believed to present the ascigerous form of Dema- tophora necatrix. Similar claims of relationship of this fungus to several other genera have been made and its actual position cannot be consid- ered as established with certainty. R. massinkii Sacc. Perithecia sparse, globose or depressed, carbonous, 165 At; asci cylindric, 54 x 8 IX] spores dark-brown, el- liptic, 1-rowed, 10 x 5 /i. It is reported by Halsted on hyacinth bulbs. R. bothrina B. & Br. is the cause of a tea root disease. Pseudodematophora closely allied to the above forms is described by Beh- rens ^'^ on diseased grape roots. R. quercina Hart, is parasitic on roots and stems of A^oung oaks, producing a Rhizoctonia-like mycelium, at first white, later brown. Perithecia are usually abundant. Black sclerotia the size of a pin head are also present superficially. R. radiciperda Mas. closely allied to R. necatrix, affects a large number of hosts, among them apple, pear, peach, cabbage, and potato. An undetermined species of this genus is said to cause a cran- berry disease.'^'' Shear, however, in his extensive studies of cran- berry diseases, did not find it. R. aquila (Fr.) d. Not. injures Morus. Its conidial form is Fig. 1G.5. — R. necatrix. 4. corcniiuni and co- nidia; 5, perithecia extruding spores; 6, asci and paraphyses. After Hartig, Prillieux and Viala. 232 THE FUNGI WHICH CAUSE PLANT DISEASE Sporotrichum fuscum. R. ligniaria (Grev.) Nke. occurs on ash trees. R. echinata Mas. is reported on "all kinds of Dicotyledon- ous shrubs and herbs." Melonomma Fcl. in the species M. henriquesianum Bros. & Roum. is parasitic on cacao stems. M. glumarum Miy. is on rice.^"^ Ceratostomataceae (p. 222) The fungi of this family are very similar to the Sphseriaceae, but are distinguished by less pronouncedly carbonous perithe- cia which may be merely membranous, and open by an elongate, beak-like ostiole. It is a family of only about one hundred twenty-five species, chiefly saprophytes. Key to Genera of Ceratostomatacese Spores 1 -celled Spores hyaline 1. Ceratostomella, p. 232. Spores brown 2. Ceratostoma. Spores 2-celled Spores hyaline 3. Lentomita. Spores dark-colored Perithecia on a cottony stroma 4. Rhynchomeliola. Perithecia not on a cottony stroma. . . 5. Rhynchostoma. Spores many-celled Spores with cross walls only Spores elongate, 4 to many-celled, hya- line or brown 6. Ceratosphaeria. Spores filiform, many-celled, usually hyaline Perithecia erect, astromatic 7. Ophioceras. Perithecia horizontal in stromatic nodules 8. Cyanospora, p. 233. Spores muriform 9. Rhamphoria. Ceratostomella Saccardo Perithecia superficial, firm; asci ovate, 8-spored, disappearing early; spores elongate, blunt or pointed, 1-celled, hyaline. About thirty species. An extensive study of the genus was made by THE FUNGI WHICH CAUSE PLANT DISEASE 233 Hedgcock ^^^ who recognizes several species as discoloring lumber. 13 C. pilifera (Fr.) Wint. has been described in detail by von Schrenk as the cause of a blue color in pine wood.'^ ^ Cyanospora Heald & Wolf (p. 232) Perithecia solitary or in clusters of two or three on stromatic nodules, immersed, horizontal; ostiole lateral, neck short; asci Fig. 166. — C. pilifera peri- Fig. 167. — C. albicedrae. Sec- thecium, asci and tion of a perithecium in spores. After von its stroma. After Heald and Schrenk. Wolf. Fig. 168.— C. albicedrte. Upper part of an ascus showing thickened apical wall and coiled spores. After Heald and Wolf. slender, linear, surrounded by a gelatinous matrix, apically thick- ened; spores filiform, multiseptate, hyaline. A single species. C. albicedrae Heald & Wolf. Stroma on bark or wood of the host, varying from gray on the bark to black on wood, lenticular, 1-2 mm. long, solitary or clus- tered; perithecia 825-1200 x 260-400 n; asci 700-1100 x 8-10 m; spores 600-1000 x 3 m; paraphyses numerous, continuous, 1 /x in diameter. The fungus is described in detail by Heald and Wolf ^^^ as caus- 234 THE FUNGI WHICH CAUSE PLANT DISEASE ing whitening of the mountain cedar (Sabina sabinoides) from Texas to Central Mexico. The seat of infection is the younger twigs and the young trees, especially where in shade. The disease may kill the entire trees. Cucurbitariaceae (p. 222) Perithecia clustered, immersed at first, then erumpent, seated on a stroma, leathery to carbonous; paraphyses present. The species numbering about one hundred fifty are mostly saprophytes. Key to Genera of Cucurbitariaceae Spores 1-celled Asci 8-spored Spores large, green 1. Bizzozeria. Spores suuiU, hyaline 2. Nitschkia. Asci many-spored 3. Fracchiaea. Spores 2 or more-celled Spores 2-cclled Perithecia bristly, spore walls hyaline. . 4. Gibbera, p. 234. Perithecia smooth, spore walls brown. . 5. Otthia. Spores more than 2-celled 6. Gibberidea. Spores muriform 7. Cucurbitaria, p. 234. Gibbera Fries 179 Perithecia cespitose on a superficial, thick, Demataceous, conidia- bearing, carbonous, fragile, bristly stroma; ostiole papillate; asci cylindric, 8-spored; spores oblong, elliptic, hyaline, uniseriate. The genus contains some half dozen species, one of which G. vaccinii (Sow.) Fr. occurs on Vaccinium in Europe. The conidial form is Helminthosporium vaccinii. Fig. 169. Cucurbitaria Gray Perithecia cespitose or more rarely gregarious on a crustaceous stroma covered by Demataceous hyphse, spherical, glabrous, black, coriaceous; asci cylindric, 8-spored; spores uniseriate, oblong or elliptic, muriform, brownish, paraphyses present. THE FU-NDi WlilCii CAl SK I'LA.X T DlriEASE 235 Over seventy species, several of whicli are parasitic but noii" of importance in America. C. laburni Pers. is on branches of Cytisus; C. sorbi Karst on Sorbus twigs; C. pityophila (Kze.) d Not. on various conif(>r twigs; C. berberidis (Pers.) Gray on Rerberis; C. elongata (Fr.) Grev. on Robinia; C. piceae Brothwick, on Picea. Mycosphaerellaceae (p. 223) Perithecia mostly subei)idcrmal, rarely subcuticular, finally more or less erumpent or even superficial, membranous or leathery, D Fig. 1G9. — Gibbera vac- cinii. An asms. After Winter. Fig. 170. — Cucurbitaria berberidis. G, habit sketch ; H, ascus. After Lindau and Winter. fragile; asci fasciculate, 8-spored; spores variable, septate, rarely muriform, hyaline to dark-brown; paraphyses none. This family of over seven hundred species contains many sap- rophytes and several very important parasites. Key to Genera of Mycosphaerellaceae Spores 1 to 2-cclled Spores hyaline or green Spores 1-cellcd or not clearly 2-ccllod Perithecia very small, on a basal growth of thick branched hyplia^ 1. Ascospora, p. 236. 236 THE FUNGI WHICH CAUSE PLANT DISEASE Perithecia without such a basal growth Spores typically 1-celled 2. Massalongiella. Spores usually unequally 2-celled . 3. Guignardia, p. 237. Spores 2-celled Perithecia produced on living plants 4. Stigmatea, p. 243. Perithecia appearing after the death of the host 5. Mycosphaerella, p. 243. Spores dark-colored Spores 1-celled 6. Miillerella. Spores 2-celled Lichen-inhabiting 7. Tichothecium. Not lichen-inhabiting 8. Phaeosphaerella. Spores several-celled, hyaUne Spores elongate, with cross walls only Spores 2 to 4-celled ; on lichens 9. Pharcidia, p. 250. Spores 4-celled ; with a cottony subicu- lum 10. Sydowia. Spores many-celled 11. Sphaerulina, p. 250. Spores muriform 12. Pleosph3erulina,p.250. Ascospora Fries (p. 235) Perithecia borne on a subiculum of thick, brown, much-branched hyphse, globoid, black, carbonous; asci clavate, clustered, 8-spored, small; spores 1-celled, hya- line; paraphyses none. About half a dozen species, one of which is F 171 — A~^ ^^^^ ^y Vuillemin ^^^ to be the ascigerous form himantia. Asci. of CorjTieum beyerinckii, a wound parasite common on drupaceous trees causing gum- mosis. Cultural evidence of this relationship is lacking, but his hypothesis may be tentatively assumed. A. beyerinckii Vuil. Perithecia black, depressed-globose, apapil- late; ostiole indistinct or absent, 100-130 /i in diameter; spores elliptic-fusoid, ends obtuse, continuous, hyaline, guttulate, 15 x 5- 7 n. Conidia, 1. (=PhylIosticta beyerinckii) pycnidia globoid with hyaline spores. THE FUxXGI WHICH CAUSE PLANT DISEASE 237 Conidia, 2. (=Cor}Tieuin beyerinckii) conidiophores short, crowded, from a minute subepidermal stroma; conidia single, elliptic-oblong, 1 to 5-septate, brown, about 36 x 15 /x. On drupaceous hosts. In spots on the bark the mycelium is often sterile, but when it becomes old distinct pustules usually show in a well developed subepidermal stromatic tissue and from these pustules, as they rupture the epidermis, the conidiophores are produced. Conidia usually abound on the surface of twigs which have borne affected leaves. They germinate readily and produce either a sooty super- Fio. 172. — Section through a Coryneum pustule on peach. After Smith. ficial mold or if on new bark enter the host tissue and induce spotting. The conidial stage (Coryneum) of the fungus was grown in arti- ficial culture by Smith ^^^ but no ascigefous stage corresponding with that of Vuillemin was found. A. geographicum (D. C.) Desm. is common on leaves of pome fruits and A. padi Grev. defoliates cherries in Europe. Guignardia Viala & Ravaz (p. 236) Perithccia sunken, globoid or flattened, black, leathery; ostiole flattened or papillate; asci clavate, 8-spored; spores elhpsoid or fusiform, hyaline, somewhat arched, 1 or 2-celled; paraphyses none. 238 THE FUNGI WHICH CAUSE PLANT DISEASE Over one hundred thirty species are known. Some are impor- tant parasites. Conidial forms are found in Phoma and Phyllosticta. G. bidwellii (E.) V. & R.®^' '^'""^ Perithecia minute, globose, subepidermal, erumpent, perforate; asci clavate-cylindric, obtuse, 60-70 x 10-13 fx; spores elliptic to oblong, continuous, 12-17 x 43^-5 /x. Conidia ( = Phoma uvicola, Phyllosticta labruscae, Nsemospora ampelicida) borne in pycnidia 180 x 180 n, subepidermal, elliptic. 8(76CO6p0re5 W • ^ ^aa" '^ mqermm/zo/r Fig. 173. — Diagrammatic section of a perithecium con- taining ascospores. Germination of a spore at the right. After Reddick. thick-walled; conidiophores short, simple; conidia ovate to elliptic, 8-10 X 7-8 n. Filiform microconidia ("spermatia") are borne in flask-shaped pycnidia 0.1-0.2 x 0.45-0.46 n. The fungus has been placed successively in the genera Sphseria, Physalospora, Lsestadia and Guignardia. rt CO An extensive synonomy is given by E. Rose who concludes that the name should be G. ampelicida. It is found on all green parts of Vitis and Ampelopsis, the as- cigerous stage common only on the mummified fruits. Perithecia were first found in 1880 by Dr. Bidwell in New Jersey. They are abundant on berries, which have wintered out doors. Reddick admirably describes the development of the spots as follows: THE FUNGI WHICH CAUSE PLANT DISEASE 239 On the leaves the first evidence of the spot is the sH^ht blanching of a single one of the smaller areola of the leaf. Soon the blanch- ing extends to adjacent arcoliE, and if an areola is entered it is usually entirely involved. The small veinlets form the margin of the spot so that the outline is finely crenulate. By the time the spot is .3 to .4 mm. in diameter it has a cinereous appearance. The margin, while sharply defined, is not changed in color. By the time the spot is 1 mm. in diameter, the margin appears as a black line, while the remainder of the spot is grayish-brown. A Spores...^ © ® Germinated 0cy= spores Fig. 174. Diagrammatic section through a pyciiidium, show- ing how the spores are produced and how they germinate. After Reddick. little later the margin is a brownish band and the browTi gradually extends inward until the whole spot is covered. As soon as the browTi band attains some width the blackish line on the margin is to be seen again. A second wave of deeper brown may pass across the spot but sometimes it does not get entirely across and thus leaves a marginal band of a deeper bro^\^l than the central disc. Spots vary in size from 1 mm. up to 8 mm. in tliamcter, but in general are 3 to 5 mm. or larger. Occasionally the whole leaf is destroyed but this is by the coalescence of many spots. When the spot has attained full size pycnidia protrude from under the cuticle and either dot the entire surface of the spot \\'ith minute specks or are more often confined to a more or less concentric ring. The different shades of color are apparent on the under side of 240 THE FUNGI WHICH CAUSE PLANT DISEASE the leaf on such varieties as have leaves which are smooth beneath. The pyncidia, however, have never been seen on the under side of the leaf in our varieties. On stems, tendrils, peduncles, petioles and leaf veins the spot in its first appearance is a small darkened depression which soon becomes very black. On a cane the lesion rarely extends more than a quarter of the way round, while on a tendril or leaf petiole it may extend from half to all of the way round. On shoots, the lesions never extend so deep as to cut off the sap supply, but on petioles this occasionally happens, rarely so on peduncles, and quite commonly so on pedicels and tendrils. The first indication of Black Rot on the berry is the appearance at some point of a small circular blanched spot, scarcely 1 mm. in diameter. The blanching is so slight as to be detected only by careful observation. It rapidly becomes more apparent and has a whitish appearance, the contrast becomes more ap- parent by the appearance of a brownish line at the mar- gin. The whitish center increases in size and the brownish or reddish-brown ring increases in diameter as well as in width and is quite evident when the spot is 2 mm. in diameter. When the spot is 3 mm. in diameter the ring is one-half mm. in width and enough darker to give a bird's eye effect (a light circular disc with an encircling darker band). The spot rapidly increases in size so that in twelve hours more it may be 6 to 8 mm. in diam- eter, and the encircling band nearly 2 mm. in width. After five hours more, the spot is 8 or 9 mm. in diameter and there begins to appear an outer darker band and an inner lighter brown one which have in some cases a much lighter line between them. The aureole is thus composed of two or three bands or rings. Eighteen hours later, the spot is 1 cm. or more in diameter, is distinctly flattened, and numerous minute brown specks appear on the Fig. 175. — Section of a pustule showing microconidia. After Longyear. THE FUNGI WHICH CAUSE PLANT DISEASE 241 white center of the spot. In five hours more they are so numerous as to give a blackish appearance. In New York, Reddick found that the asci begin to ripen in May and continue to mature throughout the summer being still abundant in October. The asci swell in water often to twice the length given above; spores are forcibly ejected from the asci at maturity, being thro\vTi to a height of 2 to 4 cm. There is at one end of the asco- spore a hyaline vesicle which probably aids in fixing it to the host.^^^ They germinate but slowly, requiring from thirty-six to forty-eight hours to show germ tubes. Reddick deter- mined the incubation period on fruit as from eight to twenty-one days and found that only tender leaves still growing are susceptible. The berry is susceptible even after the calyx has fallen. The pycnidial spores are said by some to show a hyaline appendage ^^^ though others by careful study fail to find it.^^'^ These spores often live over winter. ^^° The Fig- 176.— g. bid- ... 1 . I 1 1 • • T • -1 wellii; ^5, nearly ma- microconidia which develop m pycnidia similar ture ascus with to those of the macroconidia do not occur so Iscospores-' ;2™^ger- abundantly early in the season as they do minating ascospores. -' '' . ... 29, same with ap- later and seem to be mainly limited to the pressoria. After fruits. Sporeless pycnidia, pycnosclerotia, also occur and may eventually develop into perithecia. Conidia on hyphse of questionable relationship to the fungus are sometimes seen. Reddick ^^^ secured pure cultures in the following ways. 1. In poured plate dilution of asci; some twenty days were required. 2. By inverting a plate of sterile agar over a bunch of mature mummies floating on water. The ejected ascospores thus clung to the agar and gave pure cultures in ten days. 3. By aseptic transfer of the mycelium. 4. By aseptic transfer of pycnospores. Artificial infections have been reported in Europe from both conidia and ascospores: Reddick, who made many thousand in- 242 THE FUNGI WHICH CAUSE PLANT DISEASE •oculations under all conceivable conditions, failed utterly of posi- tive results. From the Caucasus Prillieux and Delacroix ^^^ have described a Guignardia causing a black rot of grapes which is regarded as distinct from the usual American form, differing both in the peri- thecial and conidial stages. This is called G. baccae (Cav.) Jacz. Its conidial form Phoma reniformis eventually covers the whole berry with pustules. Two kinds of pycnidia are described. G. vaccinii Sh.^^^' ^'' Perithecia on young fruit or flowers, sub- epidermal, globose, walls thick, carbonous; asci clavate, 60-80 n long; spores elliptic or subrhomboidal, hyaline, becoming tinted. /^^^ ^ ^^ Conidia (=Phyllosticta) borne in pycnidia Fig. 177.— A vertical sec- similar to the perithecia but thinner- walled, oTcu'ignardi'avaccinii! 100-120 Mi conidia hyaline, obovoid, 10.5- showing asci. After 13 5 ^ 5-6 ,jl. On Vaccinium. Shear. '^ In the decaying berries all sporing forms of the fungus are rare though in the softened tissues fungous hyphae abound. Transferred to culture media these hyphse grow readily and produce spores abundantly. The conidial form is common in artificial culture; the peri- thetical form comparatively rare. Pycnidia on leaves are sub- epidermal, usually hypophyllous, and are quite abundant. The spores at maturity issue in coils from the ostiole. The fungus was studied extensively in artificial culture by Shear, wet sterilized cornmeal proving a most suitable medium. Pycni- dia appeared in four to eight days after inoculation and spores were mature at twelve to eighteen days. Both pycnidia and perithecia were obtained in pure cultures. The rarity of cultures able to pro- duce perithecia is explained by Shear on the assumption "that there is some inherent potentiality in the mycelium of the fungus in certain strains, races, or generations which causes it to produce the ascogenous stage whenever conditions for its growth are favora- ble, i. e., on favorable culture media without special reference to their exact composition or environment or on the leaves of its nat- ural host." Conclusive infection experiments have not been made. THE FUNGI WHICH CAUSE PLANT DISEASE 243 G. theae Born. '^^ ^rows on tea leaves. G. (Laestadia) buxi Desm. The perithecia develop on box leaves. It is probably saprophytic although sometimes considered a parasite. Stigmatea Fries (p. 236) Perithecia subepidermal, or subcuticular, thin, black; asci oblong, subsessile, 8-spored; spores ovoid-ellipsoid, 2-celled, yel- lowish or hyaline; paraphyses present. The ascigerous stage of two species of Entomo- sporium are said by Lindau to belong to this genus. Atkinson, however, places them in the genus Fabrea, see p. 149. S. juniperi (Desm.) Wint., on living leaves of Juniperus in Europe and America and on „ ,„„ „.• . . . . ' Fig. 1<8. — fetigmatea. Sequoia in California. Asci and spores. Perithecia scattered, lenticular or subhemi- spheric, rough, 200-300 fj. in diameter, asci rounded and obtuse above, abruptly tapering below into a short stipe, 60-70 x 20 ju; spores ovate-lanceolate, unequally 2-celled, yellowish-hyaline, 16- 25 X 6-8 n. S. alni occurs on alder leaves in Europe. Mycosphaerella Johans. (p. 236) Perithecia subepidermal, suberumpent, globose-lenticular, thin, membranous, ostiole depressed or short papillate; asci cylindric to clavate, 8-spored; spores hyaline or greenish, ellipsoid, 2-celled; paraphyses none. This large genus of over five hundred species formerly known as Sphserella contains several serious plant pathogens. It is often found in its conidial forms as: Ramularia, Ascochyta, Septoria, Phleospora, Cercospora, Ovularia, Cylindrosporium, Phyllosticta, Graphiothecium, Phoma, Diplodia or Soptoglocum. In many cases the relationship of the ascigerous and conidial forms is as yet but imperfectly known. The perithecia are usually found late in the season, often only on leaves that have borne the conidial stage in the summer and have then wintered. 244 THE FUNGI WHICH CAUSE PLANT DISEASE M. fragariae (Tul.) Lin.^^^ Perithecia on leaves, are produced late in the season, globose, subepidermal, membranous, black, thin-walled; asci few, clavate, Fig. 179. — Mycosphserella fragariae. b, conidiophores burst- ing through the epidermis; c, arising from apex of a pycnidium; d, summer spores, one germinating; e, section of a spermogonium; /, section of peritheeium; g, ascus containing eight two-celled spores. After Longyear. 8-spored, 40 n long; spores hyaline, 2-celled, with acute tips, 15 X 3-4 At. Conidia (=Ramularia tulasnei) abundant in early summer on reddish spots, stromatic, conidiophores simple; conidia elliptic 20-40 X 3-5 fi, 2 to 3-celled. On Fragaria. The life history was first studied in 1863 by the Tulasne brothers under the name Stigmatea. The generic name was changed to Sphaerella in 1882 and later to Mycosphserella. THE FUNGI WHICH CAUSE PLANT DISEASE 245 The slender mycelium pervades the diseased areas disorganizing the host cells and resulting in reddish coloring of the sap. Ob- servations of Dudley ^^^ indicate that the mycelium or portions of it can remain alive over winter in the host tissue ready to produce abundant conidia in the spring. The most abundant conidial stage is the Ramularia-form (Fig. 179) which abounds all summer. Sowings of these conidia, under conditions of humid atmosphere, result in characteristic spots in from ten to eighteen days. Toward winter sclerotial bodies are formed from the mycelium. These in culture dishes have been seen to produce the typical summer conidia. Some of these sclerotia-like bodies have been reported as "spermogonia," bearing numerous "spermatia" 1 x 3 m- Perithecia abound in au- tumn. These are larger than the spermogonia and are usually embedded in the leaf tissue, though they sometimes appear super- ficially. Conidiophores are often borne directly on the perithecium wall. Ascospores germinate within the ascus. From the mycelium resulting from ascospores Dudley ^^^ observed the formation of typical summer conidia. M. grossulariae (Fr.) ^^^ Perithecia hypophyllous, gregarious, spherical, with minute ostiole, black; asci short-pedunculate, clavate, 55-66 x 8-12 n; spores fusoid, filiform, curved or straight, uniseptate, hyaline, 26-35 X 3-4 n. It has been reported on the gooseberry associated with Cer- cospora angulata and Septoria ribis. M. rubina (Pk.) Jacz.^oo Perithecia minute, gregarious, submembranous, obscurely papil- late, subglobose or depressed, erumpent, black; asci cylindric, subsessile, 70-80 x 10-12 )u; spores oblong, obtuse, uniseptate, generally constricted in the middle, 15 x 6-7 n, upper cell broadest. Conidia ( = Phoma) are associated with the perithecia and are supposed to be genetically connected with them as is also a second spore form ( =Coniothyrium). The species is held responsible for bluish-black spots on rasp- berry canes. M. cerasella Aderh.^"^ is reported as the perithecial stage of Cercospora cerasella common on cherry. 246 THE FUNGI WHICH CAUSE PLANT DISEASE ■ X, ■ ,/r''"'" '■'-^ ' ' ■ , ' ! m'',^ ■ "S^ • ' ' i ,' J- ■ :■■ ■ y. ' ; . i '', V' ■v.'..'^:, >: ■- ' ■' n-. ' •■' , ^'■'''■■":'V . i^^'-----^-' ^-■' <■' a /, - ^ Fig. 180. — M. sentina, tSeptoria stage. Portion of a section through a pear leaf spot, showing e, e, epidermis; p, pali- sade cells sp, spongy parenchyma; a, S. piricola pycnidium, giving out spores, 6. After Longyear. M. sentina (Fr.) Schr. Perithecia, 80-110 /*; on dead spots of leaves, the long ostiole erumpent; asci clavate, 60-75 x 11-13 ^u, colorless; spores fusiform, curved or straight, 26-33 x 4 II. Conidia (=Septoria piricola) borne in pycnidia which are similar in size and form to the perithecia; conidia filiform, curved, 3-celled, 40-60 x 3 m- On pear and apple. The conidial form was men- tioned in America as early as 1897 by Atkinson 204 and was the subject of a comprehensive bulletin by Duggar in 1898.203 The ascigerous stage was demon- strated by Klebahn in I9O8.202 The pycnidia, mainly hypophyllous, are sunk deeply into the leaf tissue and are surrounded by a delicate pseudoparenchyma. The conidia are distinctly tinted, green or smoky. The perithecia are numerous, and crowded on grayish spots, hypophyllous, on old wintered leaves. They are without stroma. Klebahn by "inoculations (June, 1904) with ascospores secured spots in fifteen days and pycnidia in twenty- nine days, bearing the characteristic conidia. From ascospores he also made pure cultures which soon developed pycnidia with conidia. Pure cultures made from conidia in the hands of both Klebahn and Duggar have failed to give typical perithecia. M. citrullina (C. 0. Sm.) Gros. Perithecia roughish, dark-brown or black, depressed-globose to inverted top-shaped, usually with a papillate ostiole, densely scattered, erumpent, 100-165 11; asci cyiiadric to clavate, 45-58 x 7-10 n\ spores hyaline, oblong-fusoid, constricted at the sep- tum. Fig. 181. — M. sentina. Conidial layer, co- nidiophores and co- nidia. After Kle- bahn. THE FUNGI WHICH CAUSE PLANT DISEASE 247 Conidia ( = Diplo(lina citriillina) Pycnidia similar to the peri- thecia, spores 2-celled, hyaline, straight or curved, more or less cylindric, 10-18 x 3-5 n. The fungus was isolated in pure culture by Grossenbacher ^"^ from muskmelons by direct transfer of diseased tissue to potato agar. Inoculations from these cultures proved the fungus capable of entering healthy uninjured tissue, the • disease showing about six days after in- oculation. The brownish pycnidia origi- nate from an extensive subepidermal, partially cortical, much-branched, brown- ish mycelium but soon break through and , , r • 1 ^^Tl • FiG. 182. — M. sentiiiu. A, appear almost superfacial. When mois- perithecium and asci. Af- tened, spores issue in coils. Darker peri- ^^^ Klebahn. thecia, nearly superficial, are found on old diseased spots. Both ascospores and conidia are capable of causing infection. Inocu- lations on pumpkin and watermelon gave positive results; these on cucumber. West Indian gherkin, squash, pumpkin, and gourd were negative. The same fungus has been reported as cause of canker of tomatoes. -''^ M. tabifica (P. & D.) Johns.^o^-z^" Perithecia rounded, brown; asci oblong-clavate, 8-spored; spores hyaline, upper cell larger, 21 x 7.5 /x. Pycnidia (=Phoma) subglobose; conidia elliptic, hyaline, 5-7 x 3.5 fi, escaping as a gelatinous cirrus. This conidial form, common on beets causing leaf spot through- out the summer, is said by Prillieux and Delacroix to be connected with M. tabifica the perithecial form, which is found upon the dead petioles at the end of the season. Convincing evidence "^^ of this connection seems wanting. The conidial stage ^°^ is variously known as Phoma beta, Phoma sphserosperma, Phyllosticta tabifica. The Phoma-form from stems and rotten roots and the Phyllosticta-forms from leaves were both studied by Hedgcock ^^" in pure cultures on many media and many inoculations were made, all leading to the conclusion that the Phoma and the Phyllosticta are identical. M. tulasnei Jacz.-" Perithecia subglobose, minute; asci cylindric fusoid; spores 248 THE FUNGI WHICH CAUSE PLANT DISEASE oblong, rather pointed, upper cell in the ascus somewhat larger than the others, 28 x 6.5 fi. Conidia of two kinds, (1) (=Cladosporium herbarum) tufts dense, forming a velvety blackish-olive, effused patch, conidio- phores erect, septate, rarely branched, often nodose or keeled; conidia often in chains of 2 or 3, subcylindric pale-olive, 1 to 3-septate, 10-15x4-7 /x. (2) ( = Hormodendrum cladosporioidies Sacc.) Hyphae erect, simple, bearing apically or laterally a tuft Fig. 183. — M. citrullina, A. pycnidium (Diplodia) in sec- tion, B, perithecium; C, ascus and spores. After Grossen- bacher. of small, eUiptic, continuous, brown conidia in simple or branched chains. It is the cause of serious disease in Europe, being especially injurious to cereals after a rainy season preceded by a drought and is found also parasitic on pea, apple, raspberry, cycad, agave and as a saprophyte almost anywhere. M. stratiformans Cobb, affects sugar cane. The perithecial stage alone is known. ^^^ Further study is desirable. M. gossypina (Cke.) Er.^^^-si^ Perithecia ovate, blackish, partly immersed, 60-70 x 65-91 fx, asci subcylindric, 8-10 x 40-45 /i; spores elliptic to fusoid, con- stricted at the septum, 3-4 x 15-18 At. Conidia (=Cercospora gossypina); hyphse flexuose, brown. THE FUNGI WHICH CAUSE PLANT DISEASE 249 120-150 ^l high; conidia attenuate above, 5 to 7-septate, hyaline, 70-100 X 3 M. On cotton. The intercellular mycelium is irregular, branched, septate, and produces tuberculate stromata from which the brownish hyphae arise. The perithecia, much less common, are partly immersed in old leaves. M. morifolia (Fcl.) Lin. in its conidial stages, Cylindrosporium mori and Septogloeum mori, affects Morus. M. maculiformis (Pers.) Schr. grows on many trees. Especially common are its conidial stages Cylindrosporium castinicolum and Phyllosticta maculiformis. M. rosigena E. & E. -'8-219 Amphigenous on reddish-brown, purple-bordered spots which are about 3-4 mm. in diameter; perithecia thickly scattered over the spots, minute, 60-75 ju, partly erumpent, black; asci sub- clavate to oblong, 25-30 x 8-10 /x; spores biseriate, clavate- oblong, hyaline, 1-septate, 10-12 x 2 /i, ends subacute. It causes leaf spots of rose in America. M. brassicaecola ( = Phyllosticta brassicsecola) grows on cabbage. M. punctiformis Pers. produces leaf spot on oak, lime, hazel; M. fagi Auser. on beech; M. pinifolia Due. on pine leaves; ^^'^ M. abietis (Rost.) Lin. a leaf disease of balsam.^^ M. taxi Cke. grows on yew; M. hedericola Desm. on Hedera leaves; M. gibelliana Pass, on Citrus leaves; M. vitis Fcl. on grape leaves; M. elasticae Kr. ^-^ on Ficus elastica. M. cydoniaB Vogl. ^^^ on quince is probably identical with M. sentina on pear and apple. M. ulmi Kleb. occurs on elm with its conidial forms, a Phleo- spora and Phyllosticta bellunensis. M. comedens Pass, is on the same host. M. larcina Hart, and its conidial form Leptostroma larcinum affect larch, causing defoliation. M. Icfifgreni N. on oranges and M. coffeae N. on coffee are tropical forms. M. populi Schr. (=Septoria populi) is on Populus.^*^ 250 THE FUNGI WHICH CAUSE PLANT DISEASE M. pinodes Berk & Blox. Perithecia numerous, 100-140 /x; asci oblong-cylindric, 58-62 x 12 ii; spores 2-rowed, 14-16 x 5. Pycnidia (=Septoria pisi), with large ostiole; spores 35-45 x 3- 3.5 n, 1 to 3-septate, On pea stem and leaves.^"^' ^^° M. primulae is on primrose; M. tamarind! on tamarinds in Africa. M. cinxia Sacc. is on lilies, causing leaf blight; M. fusca Pass, on the gladiolus; M. coffeicola on coffee in Mexico. M. shiraina Miy. and M. hondai Miy. are on rice. M. convexula (Sch.) Rand. Perithecia hypophyllous, gregarious or scattered, finally erum- pent, 100-200 ju in diameter, papillate at maturity; no paraphyses; asci fasciculate, 54-100 x 9-11 ix, 8-spored; spores allantoid, 1-septate, hyaline, 13-27 x 3.5-5.5 /t. Forming a leaf spot on pecans.^^^ An undetermined species of Mycosphaerella has been reported on the grape by Rathay.^"^ Many other species are known on ferns, cereals, lilies, and va- rious trees and herbs. In the genus Pharcidia. P. orzae Miy. is on rice.^*^^ In Sphaerulina the species Sphaerulina taxi Mass. is injurious on yew leaves. Pleosphaerulina Passer (p. 236) Perithecia subepidermal, erumpent, small, globoid or lenticular, black; asci 8-spored, clavate; spores muriform, hyaline; paraphyses none. P. briosiana Pol. causes a leaf disease of alfalfa in Italy. Pleosporaceae (p. 223) Perithecia sunken, at length erumpent, or from the first more or less free, membranous or coriaceous, usually papillate; asci clavate-cylindric, double-walled; spores variable, but usually colored, oblong, fusoid or elliptic; paraphyses present. An order of some nineteen hundred species most of which are saprophj^es, although several are parasites, some of considerable importance. THE FUNGI WHICH CAUSE PLANT DISEASE 251 Key to Genera of Pleosporaceae Spores l-ccUed Spores with blackish appendages, elon- gate, hyaline 1. Urospora. Spores unappendagcd Spores elongate, hyaline or light yel- low 2. Physalospora, p. 252. Spores elongate, fusoid, hyaline; tips bent 3. Therrya. Spores 2-celled Spores with the 2 cells very unequal in size Upper cell the smaller; parasitic on Riccia 4. Arcangelia. Basal cell the smaller; saprophytes. ... 5. Apiospora. Spores with both cells about equal Perithecia hairy; spores hyaline or brown 6. Venturia, p. 253. Perithecia smooth Spores hyaline 7. Didymella, p. 255. Spores brown Perithecia not stromatic 8. Didymosphaeria,p.256. Perithecia borne on a stroma 9. Gibbellina, p. 256. Spores more than 2-celled Spores elongate, with cross walls only Spores appendaged Spores clavate, 4 to 6-celled, brown, the basal cell hyaline long- appendaged 10. Rabentischia. Spores filiform, many-celled, with filiform appendages 11. Dilophia, p. 257. Spores not appendaged Spores fusoid or elongate, blunt, never filiform or separating into cells Spores elongate, 3 to many-celled, hyaline or brown Spores with a thick, dark-brown epispore and a thin hya- line endospore, 4-celled, cl- hpsoid 12. Chitonospora. 252 THE FUNGI WHICH CAUSE PLANT DISEASE Spores not as above, elongate 3 to many-celled hyaline or brown Perithecia hairy 13. Pocosphaeria. Perithecia smooth Spores hyahne 14. Metasphaeria, p. 257. Spores yellow or dark- brown 15. Leptosphaeria, p. 257. Spores fusoid, 7 to many-celled, the central cell enlarged and brown, the rest hyaline 16. Heptameria. Spores fusoid, up to 30-celled hya- line or brown 17. Saccardoella. Spores filiform, often separating into cells Perithecia hairy 18. Ophiochaeta. Perithecia smooth/ 19. Ophiobolus, p. 259. Spores muriform Asci 8-spored Spores appendaged 20. Delacourea. Spores not appendaged Perithecia hairy 21. Pyrenophora, p. 262. Perithecia smooth 22. Pleospora, p. 259. Asci 16-spored 23. Capronia. Physalospora Niessl. (p. 251) Perithecia subglobose, covered, membranous, or coriaceous, black, with the ostiole erum- pent; asci clavate-cylindric ; spores ovoid or oblong, con- tinuous, hyaline or subhya- line; paraphyses present. This genus contains over one hundred thirty species, a few of which are parasitic on " ^ twigs and leaves. Some spe- FiG. 184.— Physalospora Perithecia and gjes pOSSeSS a Gloeosporium ascus. After VV inter. ^ ^ as the conidial form. P. gregaria and its conidial stages Tetradia salicicola and THE FUNGI WHICH CAUSE PLANT DISEASE 253 Macrodcndrophoma salicicola cause black cankers on oziers in Ireland. 224 P. abietina P. & D.^^^ is found on Picea; P. cattleyae Maub. & Las. in its conidial form, Gloeosporium macropus--'^ parasitizes Cattleya. P. laburni Bon. is on Cytisus. P. woronini JNI. & F. is described as causing a disease of grapes in the Caucasus. ^^^ P. vanillae Zimm. is on vanilla; P. fallaciosa Sacc. on banana leaves. Venturia Cesati & de Notaris (p. 251) Perithecia superficial or erumpent, bristly, ostiolate, membra- nous, dark colored; asci sessile or short stipitate, ovate or saccate; spores oblong to ovoid elliptic, hyaline or yellowish; paraphyses usually none. The conidial stages in some cases belong to the form genus Fusicladium and constitute the parasitic portion of the life history of the fungus, the ascigerous form usually being limited to old or wintered parts of the host. There are over fifty species, several of which cause diseases. V- • \ 1 u 230, 312, 313, 350 . pinna Aderh. ' Perithecia gregarious, smooth or bristly, globoid, 120-160 /x; asci cylindric; spores unequally 2-celled, yellowish-green, 14-20 x 5-8 M- Conidia (=Fusicladium pirinum) effused, velvety, blackish-olive, conidiophores short, wavy or knotted, thick- walled; conidia ovate fusoid, olive, becoming 1-septate with age, 28-30 x 7-9 /jl. It is found on the pear wintering in perithecial form on leaves, and in conidial form, or as mycefium on twigs. V. inaequalis (Cke.) Aderh. (=V. pomi [Fries] Winter). Perithecia globose, short-necked, 20-160 ij., smooth or bristly above; asci cylindric, 40-70 n long; spores yellowish-green, un- equally 2-celled, upper cell shorter and broader, 11-15 x 4 -8 /i. Conidia ( = Fusicladium dendriticum) effused, velvety, forming dendritic patches of compact masses of erect closely septate brown mycelium; conidiophores closely septate, brown, 50-60 x 4-6 fjL, wavy or nodulose; conidia solitary, terminal, obdavate, 254 THE FUNGI WHICH CAUSE PLANT DISEASE Fig. 185. — V. inoequalis. A, portion of a section through a scab spot on apple; 6, spread- ing under and lifting the cuticle, a; c, partly disorganized cells of the apple; e, healthy cells of the apple. B, two conidiophores with summer spores /. C, spores ger- minating. Z), portion of a section showing a perithecium and asci. E, two asci, each containing 8 two-celled spores, three of which are shown at F. After Longyear. THE FUNGI WHICH CAUSE PLANT DISEASE 255 yellowish-olive, continuous when young but at length septate, 30 X 7-9 IX. Its hosts are apple and other pomaceous fruits except the pear. Conidia of special form have been known under the name Napi- cladium soraueri. The two last conidial forms have been long regarded as identical and are found in literature as Fusicladium dendriticum. The olive-green mycelium in both cases grows subepidermally in the leaf and fruit killing the epidermis and forming subepidermal stromata from which conidiophores are produced. Stromatal development is also said to be often subcuticular, resulting in a separation of the cuticle from the epidermis. The conidia are produced apically on short stalks and as each conidium is cut off the conidiophore grows forward, leaving scars equal in number to the conidia produced. Pycnidia have been reported on the mycelium in twigs in winter.^^^ Perithecia first form on the lower leaf surface in October and mature in April. They are most abundant when protected by sod or piles of leaves, and appear as small black pustules often on grayish spots. Their connection with the conidial stage was first shown by Aderhold -^^ and confirmed by Clinton. -^^ The fungus from apple was cultured on apple-leaf-agar by Clinton. Pure colonies developed in 4 to 5 days and infection was secured on leaves. Cultures from ascospores gave rise to typical conidia. V. crategi Aderh. occurs on Crataegus. V. cerasi Aderh. ( = Fusicladium cerasi) is found on cherries. Aderholt ^^^ demonstrated the connection between the ascigerous and conidial forms. V. ditricha (Fr.) Karst. ( = Fusicladium bctulse) is found on birches; V. tremulae Aderh. ( = Fusicladium tremulse) on aspen; V. fraxini Aderh. ( = Fusicladium fraxini) on ash; V. inaequalis var. cinerascens Lin. (= Fusicladium orbiculatum) on Sorbus. Didymella Saccardo (p. 251) Perithecia covered, mcml)ranous, globose-depressed, minutely papillate; black; asci cylindric or clavate* spores ellipsoid or ovate, 2-celled, hyaline; paraphyses none. 256 THE FUNGI WHICH CAUSE PLANT DISEASE Of the some one hundred twenty species D. citri N. is of in- terest since it forms cankers on orange trees in Brazil. Didymosphaeria Fuckel (p. 251) Perithecia immersed, later erumpent; asci cylindric to clavate, 8-spored; spores elliptical to ovate, 2-ceUed, brown. This genus differs from Didymella cfhiefly in the dark-colored spores. It contains some one hundred twenty species and has occasional parasitic representatives on leaves and twigs. Fig. 18G.— Didymella. A, ascus; B, hymenium of a pvTnidium. After Brefeld. Fig. 187. — Didymo- sphaeria. C, an as- cus; D, o II i d i o- phore and oonidia. After Brefeld. Fig. 188. — Dilo- p h i a graminis. J, ascus; K, spore. After Winter. D. sphaeroides (Pers.) Fr. is on Populus leaves in Europe. D. catalpae.^^^ Perithecia very small, scattered, embedded in the tissue of the leaf, pyriform to nearly spherical, varying in width from 48-104 n and in depth from 64-140 n; ostiole broadly conical, erumpent; asci 8-spored, cylindrical, usually somewhat curved; paraphyses few or wanting; spores oblong-elliptical, hyaline or yellowish, uniseptate, constricted in the middle, 9.6-13 x 3-4 /x. On Catalpa. D. populina VuilL, causes death of poplars in Europe.-^^ D. epidermidis Fr. is found on Berberis, Sambucus and Salix. Gibbellina Passerina (p. 251) Stromata black, sunken in the substratum, formed of thin, closely interwoven hyphae; perithecia sunken in the stromata, globose; THE FUNCJl W HIGH CAUSE PLANT DISEASE 257 asci elongate-globoid; spores elongate, 2-ceIIed, brown; paraphyses present. Genus of one species. G. cerealis Pers. causes a serious grain disease in Europe, es- pecially of wheat in Italy. ^^^ Dilophia Saccardo (p. 251) Perithecia sunken, not erurapent, delicate, dark-colored, ostiole papillate; asci long-cylindric; spores elongate-fusiform to filiform, multicellular, each end appendaged, the appendages hyaline, the spores hyaline or yellow. Fig. 188. There are three species, one of which D. graminis (Fcl.) Sacc. parasitizes rye and wheat in Europe. The conidial form Dilo- phospora graminis Desm. is especially common. Metasphaeria Saccardo (p. 252) Perithecia clavate, sunken in a stroma, at first covered; leathery, dark, with ostiole ; asci cy lindric to clavate, 8-spored ; spores ellipsoid, elongate, blunt or appendaged, 3 to many-celled; paraphyses filiform. M. albescens Thum. is on rice in Japan. Leptosphaeria Cesati & de Notaris (p. 252) Perithecia at first subepidermal, at last more or less erumpent, subglobose, coriaceo-membranous, globose, ostiole usually papil- late; asci subcylindric; spores ovoid, oblong or fusoid, two or more septate, olivaceous, yellowish or brown. There are about five hundred species, many of which in the conidial forms embrace Cercospora, Phoma, Hendersonia, Sporides- mium, Soptoria, Coniothyrium or Cladosporium. L. coniothyrium (Fcl.) Sacc.^^^' ^^'^ Perithecia gregarious, subepidermal, depressed, globose, black; ostiole papillate, erumpent; asci cylindric, stipitate, 8-spored, 66-96 X 4-6 fjL] spores 1-rowed, oblong, 3-septate, constricted, fuscous, 10-15 X 3.5-4 ju. Pycnidia (= Coniothyrium fuckelii), similar to perithecia; spores ovate, continuous, fuscous. It occurs on black and red raspberries and numerous other hosts. Stewart ^" verified the assumed identity of the conidial form with this ascigerous fungus by pure culture studies. 258 THE FUNGI WHICH CAUSE PLANT DISEASE L tritici (Gar.) Pass ^^^ (=Pleospora tritici). On wheat.^^® Perithecia innate, globose, black, papillate; asci clavate, short- stipitate, 8-spored; paraphyses filiform, 48-50 x 15-16 /x; spores 2-seriate, round, fusoid, 3-septate, constricted, pale, 18-19 x 4.2- 5.5. L. herpotrichoides d. Not.^^^ parasitizes rye i causing the stalks to break at the nodes; FiQ. 180. — Cross-section of raspberry bark showing two perithecia of L. coniothyriuni at the top, A, and two pycnidia of Coniothyriuni fuckelii, at the bot- tom, B. 4. An ascus of L. coniothyrium. 5. Spores of L. coniothyrium. After Stewart. L. sacchari V. B. d H. occurs on sugar-cane. L. napi (Fcl.) Sacc. (=Sporidesmium exitiosum) is found on rape; L. phlogis Bos. (=Septoria phlogis) on Phlox; L. circinans (Fcl.) Sacc. kills alfalfa roots, potato, clover, beets and other hosts; ~^^ L. vitigena Schul. occurs on grape tendrils; L. stictoides Sacc. on Liriodendron; L. rhododendri on Rho- dodendron; L. iwamotoi Miy. on rice; THE FUNGI WHICH CAUSE PLANT DISEASE 259 L. taxicola R. K. on Taxiis canadensis; L. vagabunda Sacc. spots linden branches. Its conidial form is perhaps Phoma tihse.-^^ Ophiobolus Riess (p. 252) Perithecia scattered, subglobose, submembranous, covered or suberumpent, ostiole papillate or elongate; asci cylindric; spores fusiform, hyaline or yellowish. X400 Fig. 190. — Ophio- bolus. B, asms; C, spore. After Lin(l;ui and Win- ter. X400 X£60 Fig. 191. — Pleospoia from passion-fruit. The spores are just beginning to ger- minate, the end cells start- ing first. After Cobb. A genus of some one hundred twenty-five species. O. graminis Sacc. and O. herpotrichus Sacc. occur on grasses and are quite injurious in Europe.^^^ O. oryzeae Miy. is found on rice.^''^ Pleospora Rabenhorst (p. 252) Perithecia covered at first, later more or less erumpent, usually membranous, black, globose; asci oblong to clavate; spores elon- gate or ovate, muriform; paraphyses present. 260 THE FUNGI WHICH CAUSE PLANT DISEASE Conidia occur as Macrosporium, Alternaria, Cladosporium, Sporidesmium, Phoma, Helminthosporium. There are over two hundred twenty-five species, mostly sap- rophytic. Many conidial forms whose connection to this genus have not yet been definitely proved probably belong to it and are in many instances parasites. P. tropeoli Hals, is reported as the cause of disease of the cul- tivated Nasturtium. ^"^"^ Perithecia pyriform, 140-160 /x; asci oval, one-sided, spores hyaline or very light-olivaceous, 25-35 x 6-8 fx. The Alternaria-form was grown from the ascospores by Halsted and from the Alternaria spores, grown in pure culture, perithecia were obtained in about twelve days. P. albicans Fcl. occurs on chicory as Phoma albicans; P. hyacinthi Sor. on hyacinths with its conidia as Cladosporium fasciculare; P. hesperidearum Cotton, in its conidial form, Spori- desmium pyriforme, causes a black mold on oranges. P. herbarum (Pers.) Rab. (conidia= Macrosporium commune) is a common saprophyte which sometimes becomes parasitic. P. pisi (Sow.) Fcl.^'^ is found on the garden pea; Perithecia and spores as in P. herbarum but spores more narrow. P. ulmi. Fr. causes an elm leaf spot. P. infectoria Fcl. a com- mon saprophyte, parasitizes tobacco. P. oryzae Miy. is on rice; P. negundinis Oud. is injurious to nursery stock of Negundo; P. putrefaciens (Fcl.) Fr. (conidia= Sporidesmium) is on carrots. Pleosporae on grains.^^^' ^'* Several species of Pleospora with their attendant conidial forms of Helminthosporium and Alternaria are known on various grains and grasses. Cross inoculation experiments have shown here biologic specialization similar to that encountered among the Erysiphese, in that conidia or ascospores from one host usually give negative results on host species other than that on which they grew. Thus Diedicke ^''^ says the Pleospora of Bromus cannot be grown on Triticum repens nor on cultivated barley or oats. Helminthosporium was formerly thought to be the conidial stage of all of these grain Pleosporas, but recent work of Diedicke shows that one form which he regards as P. trichostoma (Fr.) Wint. THE FUNGI WHICH CAUSE PLANT DISEASE 261 in- 22 possesses an Alternaria conidial form. Following Diedicke, the forms given below would be recognized. P. bromi Died. Perithecia brown, hairy; asci 189-288 x 34-59 n, saccate, thin- walled; spores 2-seriate, golden-brown, 4-celled, 48-83 x 19-33 /x. Conidia (=Helminthosporium bromi) on brownish spots, 108- 150 X 13-20 n, 5 to 7-celled, dark colored. On Bromus. P. gramineum Died. Conidia (=Helminthosporium gramineum); conidiophores short, subflexuose, light-brown; conidia solitary, elongate-cylindric, 4 to 7-celled, 15-19 p, wide and of variable length. The mycelium invades the tissue causing long brown spots. These later become covered with an abundance of conidiophores which emerge through the stomata. Potter also reports vasion and complete occupation of ovaries by the mycelium. Sclerotia-like bodies are formed on leaves and stems. They were first seen in artificial cul- tures of the fungus by Ravn ^^^ and have been since found in nature (Noack 244). The conidiospores have been shown to be long-lived, and spring infection begins largely from conidia carried over winter on seed. Extensive study was made of the conidial form by Ravn who found the mycelium to be of two kinds, one aerial and hyaline, the other strict and dark. It grew well on acid or neutral media. Careful infection experiments (Ravn) proved the pathogenicity of H. graminum for barley but showed it incapable of infecting oats, rye or wheat. Ravn regards the disease produced by H. gramineum as often general, not local, in that the mycelium may invade the growing points, resulting in infection of all the leaves. Fig. 192.— p. single spore Diedicke. trichostoma. 1, group of iisci at the apex of an ascus. , 2, a After 262 THE FUNGI WHICH CAUSE PLANT DISEASE P. tritici-repentis Died, is found on Triticum repens (=Agropy- ron repens.) Conidia=Helminthosporium tritici repentis. P. trichostoma (Fr.) Wint. ( = Pyrenophora trichostoma (Fr.) Sacc.2^2 Perithecia gregarious, innate, conical, black, ostiole surrounded by black hairs, which are simple, septate, 6-8 ix in circumference ; asci clavate 300 x 40 /x; spores broadly oblong, obtuse, unequally 4 to 6-septate, muriform, brownish, 52 x 20 m; paraphyses branched. On rye with the conidial form =Alternaria trichostoma Died. In the present state of our knowledge little is to be gained by recognition of these purely "biologic species," and all the forms may be grouped under the name P. trichostoma, recognizing the fact that it shows biologic differentiation. Two hypothetical forms P. teres Died, and P. avense Died, pertain to Helminthosporiums of corresponding names. Massariaceae (p. 223) Stroma none; perithecia separate, sunken, not erumpent, open- ing by a small pore, leathery or carbonous, compact; spores usually surrounded by a jelly-like substance; paraphyses present. This family of ten genera and about one hundred twenty-five species contains only one parasite of interest. Key to Genera of Massariaceae Spores 1 -celled Spores not surrounded by a jelly-like sub- stance 1 • Enchnoa. Spores surrounded by a jelly-like sub- stance 2. Pseudomassaria. Spores several-celled Spores not muriform Spores hyaline or yellow Spores ellipsoid to spindle-shaped, several-celled, hyaline 3. Massarina. Spores spindle-formed, curved, 3 to 4- celled, yellow 4. Ophiomassaria. Spores 2 to 4-celled, elongate, hya- line 5. Charrinia, p. 263. THE FUNGI WHICH CAUSE PLANT DISEASE 263 Spores brown Spores 2-cellcd Pefithocia scattered irre}z;ularl\'. . . G. Phorcys. Perithecia in circular clusters 7. Massariovalsa. Spores more than 2-celled Spores ellipsoid to spindle-shaped, many-celled 8. Massaria, p. 263. Spores cylindric, bent, 8-cclled. . . 9. Cladosphaeria. Spores muriform 10. Pleomassaria. Massaria theicola Fetch invades the ducts of the tea plant. The genus Charrinia is said l\v Viala & Ravaz ^'^■' to contain the ascige- rous form of Coniothyrium diplodiella (Speg.) Sacc. Gnomoniaceae (p. 223) Perithecia sunken, with an elongate, cylindric, beak-like ostiole, rarely with a papillate one; leathery or membranous, rarely borne on a stroma; asci mostly thickened apically and opening by a pore; spores hyaline; paraphyses usually absent. A family of about one hundred fifty species; four genera con- tain important pathogens. Key to Genera of Gnomoniaceae Spores l-celled Mouth of the perithccium short Asci cylindric, 8-spored 1. Phomatospora. Asci clavate, 2-8porcd 2. Geminispora. Mouth of the perithccium elongate, beak- like Mouth of the perithccium straight Asci many-sporcd 3. Ditopella, p. 264. Asci 8-spored Spores ellipsoid or fusoid A clypeus present 4. Mamiania. Stroma present 5. Glomerella, p. 264. Stroma absent 6. Gnomoniella, p. 273. Spores elongate fusoid, or filiform 7. Cryptoderis. Mouth of the perithccium recurved. . . 8. Camptosphaeria. 264 THE FUNGI WHICH CAUSE PLANT DISEASE Spores 2 or more-celled Asci 8-spored Spores elongate, 2 to 4-celled 9. Gnomonia, p. 274. Spores fusiform, curved, 2-celled 10. Hendersonia. Asci many-spored; spores elongate, 2-celled Perithecia beaked 11. Rehmiella. Perithecia not beaked 12. Rehmiellopsis, p. 276. Ditopella de Notaris (p. 263) Perithecia corticolous, covered, globose or somewhat depressed, ostiole suberumpent; asci subclavate, polysporous; spores oblong or fusoid, continuous, subhj^aline; paraphyses none. D. ditopa (Fr.) Schr. causes death of oak twigs in Europe; D. fusarispora d. Not., occurs on alder in Europe. Glomerella Spaulding & von Schrenk 2^2. 342 (p 263) Perithecia cespitose, membranous, dark brown, rostrate, of a lighter color at the apex in early stages, flask-shaped, hairy, on or immersed in a stroma; asci sessile, clavate; spores 8, hyaline, oblong, 1-celled, slightly curved, elliptic; paraphyses usually none. Conidia=in part Colletotrichum and Gloeosporium. This genus was first described by Stoneman, from perithecia obtained from cultures of the conidia,^'*'^ as Gnomoniopsis. On ac- count of preoccupation it was renamed Glomerella by Spaulding and von Schrenk ^^^ in 1903. Studies by Shear have shown that there is much variation in pure line cultures both from ascospores and from conidiospores.'^^ This leads to great uncertainty as to spe- cific limitations as will become apparent in the paragraphs below. The conidial forms are very common and are usually parasitic. The ascigerous stages are comparatively rare. Sometimes they are found in nature; again only in artificial culture. Some forms known to be ascigerous may in one culture yield abundant peri- thecia while other cultures of the same fungus may persistently refuse to bear asci at all. G. rufomaculans (Berk.) S. & S.2^259 Perithecia on decaying fruits, subspherical, more or less grouped; THE FUNGI WHICH CAUSE PLANT DISEASE 265 asci subclavate, fugaceous, 55-70 ju; ascospores allantoic!, 12- 22 X 3-5 n; conidial stage ( = Gloeosporium rufomaculans) with small sori, developing in more or less concentric circles, usually soon rupturing and pushing out spores in small pinkish masses; spores hyaline to greenish, chiefly oblong, unicellular 10- 28 X 3.5-7 fjL. The conidial stage of this fungus was first described by Rev. M. J. Berkeley in 1854 as a Septoria. It was later transferred to the form genus Gloeosporium under which name the literature pertaining Fig. 193.— 7. pcrithecium of G. rufomacu- lans showing asci in situ; 6, asci show- to it is largely to be lOUnd. ing detail. After Spaulding and von See Southworth.2^0 The as- ^'^'"°^- cigerous stage was found by Clinton -'"^ in 1902 and the fungus described as a Gnomoniopsis. In 1903, it was given the present name. A bibliography of some one hundred eighty titles is given by Spaulding and von Schrenk.'''^ The conidia germinating on apples send germ tubes through the skin, usually through wounds, occasionally through a sound surface.-'^ The mycelium grows subepidermally, branching rapidly, intercellularly and intracellularly, absorbing the sugar and other nutrients present, and resulting in brown discolora- tion of cells and dissolution of their connec- tion with neighboring cells. The mycelium is first hyaline but later, especially in the Fig. 194.— g. cactorum. stromata, it may be quite dark. Acervuli brg'eTm°?ating'spores'^ ^oou appear, oftcu in conccntric rings, lift- After Spaulding and ing the epidermis with their palisades of von Schrenk. . ,. , rr-M i n i i- conidiophores. Ihe latter, at first hyaline, later olivaceous, bear the numerous conidia, which are pinkish, rarely cream-colored, in mass. In germination the conidia be- come uniseptate and often on the tips of the young mycelium develop the dark thick-walled irregularly shaped spore-like struc- tures, so common on the sporelings of the Melanconiales. These 266 THE FUNGI WHICH CAUSE PLANT DISEASE structures are regarded by Hasselbring ^^^ as organs of attachment to aid in infection, though they doubtless serve other purposes as well. Perithecia of this species were first obtained by Clinton ^^^ who grew them in abundance on artificial media from sowings of coni- diospores taken from pure cultures. The typical Gloeosporium stage was also grown from ascospores. Perithecia were also found in pure cultures on apple agar by Spaulding and von Schrenk. They appeared in black knotted masses of mycelium which were often 4-5 mm. in diameter, the perithecia varying from one to many in each such stroma. The asci were evanescent, disappearing soon after the spores matured. That this fungus is the cause of a limb canker was suggested by Simpson's discovery of the canker in July, 1902 and was definitely proved by Spaulding and von Schrenck,-^* and by Burrill and Blair ^^^ in the same year. In canker forma- tion the mycelium grows in the live bark, killing it and the cambium. The cankers are thought to be comparatively short lived, perhaps surviving only the third year. Reciprocal inoculations between fruit and twigs have proved the fungus in the two cases to be identical. Conidia and ascospores develop on both fruit and twigs. The fungus has been repeatedly grown in pure culture on numer- ous media by many investigators and many inoculations with conidia into both fruit and twigs have proved the causal relation of the fungus to the apple rot and twig canker. Inoculations from ascosporic material have given the same results. That the spores may be insect-borne was shown by Clinton; -'•'^ that they may also travel on the wind was shown by Burrill. -^^ Fig. 195. — G. rufonmculans, Note septa and appressoria. von Schrenk. germinating conidia. After Spaulding and THE FUNGI WPIICH CAUSE PLANT DISEASE 2G7 The mycelium hibernates in hmb cankers and in mummified fruit.25^ It is impossible morphologically to distinguish the conidial stages of manj^ species of Gloeosporium and Colletotrichum grow- ing on a great variety of hosts, and much inoculation work has been done to ascertain the relationships existing between these many forms. Thus the author ^^° in Dr. Halsted's laboratory made inoculations as indicated in Fig. 367. Southworth cross inoculated a Gloeosporium from grape to apple and from apple to grape; Stoneman from quince to apple. -^~ Even such cultures give little evidence of difference between these forms and it usually is impossible to distinguish between the conidial forms on either morphological or biological grounds. Some group under Glomeralla rufomaculans as its conidial forms, what were formerly known as Gloeosporium fructi- genum, G. rufomaculans, G. versicolor and G. Iseticolor. Further studies of the ascig- erous stages have led to con- solidation rather than to seg- regation of species. Thus an ascigerous stage, a Glomer- ella, was obtained in pure culture from the following conidial forms by Shear and Wood: 258 G. rufomaculans from grape, G. fructigenum from apple, G. sps. from cranberry, G. elasticae from Ficus (see p. 544) a Gloeo- sporium from Gleditschia, one from Ginkgo, Colletotrichum gossypii from cotton (see p. 271) and C. lindemuthianum. (See p. 547) from bean. These authors after careful study of these perithecia and cultures conclude that: "in the present state of Fig. 196. — Plate culture of G. rufoniacu- lans showing perithecia-bearing masses. After Spaulding and von Schrenk. 268 THE FUNGI WHICH CAUSE PLANT DISEASE our knowledge, it may be best to regard the various forms we have studied as varieties of one species." Among the hosts of G. rufomaculans may probably be num- bered at least apple, grape, pear, quince, peach, tomato, egg- plant, pepper, sweet pea ^^^ and cherry. -^^ G. rufomaculans var. cyclaminis P. & C.-''^ Perithecia densely gregarious, indefinite, light-colored, around spots, brown, membranous, subglobose or distinctly ros- trate, ostiolate ; asci clavate- cylindric, apex pointed, 50- 65 X 8-9 /*; spores oblong to elliptic, 16-18 x 4-4.5 /x. C o n i d i a ( = Collet otri- chum) ; acervuli amphi- genous, brownish, large; conidia oblong to linear, obovate, straight, or slightly curved, ends round, 12-15 x 4-5 n; conidiophores long, slender; setae free, short, rigid. This variety is reported on greenhouse Cyclamens, causing leaf spotting. Ma- ture perithecia were found on the leaves. Cultures from the ascospores gave a Colletotrichum as the co- nidi al form and a similar Colletotrichum collected from the leaves in pure culture gave the Glomerella. G. cingulata (Atk.) S. & S. Perithecia cespitose, stromate, dark-brown, flask-shaped, mem- branous, 250-320 X 150 fj., shortly rostrate, more or less hairy; asci clavate, 64-16 /*; spores hyaline, elliptic, slightly curved, 20-28 X 5-7 fx. Conidia (=Gloeosporium cingulatum); acervuli 100-150 ijl, rupturing the epidermis, in age black; conidiophores numerous. Fig. 197. — G. rufomaculans. Pustules on apple, enlarged. After Spaulding and von Schrenk. THE FUNGI WHICH CAUSE PLANT DISEASE 209 crowded, simple, hyaline; conidia oblong to elliptic, straight or curved, basally pointed, 10-20 x 5-7 n. This was first described in conidial form as a GlcEosporium by Atkinson "^° on privet as cause of cankers. The fungus was isolated and gro^\^l in pure culture. Later perithecia were obtained in the pure cultures.^'*^ G. piperata (E. & E.) S. & S. Perithecia cespitose, thinly membranous, dark-brown, pyriform, hairy; asci clavate; spores slightly curved, elUptic, 12-18 x 4-6 /i. Fig. 198. — Diagrammatic section through acervulus of G. rufomaculans. a, parenchyma, h, cuticle, c, subhymenial fungous layer, d, conidiophores, e, spores, 6, conidiophores and conidia in detail. After Clinton. Conidia (=Gloeosporium piperatum) on circular or oval spots; acervuli pustular, concentrically arranged, conidia 12-23 x 5-6 ^t.^^^ The ascigerous stage was grown from pure cultures of the conidia taken from pepper by Miss Stoneman ^'*" the perithecia appearing about a month after inoculation. Typical conidia were also se- cured from ascospore sowings. G. cincta. (B. & C.) S. & S.-^ Perithecia 180-280 /z, flask-shaped, membranous, cespitose; asci clavate, truncate or obtuse, 65-70 yn; spores elliptic, curved, 5-20 X 3 M-''^ Acervuh erumpent; conidia (=Colletotrichum cinctum) 12-15 x 270 THE FUNGI WHICH CAUSE PLANT DISEASE 3-4 n, elliptic, guttulate; set£e present, but almost obscured by the spore mass. The ascigerous stage was demonstrated by Stoneman '^'^ from pure culture studies. The conidial stage was described by Hal- sted ~^^ as the cause of a blighting of orchid leaves (Sobralia) in New Jersey. Various hosts are orchids, Sarracenia, rubber plant, Dracaena "^ and Anthurium.-^- Fig. 199. — G. rufoniaculans, acervulus showing conidia, conidiophores and setae. After Hasselbring. G. rubicola (Ston.) S. & S. Perithecia quite similar to those of G. piperata and G. cinta but lacking the apical tuft of hair and rather larger in size. Conidia (=Colletotrichum rubicolum) forming large, dark- brown patches on the upper surface of the leaf; sori small, dark, suberumpent; conidia oblong, elliptic, 12.5 x 6 /i. The conidial form on red raspberry was shown by Stoneman ^'^^ by pure culture studies to possess this ascigerous stage. G. psidii (Del.) Shel.-*''''-26^ Perithecia 200-300 n, spherical, rarely distinctly beaked; asci THE FUNGI WHICH CAUSE PLANT DISEASE 271 cylindric to broadly clavate, blunt, 45-55 x 9-10 ^l^, spores curved, continuous, granular, 13-15 x 5-6 /z. Conidia ( = (!loeosporium psidii), acervuli subepidermal on defi- nite spots, 90-120 fj.; conidiophores hyaline, cylindric, 15-18 x 4-5 ju; conidia elliptic, oval, hyaline, 10-13 x 4-6 /i. Artificial culture studies by Sheldon -^^' -^^ demonstrated the ascigerous stage. Extensive study was made of the growth on Fig. 200. — G. piperata, 99, perithecium external and in sec- tion. 100, asci in detail. After Stoneman. apple-agar, apples, plums, etc. Two distinct forms of conidia were observed, one on loose hypha?, the other in acervuli. The species should probably be regarded as a variety of G. rufo- maculans. It occurs on the guave. G. gossypii (South.) Edg. Perithecia distinct or crowded, very abundant, covered, dark brown to black, subglobose to pyriform, 80-120 x 100-160 /i, beak up to 60 n long; asci numerous, clavate, 55-70 x 10-14 n; 272 THE FUNGI WHICH CAUSE PLANT DISEASE spores elliptic, hyaline, rarely curved, 12-20 x 5-8 n; paraphyses long and slender, very abundant. Conidia ( = Colletotrichum gossypii), acervuli erumpent, coni- diophores colorless, longer than the spores, 12-28 x 5 fx; conidia irregularly oblong, hyaline or flesh-colored in mass; setse single or tufted, dark at base, colorless above, straight, rarely branched. The conidial stage of this fungus was de- scribed by Southworth ^^^' ^"^ and independ- ently by Atkinson -^^' ^^^' ^'-^ on cotton. The ascigerous stage was first seen by Shear & Wood ^^^ in artificial culture and by them regarded as probably a variety of G. rufomaculans. Since these studies Edger- ton -^ from examination of perithecia de- veloped naturally in the open, has proposed it as a separate species. The mycelium is richly branched and sep- tate, usually hyaline but sometimes slightly Fig. 201.— G. gossypii. smoky. It grows between and in the host Section of young boll, cells which are often filled with it, causing showing the fungus r i i in j i penetrating the hull collapse, loss of chlorophyll, and brownmg. ySung'^sled.'^Spores Studies by Atkinson and by Barre ^^^ show are being produced ^^^t in case of diseased bolls the mycelium upon the outer por- tion of the hull and may extend through the pericarp, sporing on upon the surface of .. . ,, . i .1 j. j.i, i the young seed coat, its mner Wall; extend thence to the seeds; After Barre. penetrate and grow in them. Fig. 201, and in the cells of the lint. Barre has shoAAm that even the endosperm and cotyledons may be invaded, Fig. 201, and spores produced upon them while \\dthin the seed coats. Such seeds and lint may appear outwardly as though perfectly normal. The conidia are formed in acervuli, subtended by stromata. Setae, from few to many increasing with age of the acervulus, are present and conidia are occasionally found on them. In ger- mination conidia usually develop one, sometimes two septa and produce dark chlamydospores. Acervuli are common on bolls, less so and smaller on leaves and stems. ' The perithecia as found in the field by Edgerton in Louisiana THE FUNGI WHICH CAUSE PLANT DISEASE 273 were usually entirely embedded, with the beaks only protruding and were often numerous and crowded. Cultural evidence that Edgerton's specimens were actually genetically connected with the cotton anthracnose are wanting. The fungus has been repeatedly studied in pure culture and numerous inoculations have thoroughly proved its pathogenicity, the disease usually showing within a few days after inoculation, though sometimes incubation is delayed much longer. Infection of stems is often at a wound such as a leaf scar; or on leaves at some point of weakness. Cotyledons and young plants are especially susceptible. On bolls infection is common at the line Fig. 202.— G. gossypii, D, and E, fun- of dehiscence of the carpels. Ac- ^l^^Baire '"^ ''°"°° "°* ^^^'^' cording to Barre, there is evidence that the fungus may destroy the contents of the boll before it shows upon the outside. Barre showed that 44% of flowers that received spores within ten hours after opening produced dis- eased bolls; but inoculations by spraying produced no results on bolls after they were three-fourths grown. Seed from a field that bore 35% infected bolls gave on germina- tion, 12% of infected seedlings, the disease appearing upon cotyle- dons or hypocotyls even before they unfolded. Atkinson ^^° found that conidia five months old were alive, but that at seven months they failed to germinate. Barre also found the conidia and the mycelium of the fungus to be comparatively short lived. G. atrocarpi Del. on Atrocarpus leaves has been described as a perfect stage of Gloeosporium atrocarpi Del. A fungus on Cattleya ^^' ^^^ described by Maublanc & Lasnier as a Physalospora should perhaps be considered as a Glomerella. Gnomoniella Saccardo (p. 263) Perithecia sunken and usually remaining so, with a long cylin- dric, erumpent ostiole, leathery, black; asci ellipsoid or fusoid, 274 THE FUNGI WHICH CAUSE PLANT DISEASE Fig. 203.— G. tubifor- mis, perithecia. After Winter. apically thickened and opening by a pore; spore elliptic, 1-celled, hyaline; paraphyses none. This genus of some twenty-five species contains G. tubiformis (Tode) Sacc. which is said to be the ascigerous stage of Lepto- thyrium alneum Sacc. growing on Alder. Two other species, G. fimbriata and G. coryli are found on hornbeam and hazel respectively. Gnomonia Cesati & de Notaris (p. 264) Perithecia covered, or erumpent, submembranous, glabrous, ostiole more or less elongate; asci ellipsoid or fusoid, apically thick- ened, opening by a pore; spores elongate, hyaline, 2 to 4-celled; paraphyses none. There are some sixty species. Fusicoccum, Myxosporium, Sporo- nema, Gloeosporium, Marssonia, Asteroma, Leptothyrium occur in some species as the conidial form. The ascigerous form usually follows as a saprophyte after the parasitic conidial stage. G. veneta (Sacc. & Speg.) Kleb.^^^^ s'^^, 323, 335 Perithecia immersed, subglobose or slightly flattened, 150- 200 fi, short, rostrate; asci long-clavate, 48-60 x 12-15 /x, gen- erally bent at right angles at the base, apically very thick, opening by a pore; spores 14-19 x 4-5, straight or slightly curved, unequally 2-celled, the upper cell longer. Conidia variable in habitat, and habit. (1) ( = Gloeosporium nervise- quum) acervuli subcuticular 100- 300 />; conidiophores short, conidia oozing out in a creamy-white mass, hyaline, ellipsoid, 10-14 x 4-6 /x, pointed at one end and rounded at the other. (2) ( =G. platani) acervuli sub- epidermal, conidiophores long; conidia as above. (3) ( =Discula platani = Myxosporium valsoideum) form- ing minute, subepidermal, erumpent pustules on twigs; conidia elliptic to oblong, hyaline, 8-14 x 4-6 /x; (4) ( =Sporonema platani Fig. 204. — G. veneta, perithe- cium. After Edgerton. THE FUNGI WHICH CAUSE PLANT DISEASE 275 = Fuscicoccum veronense). Pycnidia formed on old leaves on the ground, crumpent, subcuticular, brown, 200-300 ju; conidia numerous, oblong, ovoid to f usoid, 7-1 1 x 3-4 /x. The conidial form on sycamore and oak, first described in 1848, is common on leaves and young branches, the mycelium checking the sap-flow and causing death of surround- ing tissue. A stroma is formed on the outer layers of the mesophyll and from this arise the short conidiophores to constitute the acervulus. Infection experiments by Tavel -^^ gave negative results. Other infection experiments have also been unsatisfactory. The ascigerous form was first found by Klebahn ^'^ on old leaves on which it ma- '^^^J spores.^ After' Ed- tured about Christmas time. While the co- gerton. nidia are uniform in shape four modes of development are found, as stated above. Pure cultures from all the spore forms were compared by Edger- ton ^~- confirming Klebahn's conclusion as to their identity. Cul- tures by Stoneman -^^ showed the forms on sycamore and oak to be the same. G. leptostyla (Fr.) Ces. & d. Not. Perithecia conic, short-beaked; asci subclavate, 45-65 x 10-12 ju; spores f usoid, curved, 18-22 x 4 /i, hyaline. Conidial phase (=Marssonia juglandis). Acervuli gregarious, hypophyllous, rounded; conidia obovoid, 8-10 x 4-5 n, 1-septate, pointed above, truncate below, greenish. The connection between the conidial and ascigerous forms was demonstrated by Klebahn ^^^ by pure cultures and by ascosporic infection. The conidial form is common on walnut leaves; espe- cially severe on the butter-nut (Juglans cinerea) often defoliating this host in mid-summer. G. quercus-ilicis Berl. occurs on oak leaves in Italy. G. erythrostoma Auer. is the cause of a disease of cherry leaves in Europe; -'*'' '■^■''^ G. padicola Kleb. is the ascigerous stage of Asteroma padi which is widely distributed in Europe on Prunus. 276 THE FUNGI WHICH CAUSE PLANT DISEASE G. oryzae Miy. occurs on rice.'^'^ G. rubi Rehm may occasionally cause disease of blackberry canes.-'* Rehmiellopsis Bubak & Kabat (p. 264) Similar to Rehmiella except that the perithecia are not beaked and the pycnidia do not have a definite opening. R. bohemica Bub. & Kab.; (conidia=Phoma bohemica)^*^ oc- curs as a parasite on fir needles. Clypeosphaeriaceae (p. 223) Perithecia immersed, astromatic or with a pseudostroma built of hyphse which, with the adjacent substratum, forms a thin cly- peus that is usually evident only above; ostiole short to long- beaked, erumpent, walls mostly carbonous to membranous; paraphyses usually present. A small family chiefly saprophytes. Key to Genera of Clypeosphaeriaceae Spores 1-celled Perithecia soft-membranous, spores hya- line or brown 1. Trabutia. Perithecia leathery; spores brown 2. Anthostomella, p. 276. Spores more than one-celled Spores with cross walls only Spores cylindric, ellipsoid or fusiform Spores hyaline, 1 to 3-septate 3. Hypospila. Spores brown Spores elongate 4. Clypeosphaeria. Spores fusiform, more than 4- septate, sometimes muriform. 5. Phaeopeltosphaeria. Spores filiform, hyaline to yellow 6. Linospora. Spores muriform Spores ovate, brown 7. Peltosphaeria. Spores short, fusiform, hyaline 8. Isothea. Anthostomella Saccardo Mycelium fusing with the upper surface of the substratum to form a thin, black, rounded pseudostroma; perithecia sunken, sub- THE FUNGI WHICH CAUSE PLANT DISEASE 277 globose, with a short, conical ostiolc, walls black, carbonous to leathery; asci cylindric, 8-spored; spores elliptic, continuous, brown, unappendaged ; paraphyses usually present. Over one hundred species, chiefly sapro- phytes. A. sullae Montem. occurs as the cause of a leaf spot on sulla.-^^ A. bohiensis (Hmp.) Speg. is on cacao; A. destruens Sh. on cranberry; A. coflfeae Desm. on coffee. ^^^' '^^ Fig. 206.— A. des- truens. 8, pcrithe- cium; 9, ascus; 10, spores; 11, germi- nating spore. After Shear. Valsaceae (p. 223) Stroma effused, subglobose, conic, or pulvinate, often indefinite; perithecia sunken in the stroma, scattered or clustered, black, leathery; asci cylindric or clavate; paraphyses usually present. Over one thousand species, chiefly saprophytic. Conidia are present on hyphse or in pycnidia. Key to Genera op Valsaceae Spores 1-celIed Spores cylindric or ellipsoid, with a brown membrane I. Anthostoma. Spores ellipsoid, curved or not, with a hyaline membrane 2. Valsa, p. 278. Spores more than I-celled Spores with cross walls only Spores hyaline Spores unappendaged Spores ellipsoid or fusoid 2 to 4- celled 3. Diaporthe, p. 278. Spores elongate, fusoid, constricted in the middle 4. Vialaea. Spores appendaged, I appendage at each end and 2 or 3 in the mid- dle 5. Caudospora. Spores brown Spores 2-cellcd, ellipsoid 6. Rhynchostoma. Spores many-celled, fusoid 7. Kalmusia. 278 THE FUNGI WHICH CAUSE PLANT DISEASE Fiu. 207. — Valsa. A, habit sketch; B, perithecia; C. asci. After Tulasne. Spores muriform Stroma effused Spores hyaline 8. Thyridella. Spores colored 9. Thyridium. Stroma none or pulvinate 10. Fenestella. Valsa Fries (p. 277) Perithecia on a more or less definite stroma, immersed, the ostiole erumpent, black, firm; asci globose to cylindric, often long-pedunculate; spores 1 -celled, rarely 2-celled, cylindric, rounded, hya- line or light-brown; pa- raphyses none. V. leucostoma (Pers.) tp 22, 229, 280 Stroma strongly con- vex, 2-3 mm., whitish and granular within, outer layer coriaceous; perithecia immersed; asci fusoid-clavate, subsessile, 35-45 x 7-8 /x; spores biseriate, allantoid, hyaline, slightly curved, 9-12 x 2-2.5 n. Conidia ( = Cytospora rubescens); stromate, erumpent, reddish; conidia allantoid, 4 fi. On pome and stone fruits throughout Europe, Australia and America causing the disease known as " dieback." The fungus was studied by Rolfs -"^' ^^^ who worked out its life cycle. V. oxystoma Rehm. occurs on Alnus in Europe; V. (Eutypa) caulivora Rehm. affects Hevea. V. ambiens Fr. is on the apple in Europe. V. (Eutypella) prunastri (Pers.) Fr. is the cause of serious dis- eases of apples, plums, etc., in England. V. (Eutypa) erumpens Mas. is reported as a wound parasite in the tropics on Ficus, and cacao. Diaporthe Nitschke (p. 277) Stroma very variable, usually definite; perithecia membranous subcoriaceous, generally pale-cinereous within, with a cylindric or filiform beak; asci fusoid; spores fusoid to subelliptic, 2-celled, THE FUNGI WHICH CAUSE PLANT DISEASE 279 hyaline, appendaged or not; pa- raphyses none. Conidia=Phoma, Cytospora, etc. D. taleola (Fr.) Sacc. Stroma cortical, definite, de- pressed, pulvinate, 2-4 mm., cov- ered; perithecia few, 4-10, buried, their ostioles converging, erumpent in a small light-colored disk; asci cylindric, 120-140 x 10-12 n, spores elliptic, uniseptate, constricted, with setaceous appendages, 15-22 x 8-9 (ji. It causes canker on oak, killing the cortex over large areas. A year later the cushion-like stromata appear. The mycelium penetrates both wood and bark, probably enter- ing through wounds. D. albocarnis E. & E. on Cornus is destructive. D. ambigua and D. sarmentella are on pear and hop, D. stru- mella on a wide range of hosts, in conidial form as Phoma. Fig. 208.— Diaporthe. in section; C, asci. lasne. o B, stroma, After Tu- Melanconidaceae (p. 223) A small family of less than two hundred species contains only four parasitic genera. Stroma pulvinate, sunken; perithecia sunken in the stroma, the mouth erumpent; asci cylindric or clavate; paraphyses present. Key to the Genera of Melanconidaceae Spores 1 -celled, hyaline Spores ellipsoid or short-fusiform I. Cryptosporella, p. 280. Spores elongate-cylindric, curved 2. Cryptospora. Spores 2-celled Spores hyaline Conidia in pyenidia; 1-cellcd, hyaline. . 3. Valsaria. Conidia not in pyenidia, dark brown. . 4. Melanconis, p. 281. Spores brown 5. Melanconiella. 280 THE FUNGI WHICH CAUSE PLANT DISEASE Spores more than 2-celled Spores hyaline Spores elongate, multicellular 6. Calospora, p. 280. Spores fusiform, multicellular 7. Holstiella. Spores brown Spores elongate, multicellular; asci 8 or 4-spored 8. Pseudovalsa, p. 281. Spores long-cylindric, very large, asci l-spored 9. Titania. Calospora Saccardo One species, C. vanillae Mas., reported as causing a Vanilla trouble,^^ is perhaps identical with Gloeosporium vanillae C. & M. Cryptosporella Tulasne (p. 279) Stroma valsoid, pustuliform, covered; perithecia embedded, subcircinate, with converging necks united in an erumpent disk; asci cylindric to globoid; spores elongate, cyHndric, hyaline, 1-celled. C. anomala (Pk.) Sacc^^^- -«^ Pustules prominent, 2-5 mm., erumpent; penetrating the wood and generally having a thin black crust beneath them, disk convex or slightly depressed, cinereous to black ; perithecia crowded, deeply em- bedded in the stroma, often elon- gate, ostioles scattered, black; asci short, broad, fugaceous; spores hya- line, elliptic, simple, 7-8 /i. Common on hazel and filbert in America, causing the destruction of the tops while the roots re- main alive. C. viticola Sh.324 Pycnidia (=Fusicoccum) with labyrinthiform chambers, ostiolate but frequently rupturing. Spores hyaline, continuous, of two forms in the same cavity. 1. Subfusoid, 7.5 x 2-5 fi. 2. Long, slender, curved, 18-30 x 1-1.5 /x. Perithecia buried in irregular pulvinate Fig. 209. — C. anomala. 31, stroma and perithecia; 32, an ascus; 33, spores. After Humphrey. THE FUNGI WHICH CAUSE PLANT DISEASE 281 stromata, beak exserted; asci 60-72 x 7-8 /x; paraphyses slender, septate, wavy; ascospores subelliptic, hyaline, continuous, 11-15 x 4-6 tx. Fig. 210. The conidial stage was described by Reddick as the cause of necrosis of grape vines ^^^ though he has since stated that the amount of damage due to this disease is not so great as at first thought. The ascigerous form in pure culture in the hands of Shear ^^^ gave rise to the typical conidial form, identical with that grown from pure cultures of the pycnospores. Melanconis Tulasne (p. 279) Stroma valsoid, seated in the substratum, partially orumpent; perithecia clavate, immersed, with long cylindric beak; asci cjdin- dric, long-clavate, 8-spored; spores ellipsoid to elongate, hyaline. About twenty species; chiefly saprophytes. M. modonia Tul. in its conidial form (=Fusicoccum pernicio- sum) causes a serious disease of the chestnut in Europe.^^^' ^^^ Pseudovalsa longipes (Tul.) Sacc. is parasitic on oak. Diatrypaceae (p. 223) Stroma effused or pulvinate, built of thick hyphae, under the peridium, at length prumpent, bearing both asci and conidia or present only with the conidia; perithecia sunken in the stroma or superficial, ostiolate; asci usually thickened apically; 4 to 8 or many-spored; spores usually continuous, small, cylindric, curved. About one hundred seventy-five species. One parasitic genus occurs on cherry and plum. Key to Tribes and Genera of Diatrypaceae Stroma absent from ascosporic stage I. Calosphaerieae. Asci 8 (rarely 4)-spored Spores 1-celled 1. Calosphaeria, p. 282. Spores 2-celled 2. Cacosphaeria. Asci many-spored 3. Coronophora. Stroma present in the ascosporic stage II. Diatrypeae. 282 THE FUNGI WHICH CAUSE PLANT DISEASE CalosphaBria. Tulasne (p» 281) Perithecia astromate, free or on the inner bark, scattered or clustered, ostiole more or less elongate; asci clavate, fasciculate; spores small, cylindric, curved, hyaline, continuous; paraphyses longer than the asci, stout lanceolate, evanescent. About thirty-five species chiefly saprophytes. C. princeps Tul. Perithecia on the inner bark in orbicular or elliptic groups, gen- erally densely crowded, globose, smooth and shining, necks long, Fig. 210.— Crypto- sporella viticola. Asci and pa- raphyses. After Shear. Fig. 211. — Calosphajria princeps. A, group of perithecia; B, conidial stroma. After Tu- lasne. decumbent, flexuose, cylindric, erumpent; asci 12-26 x 4 )u, spores 5-6 x 1-5 yu. On plum, cherry, peach and even pomaceous trees. Melogrammataceae (p. 223) Stroma usually pulvinate, rarely effused, hemispheric, sub- peridial then erumpent and more or less superficial; perithecia sunken in the stroma; conidia occur in acervuli on the surface of the young stromata, or in pycnidia. A small family of about one hundred twenty-five species, only one genus of which contains important pathogens. THE FUNGI WHICH CAUSE PLANT DISEASE 283 Key to Genera of Melogrammataceae Spores 1 -celled Spores roundish ellipsoid, asci long fusi- form 1. Gibelia. Spores ellipsoid or ovate, asci clavate. ... 2. Botryosphaeria, p. 283. Spores 2 or more-celled Spores with cross walls only Spores 2-celled Spores hyaline Paraphyses present 3. Endothia. Paraphyses absent 4. Myrmaeciella. Spores brown 5. Myrmaecium. Spores more than 2-celled, eUipsoid to filiform Spores hyaline many-celled 6. Sillia. Spores hyaline 3-celled 7. Melanops, p. 284. Spores brown 8. Melogramma, p. 284. Spores muriform 9. Berlesiella. Botryosphaeria Cesati & de Notaris Stroma pulvinate, black; perithecia at first sunken in the stroma, remaining so or becoming more or less prominent, usually small, globose, os- tiole inconspicuous, papilli- form; asci clavate; spores elliptic to oval, hyaline, continuous; paraphyses present. B. ribis G. &. Dug.^s^ Stromata black, more or less pulvinate, outer sur- ^^ face botryose, 1-4 mm. in rliomQ+/^T. noiioUir O Q tvitvi ^^g- 212. — Botryosphferia. B. stroma in sec- Uiameter, USUany Z-6 mm., ^ion; C, part of pcrithecium and pycnidium and surrounded by the in section. After Tulasne. fissured periderm, regularly scattered or in more or less definite, longitudinal rows or elongated stromata. Perithecia somewhat 284 THE FUNGI WHICH CAUSE PLANT DISEASE top-shaped, with papillate ostioles and usually projecting, some- times practically superficial. Few to many in a stroma and usually interspersed among pycnidia; 175-250 jx in width. Asci clavate, 80-120 X 17-20 IX, and with numerous filiform paraphyses. Spores fusoid, continuous, hyaline, 16-23 x 5-7 y.. Pycnidia of the compound stylosporic form, Dothiorella, are borne m the same or similar stromata; spores fusoid, continuous, hyaline, 18-31 X 4.5-8 )U. Pycnidia of the simple stylosporic form, Macro- phoma, are embedded in the outer bark under the much-raised primary cortex of young shoots, depressed globular, 175-250 mm. wide; spores fusoid, hyaUne, continuous, 16-25 x 4.5-7.5 n. The cause of a blight of canes of currants. The fungus was first noted in sterile form by Fairchild.-^^ Its history was first fully worked out by Grossenbacher & Duggar.^^^ Extensive inoculation experiments and pure culture studies de- finitely established its pathogenicity. B. dothidae Ces. & d. Not. causes epidemics of disease among cultivated roses. B. gregaria Sacc. is injurious on ^villows in Europe.^^^ Melanops Fuckel (p. 283) Stroma lens-shaped, black; perithecia sunken; asci elongate, 8-spored; spores elongate, 3-celled, hyaline; paraphyses elongate, brown. According to Shear, ^^^ the conidial stage of some members of this genus is a Sphseropsis which is indistinguishable from S. vitic- ola and S. malorum. Melogramma henriquetii Br. & Cav. is parasitic on cork oak. Xylariaceae (p. 224) Stroma variable, usually free but often more or less sunken in the matrix, either upright and often branched or horizontal, ef- fused, crustaceous, pulvinate, globose or hemispheric, black or becoming black, usually woody or carbonous; perithecia periph- eral, immersed, leathery or carbonous, black; asci cylindric or cylindric-clavate, 8-spored; spores continuous, brown or black, fusiform or ellipsoid, paraphyses present or absent. A family of over five hundred species. THE FUNGI WHICH CAUSE PLANT DISEASE 285 Key to Genera of Xylariaceae Stroma encrusted, shield-form, globose or hemispheric, without a sterile base. ... I. Hypoxyleae. Conidial layer beneath the surface of the stroma, erumpent 1. Nummularia, p. 285. Conidial layer free from the first Stroma encrusted Spores 1-cellcd 2. Bolinia. Spores 2-ceIled 3. Camarops. Stroma discoid to hemispheric, en- crusted together Young stroma fleshy, covered by conidia, at length carbonous ... 4. Ustulina, p. 286. Stroma carbonous or woody from the first Stroma without concentric layers. 5. Hypoxylon. Stroma with concentric layers .... 6. Daldinia. Stroma erect, simple or branched, clavate or cylindric, with a sterile base II. Xylarieae. Most of these genera are saprophytic on wood or bark. Nummularia Tulasne Stroma orbicular, cupulate or discoid, becoming black, mar- ginate; perithecia monostichous, peripheral, immersed; asci cy- lindric; spores subelliptic, continuous, dark. The genus contains forty species. Only one is recorded as injurious. N. discreta (Schw.) Tul. Stroma erumpent, orbicular, 2-4 mm., cupulate, with a thick raised margin; ovate, cylindric, nearly 1 mm. long, abruptly con- tracted above into a short neck; asci 110-120 x 10-12 ju; spores subglobose, nearly hyaline, then opaque, 10-12 n; paraphyses filiform. This fungus is usually a saprophyte but has been reported by Hasselbring as a serious parasite on the apple in Illinois. ^^ The mycelium grows more rapidly in the wood than in the bark, 286 THE FUNGI WHICH CAUSE PLANT DISEASE attacking first the parenchyma cells and medullary rays. The young stromata appear under the bark bearing when young small unicellular conidia. The stromata later turn hard and black and D Figs. 213-214. — N. discreta, B, stroma and perithecia, C, a perithecium, D. asci and spores. After Hasselbring. in the upper layers bear numerous flask-shaped perithecia with long necks, Figs. 213-214. Ustulina Tulasne (p. 285) Stroma superficial, subeffuse, rather thick, determinate, at first clothed with a pulverulent cinereous conidial hymenium, finally rigid, carbonous, black, bare and generally more or less hollow; THE FUNGI WHICH CAUSE PLANT DISEASE 287 perithecia immersed, large, papillate-ostiolate; asci pedicellate, 8-spored; spores ovoid-fusiform; paraphyses present. A genus of about ten species, chiefly saprophytes. U. zonata Lev. is the cause of the commonest root disease of tea and is common also on Hevea. BIBLIOGRAPHY OF ASCOMYCETES* 1 Harper, R. A., Ann. Bot. U: 321, 1900. 2 Clausen, P., Bot. Zeit. 63: 1905. ^ Harper, R. A., Carnegie Inst. Pub., Oct. 1905. * Roze, E., C. R. Acad. Sc. Paris, 125: 780. 8 Radais, M., Bot. Gaz. 28: 65, 1899. 6 Peglion v., C. Bak. 7: 754, 1901. ' Lewis, C. E., Me. B. 178: 1910. 8 Atkinson, G. F., N. Y. (Cornell) B. 73: 1894. ' Sadebeck, Jahrb. Hamburg Wiss. Anst. 1: 1884, 8: 1890 and 10: 1891. " Giesenhagen, Flora, 81: 267, 1895. 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B. 36: 858, 1897. " Chester, F. C, Del. R. 3: 81, 1890. " Voges, E., Zeit. 21: 107, 1911. " Muller-Thurgau, C. Bak. 10: 8, 1903. " Dudley, W. R., N. Y. (Cornell) B. 15: 196, 1889. « Stewart, F. C, N. Y. (Geneva) B. 199: 64, 1901. " Klebahn, H., Zeit. 16: 65, 1906. «8 Scribner, F. L., U. S. D. Ag. R. 357, 1888. " Atkinson, G. F., So. 30: 452, 1909. "' Atkinson, G. F., Garden & Forest, 10: 73, 1897. 8' Schwartz, Erkrank. Kicfern durch Cenangium ahietis; Jena, 1895. •2 Ludwig, F., Cent. Bak. 2: 521, 1887 and 3; 633, 1888. «' Hennings, Zeit. 4: 266, 1894. " Durand, E. J., Ann. Myc. 6: 463, 1908. « Brizi, U., Bull. Uffic. Minist. Agricol. Ind. e. Comm. 1903. 8«Tubeuf, Bot. Cent. 21: 1885; 61: 1895. <" Tubeuf, Zeit. f. L. u. F. 408, 1910. «« Eidam, Cohns Beitrage, 267, 1883. 8«Dale, E., Ann. Bot. 17: 571, 1903. ™ Dale, E., Ann. Myc. 7; 215, 1909. 290 THE FUNGI WHICH CAUSE PLANT DISEASE " Fraser, H. C. & Chambers, C. H. S., Ann. Myc. 5: 423, 1907. "Zopf, W., Zeit. 1:12, 1891. " Gilbert, W. W., B. P. I. B. 158: 1909. ■'^ Clinton, G. P., Conn. State, R 15: 166, 1891. " Bull. Inst. Bot. Buitenzorg 4: 19, 1890. ™ Holm, Th., B. P. I. B. 120. " Halsted, B. D., N. J. R. 517, 526, 1903. '8 Lawrence, W. H., Wash. B. 70. " Smith, Grant, Bot. Gaz. 29: 153, 1900. 80 Neger, F. W., Flora 90: 221, 1902. 81 Neger, F., Flora 88: 333, 1901. 82 Harper, R. A., Ber. d. deut. Bot. Gaz. 13: 475, 1895. 83 Harper, R. A., Jahr. f. wiss. Bot. 29: 656, 1896. 8^ Harper, R. A., Carnegie Inst. Pub. 37: 1905. 85 Salmon, Ann. Myc. 2: 70, 1904. 88 Salmon, Bot. Cent. U: 261, 1903. 87 Reed, Geo. M., Bui. Torrey Bot. Club. 36: 353, 1909. 88 Arthur, J. C, N. Y. (Geneva) R. 5: 291, 1886. 89 Humphrey, J. E., Mass.. State R. 10: 239, 1892. 8« Salmon, E., Zeit. 11: 76, 1901. 91 Salmon, E., Tr. Ag. So. 2: 327, 1907. 92 Bailey, L. H., N. Y. (Cornell) B. 7^: 381, 1894. 93 Halsted, B. D., N. J. R. 13: 281, 1892. 94 Halsted, B. D., U. S. D. Ag. R. 376, 1887. 95 Mass. R. 10: 240, 1892. 99 Mass. R. 10: 252, (1892), 1893. 97 Halsted, B. D., N. J. R. U: 357, 1893. 98 Salmon, p.. New Phytologist, 3: 109, 1904. 99 Reed, G. M., Univ. of Wis. B. 250, 1908. i™ Wolff, Beitr. zur Kennt d. Schm.— pilze. 1875. 1" Marchal, C. R. 135: 210, 1902. 102 Salmon, Beih. Bot. Cent. 14: 261, 1903. 103 U. S. D. Ag. R. 105, 1886. 10" Galloway, B. T., Bot. Gaz. 20: 486, 1895. 105 Bioletti, Cal. B. 186: 1907. 106 Riv. d. vit. 655: 9. 107 Couderc, G., C. R. 116: 210, 1893. 108 Pammel, L. H., Iowa, B. 13: 921, 1891. 109 U. S. Dept. Agric. R. 352, 1888. 110 Salmon, E. S., Mon. Torr. CI. 9: 36, 1910. 111 Vanha, J., Zeit. U: 178, 1904. BIBLIOGRAPHY OF ASCOMYCETES 291 "2 Eriksson, J., Bot. Cent. 26: 335, 1886. "3 Fawcett, H. S., Fla. R. 40: 1909. '"Palla, Ber. d. deut. Bot. Ges. 17: 64, 1899. "^ Farlow, W. G., Bull. Buss. Inst., 404, 1876. "« Swingle, W. T. & Webber, H. J., V. P. P. B. 8: 25, 896. '" Webber, 11. J., V. P. P. B. 13: 1897. "8 Fawcett, H. S. & Rolfs P. H., Fla. B. 94. 1" Fawcett, H. S., Univ. of Fla. Spec. Studies 1: 1908. i^oSeaver, F. J., Mycologia 1: 41, 1909, 177. 1-1 Aderhold & Ruhland, Arb. a. d. Biol. Abt. f. Land. u. Forst am Kais. Gesund. 4: 429, 1905. 1" Idem, 3: 48, 1909-1910. 1" Berlese, A. N., Riv. d. Pat. Veg. 5: 88, 1897. 12" Boeuf, F., B. d. Dir. d. L'Ag. et d. Comm. Tunis, 27: 1903, also 1905. 1" Paddock, W., N. Y. (Geneva) B. 163: 204, 1899. 128 Durand, E. J., N. Y. (Cornell) B. 125: 1897. 1" Grossenbacher, J. G., & Duggar, B. M., N. Y. (Geneva) T. B. 18: 1911. 128 Mayer, H., Unt. forst bot. Inst. Munchen 3: 1, 1883. 129 Halsted, B. D., N. J. R. 12: 281, 1891; and 359, 1894. "0 Massee, Kew Bui. Jan. and Feb., 1899. "1 Ihssen, G., C. Bak. 27: 48, May, 1910. "2 Smith, E. F., B. V. P. P. 17: 1899. 1" Higgins, B. B., Sc. 31: 916, 1910. "" Higgins, B. B., N. C. R. 32: 100, 1910. 1" Butler, Mem. Dept. Agric. India, Bot. Ser. 2: 9, 1910. "« Zimmermann, A., C. Bak. 8: 148. 1" Fetch, T., Circ. & Ag. Jour. Roy. Bot. Gard. Ceylon, Nov., 1910. 138 Selby, A. D. and Manns, T. F., Ohio B. 203. "3 Selby, A. D., Ohio B. ,97: 40, 1898. i^oSorakin, N., Zeit. 1: 238, 1891. "1 Cavara, Zeit. 3: 16, 1893. 1*2 Noack, F., Zeit. 10: 327, 1900. 1" Fetch, T., Circ. & Ag. J. Roy. Bot. Gard. Ceylon, 8: 65, 1910. "" Frank, Ber. deut. Bot. Ges. 1: 58, 1883. i« Atkinson, G. F., J. Myc. 11: 248, 1905. i« Miyake, Bot. Mag. Tokyo Ag. 1908. 1" Williams, T. A., S. D. B. 33: 38. i« Stager, R., Bot. Zeit. Ill, 1903. i« Stevens, F. L., & Hall, J. G., Bot. Gaz. 50: 460, 1910. 1^0 Brefeld, 0., Untersuch. 12: 194. 292 THE FUNGI WHICH CAUSE PLANT DISEASE " Fulton, H. R., La. B. 105: 17, 1908. " Patterson, F., and Charles, V. K., B. P. L 171: 9, 1910. " Lodeman, E. G., N. Y. (Cornell) B. 81: 1894. " Farlow, W. G., Bui. Bussey Inst., 440, 1876. " Beach, S. A., N. Y. (Geneva) B. 40: 25, 1894. 59 Humphrey, J. E., Mass. R. 8: 200, 1891. " Garman, H., Ky. B. 80: 250, 1899. "5* Schweinitz, Syn. Fung. Carol. Sap. 134. « Ruhland, W., C. Bak. 12: 250, 1904. "0 Cooke, M. C, Grevillea 13: 63. " Clevenger, L T., Jour. Myc. 11: 160, 1905. «2 Hohnel, F. von, Sitz, K. Akad. Wis. Vienna Math. Nat. KL 118: 813 "' Shear, C. L., B. P. L B. 110 and Torr. Bui. 34: 305. " Wakker & Went. De Sietleen von het suikerriet op Java, 153: 1898. "5 Massee, Ann. Bot. 7: 515, 1893. «« Massee, Ann. Bot. 10: 583, 1896. "^ Hartig, Hedw. 12: 1888; AUegm. Forst. u. Jagd,— Zeit. Jan. 1884. "^Tubeuf, Bot. Cent. 41: 1890. « Hartig, Hedw. 12: 1888. '» Stewart, F. C. & Blodgett, F. H., N. Y. (Geneva) B. 167: 1899. '1 Pierce, N. B., V. P. P. B. 154: 1892. " Viala, Pourridie d. Vignes et d. Arbres fruitiers. " Prillieux, C. R. 135: 275, 1902. '" Behrens, J., C. Bak. 3: 584, 1897. " Whitson, E. P., Sandsten ct al, Wis. R. 21: 237. ^« Schrenk, H. von, B. P. L B. 36: 1903. " Hedgcock, R. Mo. Bot. Gard. 17: 59, 1906. '8 Heald, F. D. & Wolf, F. A., Mycologia 2: 205, 1910. '^ Tubeuf, C. von, Zeit. 3: 142, 1893. 8» Vuillemin, Jour, de Bot. 1: 315, 1888; 2: 255, 1890. 81 Smith, R. E., Cal. B. 191: 1907. 82 Viala & Ravaz, Prog. Agr. Et. Vit. 9: 490, 188. «3 Viala & Ravaz, B. Soc. Myc. d. Fr. 8: 63, 1892. 84 Jaczewski, A. von, Zeit. 10: 257, 1900. 85 Scribner, F. L., U. S. Dept. Agric. R. 109, 1886. 8« Rathay, E., Zeit. 306, 1891. 87 Chester, F. D., Del. B. 6: 1889. 88 Shear, C. L., Miles, G. F., Hawkins, L. A., B. P. L B. 155: 1909. «9 Price, R. H., Texas B. 23: 1892. ^ Reddick, D., N. Y. (Cornell) B. 293: 1911. BIBLIOGRAPHY OF ASCOMYCETES 293 >"' Prillicux, B., Soc. M. d. Fr. J^: 59, 1888. 1" Shear, C. L., B. P. I. B. IIO: 15, 1907. '" Prillicux & Delacroix, C. R. 130: 298, 1900. »" Shear, C. L., Bui. Torr. Bot. Club, 31^: 305, 1907. 1" Shear, C. L., Bui. B. P. I. B. 110. >»8 Bernard, Ch., Bui. Depot Agric. Ind. Neerland G: 1907. >" Seribner, U. S. Dept. Agr. R. 334, 1887. "8 Dudley, W. R., N. Y. (Cornell) B. lit: 1889. ""Pammel, L. H., la. B. 13: 70, 1891. »« Stewart, F. C. & Eustace, H. J., N. Y. (Geneva) B. 220: 356, 1902. ^oi Aderhold, Ber. d. deut. Bot. Ges. 18: 242, 1900. 202 Klebahn, H., Zeit. 18: 5, 1908. '«' Duggar, B. M., N. Y. (Cornell) B. 11^5: 1898. ^o-i Atkinson, G. F., Garden & Forest 10: 73, 1897. . 205 Grossenbacher, J. G., N. Y. (Geneva), T. B. 9: 1909. 2«« Jour. Bd. Agr. London, 17: 215. 2" Zeit. 3: 90; 4; 13, Frank, C. Bak. 5: 197, 1899. 208 Halsted, B. D., N. J. B. 107 and Bui. Myc. Fr. 7: 15, 1891. 2o» Potebnia, A., Ann. Myc. 8: 58, 1910. ^'o Hedgcock, G. G., J. Myc. 10: 2, 1904. 2" Jaczewski, Bull. Acad. Sc. Cracow 1892, 1893, 1894. 2'2 Cobb, N. A., Hawaii B. 5: 93, 1906, Sugar Planters Expt. Sta. 2" Atkinson, G. F., 0. E. S. B. 33: 308. 1896. s'" Atkinson, G. F., Bui. Torrey Bot. CI. 18: 1891. 21* Seribner, F. L., U. S. Dept. Agr. R. 355, 1887. 2'« Atkinson, G. F., Ala. B. 4/; 1893. 2'^ Atkinson, G. F., Bot. Gaz. 16: 61, 1891. 2'8 Stewart, F. C, B. 328: 389, 1910. 2i» Halsted, B. D., N. J. R. 381, 1893. 220 Rostrup, Tid. f. Skw. 17: 37, 1905. 221 Notizblatt k. Botan. Gart. u. Mus. Bcrlin-Dahlcm -^.- 297, 1907. 222 Voligno, Ann. R. Acad. Agric. Torino JS: 417, 1905. 223 Rathay, E., Zeit. J^: 190, 1894. 22Uohnson, J., Proc. Ry. Dublin Soc. N. S. 10: 153. 225 Prillicux and Delacroix, Bull. Soc. M. d. Fr. 6: 113. 228 Maublanc and Lasnicr, Bull. Soc. M. d. Fr. 20: 167, 1904. 22' Rev. in E. S. R. 13: 259. 228 Sheldon, J. L., J. Myc. 13: 138. 22%Smith, E. F., J. Myc. 7: 36, 1891. 230 Lawrence, W. H., Wash. B. 6J^: 1904. 294 THE FUNGI WHICH CAUSE PLANT DISEASE "1 Aderhold, R., Landw. Jahr. 23: 875, 1896. "2 Clinton, G. P., 111. B. 67: 1901. "3 Aderholdt, R., C. Bak. 6: 593, 1900. "4 Vuilleman, C. R. 108: 632, 1^89. "5 Cavara, Zeit. 3: 16, 1893. "6 Frank, B., Zeit. 5: 10, 1895. 2" Delacroix, G., Agr. Prat. Pays chauds, 7: 235, 1907. "8 Wagner, Zeit. 5: 101, 1895. 2'^ Oudemans, C. A., J. A. Proc. Soc. Sci. Konin. Akad. Wet. Amster- dam 3: 141. 2« Halsted, B. D., N. J. R. 13: 290, 1892. 2^' Pammel, L. H., la. B. 116: 1910. 2'2 Diedicke, C. Bak. 9: 317, 1902, and 11: 52, 1904. 2" Ravn, F. K., Zeit. 11: 1, 1901, and Zeit. 11: 13, 1901. 2"^ Noack, Zeit. J5; 193, 1905. 2« Viala and Ravaz, Rev. d. Vit. 197, 1894. 2« Bubak, Nat. Zeit. f. For. u. Land. 8: 313. 2« Stoneman, B., Bot. Gaz. 26. 2« Spaulding and von Schrenk, B. P. I. B. U: 1903. 2« Shear, C. L., Sc. 32: 808. 1910. 260 Southworth, E. A., J. Myc. 6: 164, 1891. 2" Clinton, G. P., 111. B. 69: 1902. "2 Hasselbring, H., Bot. Gaz. J^2: 135, 1906. "3 BurriU, T. J. and Blair, J. C, 111. B. 77: 1902. "4 Burrill, T. J., Sc. 16: 909, 1902, and 111. B. 118: 578, 1907. "5 Hasselbring, H., Trans. 111. Hort. Soc. 36: 350, 1902. 25« Sheldon, J. L., Sc. 22: 51, 1905. 2" Osterwalder, A., C. Bak. 11: 225, 1904. "8 Shear, C. L. and Wood, A. K., Bot. Gaz. 43: 259, 1907. "3 Patterson, F. W. and Charles, V. K., B. P. I. B. 171: 1910. 29« Atkinson, G. F., N. Y. (Cornell) B. ^9: 310, 1892. 261 Halsted, B. D., N. J. n. 11: 1890. 262 Edgerton, C. W., Bot. Gaz. 45: 404, 1908. 263 Sheldon, J. L., Sc. 21: 143, 1905. 264 Sheldon, J. L., W. Va. B. 10^: 1906. 265 Southworth, E. A., J. Myc. 6: 100, 1890. 266 Humphrey, J. E., Zeit. 1: 174, 1891. 267 Atkinson, G. F., J. Myc. 6: 172, 1890. 268 Edgerton, C. W., Mycol. 1: 115, 1909. 269 Barre, H. W., S. C. R. 22: 1909. 2™ Atkinson, G. F., 0. E. S. B. 33: 1896. BlBLI()(;i{APlIY OF ASCUMVCETES 295 "' Bui. Sc. j\Iyc. do France 18: 285, 1902. "2 Idem., SO: 167, 1904. "' Tavel, F., J. Myc. 5: 53, 1889. 2" Klebahn, II., J. Wis. Bot. 41: 515, 1905. 2^^ Klebahn, C. Bak. i5; 336, 1905. "" Frank, B., Zeit. 1: 17, 1891. 2" Miyake, Bot. Mag. Tokyo 23: 1909. =-« Edgerton, C. W., Bui. Tor. Bot. CI. 34: 593. "» Rolfs, F. M., Sc. ^6; 87, 1907. 2S0 Rant, A., Zeit. 17: 177, 1907. "' Montemartini, L., Riv. Path. Veg. 4: 165, 1910. 282 Delacroix, G., Bull. Soc. M. d. France, 20: 142, 1904. 2" IMassee, Kew Bull. June, 1892. 2S-' Humphrey, J. C, Mass. R. 10: 242, 1893. 285 Grossenbacher, J. G. and Duggar, B. M., N. Y. (Geneva) B. 18: 1911. 288 Fairchild, D. G., Bot. Gaz. 16: 262, 1891. 2" Hasselbring, H., 111. B. 70: 225, 1902. 288 Butler, E. J., Ann. Myc. 9: 36, 1911. 289 Eulefeld, Natw. Zeit. F. & Land. 8: 527, 1910. 29''Woronin, M. & Nawaschin, S., Zeit. 6: 129, 1896. 291 Muller-Thiirgau, C. Bak. 6: 653, 1900. 292 Ikeno, Flora, 92: I, 1903. 2" Quaintance, A. L., Ga. B. 50: 1900. 291 Cordley, A. B., Ore. B. 57: 1899. 295 Galloway, B. T., D. Ag. R. 349, 1888. 296 Potebnia, A., Ann. Myc. 8: 79, 1910. 297 Edgerton, C. W., Mycologia 2: 169, 1910. 298 Clinton, G. P., Ct. R. 319, 1906. 299 Spaulding, P., B. P. I. Circ. 35. 3»« Zimmerman, A., C. Bak. 8: 183, 1902. 3" Miyake, I., Bot. Mag. 21: 1, 1907. "'2 Essed, Ann. Bot. 25: 343, 1911. 303 Essed, Ann. Bot. 25: 364, 1911. ""• Essed, Ann. Bot. 25: 367, 1911. 305 Miyake, I., Bot. Mag. 23: 1909. 309 Hegy, P., B. Soc. M. d. Fr. 27: 155, 1911. 307 Ducomet, V., Ann. Ec. Nat. Agr. Rennes 2: 1. 308 Potebnia, A. Ann. Myc. 8: 48, 1910. 309 Potebnia, A., Ann. Myc. 8: 70, 1910. 3'o Halsted, B. D., N. J. R. 358, 1893. 3" Rand, F. V., Phyto. 1: 133, 1911. 296 THE FUNGI WHICH CAUSE PLANT DISEASE »i2 Duggar, B. M., N. Y. (Cornell) B. U5: 1898. 313 Scribner, F. L., U. S. D. Agr. R. 341, 1887. 31* Stewart, F. C, N. Y. (Geneva), B. 328: 387, 1910. 315 Clinton, G. P. Ct., R. 307, 1906. 316 Heald, F. D., Sc. 23: 624, 1906. 3" Richardson, A. E. V., Jour. Dept. Agr. So. Aust. U: 466. 318 U. S. Dept. Agr. R. 129, 1886. 3i» Atkinson, G. F., Ala. B. J^l: 1893. 32" Atkinson, G. F., 0. E. S. B. 33: 293, 1896. 321 Southworth, E. A., Dept. Agr. R. 407, 1890. 3« Edgerton, C. W., Bot. Gaz. 45: 367, 1908. 3" Galloway, B. T., U. S. Dept. Agr. R. 387, 1888. 32^ Shear, C. L., Phytop. 1: 116, 1911. 3" Reddick, D., N. Y. (Cornell) B. 263: 13, 1909, and Reddick, D., Phytop. 1: 106, 1911. 32" Griffon, E. and Maublanc, A., C. R. Sc. (Paris) 151: 1149, 1910. 3" Sadebeck, Unt. ii die Pilsegall, 1884. 3M Metcalf, H., B. P. I. B. 121: IV, 1908. 32» Metcalf, H., & Collins, J. F., B. P. I. B. Ul: 5, 1909. 33''Appel, see C. Bak. 11: 143. 331 Stewart, F. C, N. Y. (Geneva) B. 328: 318, 1910. 332 Appel 0. & Wallenweber, H. W., Arb. d. Kais. Biol Anst. f. Land Forst. 8: Heft, 1, 1910. 333 Bernard, C, Bui. Dept. Agr. Indes, Neerl. 55, 1907. 33" Rolfs, F. M., Mo. Fruit B. 17: 1910. 335 N. Y. (Cornell) B. 15: 1889. 336 Atkinson, G. F., Bui. Torrey Bot. Club 21: 224, and Bot. Gaz. 16: 282, 1891. 337 Noack, F., Zeit. 9: 18, 1899. 338 McAlpine, D., Dept. Agr. Melborne 132, 1899. 339 Zimmerman, A., C. Bak. 8: 148, 1898. 3« See Arnaud, G., Ann. Myc. 8: 471, 1910. 3" Ann. Myc. 8: 472, 1910. 3« Sheldon, J. L., Sc. 23: 851, 1906. 3-3 Pammel, L. H., Proc. la. Acad. Sc. 7: 177, 1899. 3" Parker,J. B., Ohio Naturalist, 9: 509, 1909. 3"^ Griffon & Maublanc, B. S. M. d. Fr. 26: 371, 1910. 3« Shear, C. L., Sc. 31: 748, 1910. 3" Murrill, W. A., Torreya, 6: 189, 1906. 3*8 Stone, G. E. & Smith, R. E., Mass. R. 57, 1901, 3« Larsen, L. D. H., Sug. PI. Assn. B. 10. BIBLIOGRAPHY OF ASCOMYCETES 297 3M Aderhold, R., Landw. Jahr. 25: 875, 1896 and 29: 541, 1900. 3" Brooks, F. J., Ann. Bot. 24: 285, 1910. "^Prillieux, E. and Delacroix, G., Bui. Soc. M. d. France, 9: 269, 1893. ^" Bull. Soc. My. d. Fr. 14: 24, 1898. 3" Brefeld, Unt. 9. BAsiDioMYCETEs (p. ei)!^.^:!!;^:^;":^:'?'"' This class is distinguished from all others by its basidium, which typically is a sporophore bearing on its distal end short stalks, the sterigmata, usually four, on which are borne spores, basidiospores, one on the tip of each sterigma. Fig. 215. In the great ma- jority of genera the basidia are typical and are clearly recognizable as such. In many of the lower basidiomycetes the basidia deviate somewhat from the typical form. Thus in the Hemibasidii, the smut fungi, the basidia are not typical in -that they always arise from chlamydospores, not directly from the my- ceUum, Figs. 217, 231, and that they maj' produce more than the normal number of four sporidia and these often from lateral, not terminal sterigmata. The basidia in the large group of rust fungi are also atypical. The mycelium of the Basidiomycetes is septate and branched, and is always well developed. It is often found invading cells several meters from the sporogenous structures and frequently weaves together to form rhizomorphs. Peculiar cell connections known as clamp connections, or knee joints. Fig. 287, are often found. The basidia in many genera are 298 Fig. 215. — The typical basidium with sterig- mata and spores in different stages of de- velopment. After De Bary. THE FUNGI WHICH CAUSE PLANT DISEASE 299 borne on large complex sporophores composed of the mycelial threads interwoven to form a false parenchyma. The spores may germinate by tubes or by bud- ding. Typical sexuality seems en- tirely wanting, even rudimentary or vestigial sexual organs, cer- tainly recognizable, have not been found. The group is supposed in this regard, to represent the results of extreme simplification; the sex- ual organs to have long ago dis- appeared and the simple nuclear fusions that now exist to serve functionally as fertilization. Fig. 216. — Ustilago spores showing development. After Do Bary. Key to the Subclasses of Basidiomycetes Chlamydospores at maturity free in a sorus, produced intercalary, from the mycelium ; basidiosporcs borne on a promycelium and simulating conidia 1. Hemibasidii, p. 299. Chlamydospores absent or when present borne on definite stalks Basidia septate, arising from a rest- ing spore or borne directly on a hymenium 2. Protobasidii, p. 323. Basidia nonseptate, borne on a hy- menium 3. Eubasidii, p. 393. Hemibasidii The Hemibasidii contain one order. Ustilaginales 46. 47. 124. 126-129. 131. 137 Parasitic fungi, smut producers, mycehum consisting of hyaline, somewhat septate, branched, mostly intercellular filaments, practically limited to the interior of the host; at maturity often 300 THE FUNGI WHICH CAUSE PLANT DISEASE disappearing partially or wholly through gelatinization; fertile my- celium compacting into masses and giving rise to numerous chlam- ydospores formed from its contents. Conidia rarely develop on the exterior of the host. Sori prominent, usually forming dusty or agglutinated spore-masses that break out in definite places on the host or more rarely remain permanently embedded in the tissues. Spores (chlamydospores) light to dark colored, single, in pairs, or in spore-balls, the latter often composed in part of sterile cells. The Ustilaginales are all parasites on higher flowering plants. The vegetative mycelium is mostly inconspicuous and is often Fig. 217. — Ustilago. 2, pruinycelium with nucleus in mi- tosis; 5, witii 4 nuclei; 6, with conidia. After Harper. distributed very widely in the host plant without giving external evidence of its presence until time of spore formation. It sends variously formed botryose or spherical haustoria into the host cells. At time of maturity of the fungus, the mycelium develops in great abundance at certain special places in the host, often in the ovary, leading to the development of large mycelial structures in the place of the host tissue. The chlamydospores develop directly from the vegetative my- celium; new and numerous transverse cell-walls are formed; the resulting short cells swell, round off and become coated with a gelatinous envelope. This later disappears and the spores develop a new, thick, usually dark, double wall which is variously marked. THE FUNGI WHICH CAUSE PLANT DISEASE 301 The chlamydo.spores may be simple or compound, fertile or in part sterile and are variously shaped and marked as described in the genera below. The chlamydospores may germinate at once or after a more or less protracted rest interval. In germination in water or nutrient solution (manure water, etc.) a short tube is protruded, the pro- mycelium, this differing in character in the two famiHes, Figs. 217, 231. From the promycelium of most species there develop conidia, (often called sporidia) 1-12 or even more. The promycelium is regarded as homologous wnth the basidium of the other basidio- mycetes and the conidia as basidiospores. The conidia in suitable nutrient solutions often undergo repeated and indefinite budding closely simulating yeast cells in appearance. Fusion of conidia is not uncommon. Fig. 218. Conidia finding lodgment pa^^^ in suitable plant parts under suitable ^JS^T^ environmental conditions give rise to infection. The points at which in- fection can occur are very diverse with different species and will be considered under the separate species below. *^ r-,, , ,. „ 1- 1 . Fig. 218. — Ustilago. 17, ponidia The vegetative cells are binucieate fusing; 19, promyceiiai cells in TiUetia, multinucleate in the Usti- ^^^^^ ^'f'Verii^S^el! '"■ laginacea}.^'^^^ The young chlamydo- spores were shown by Dangeard ^•^^■' in the case of Doassansia, Entyloma, Ustilago and Urocystis to be binucieate. These two nuclei, according to Dangeard, later fuse rendering the mature spore uninucleate. In germination the one nucleus passes into the promycelium, then divides mitotically Fig. 217, 2. A second division gives four nuclei (Fig. 217, 5) the spore nuclei.'* In the fusions of smut conidia Federly has found an accom- panying nuclear fusion, in salsify smut, while Lutman finds similar fusion in the conjugating promyceiiai cells of oat smut.^ Whether or not these nuclear fusions represent a sexual act is a much controverted point. There are according to Clinton about four hundred species in America.^' ^"'^ 302 THE FUNGI WHICH CAUSE PLANT DISEASE Key to Families of Ustilaginales Promycelium usually with sporidia lateral at septa 1. Ustilaginaceae, p. 302. Promycelium with clustered terminal sporidia 2. Tilletiaceae, p. 314. Ustilaginaceae Sori usually forming exposed dusty or agglutinated spore- masses. Germination of chlamydospores by means of septate promycelia which give rise to terminal and lateral sporidia or else to infection-threads. Key to Genera of Ustilaginaceae Spores single Sori dusty at maturity Without definite false membrane 1. Ustilago, p. 303. With false membrane of definite fungous cells 2. Sphacelotheca, p. 310. Sori agglutinated at maturity Firmly agglutinated into conspicuous tubercular nodules 3. Melanopsichium. Developed around a central columella (rarely dusty) 4. Cintractia. Spores chiefly in pairs Sori agglutinated (on leaves) 5. Schizonella. Sori dusty (inside peduncles) 6. Mykosyrinx. Spores in balls of more than two Sori dusty or granular Spore-balls often evanescent; spores olive-brown or black-brown 7. Sorosporium, p. 312. Spore-balls rather permanent; spores yellowish or reddish, with markings only on free surface 8. Thecaphora, p. 313. Spore-balls quite permanent; spores ad- hering by folds or thickenings of outer coat 9. Tolyposporium, p. 313 THE FUNGI WHICH CAUSE PLANT DISEASE 303 Sori asslutinated Spore-balls (variable) composed of thick-walled spores 10. Tolyposporella. Spore-balls with peripheral spores and central sterile cells 11. Testicularia. Of these genera numbers three to eleven inclusive occur on un- important plants. Among them are: Polygonum, Rynchospora, Psilocary, Cyperus, Carex, Luzula, Juncus, Fimbrystylis, Cissis; various unimportant grasses, members of the Carduacese, Faba- cese, Nyctaginacese, Amarantaceae, Cyperacese, Dracenacese, and Eriocaulacese. The most important genera are Ustilago and Sphacelotheca. Ustilago (Persoon) Roussel (p. 302) Sori on various parts of the hosts, at maturity forming dusty spore masses, usually dark colored; spores single, produced irregu- larly in the fertile mycelial threads which early entirely disappear through gelatinization, small to medium in size; germination by means of a septate promycelium producing only infection-threads or with sporidia formed terminally and laterally near the septa; sporidia in water usually germinate into infection-threads but in nutrient solutions multiply indefinitely, yeast- 4 fashion. About two hundred species, seventy-two of which are given by Clinton ^ as occurring in America. Besides the species discussed below many others occurring upon grasses or other plants of minor value are omitted. U. avenae (Pers.) Jens.^^. ne, ii7. 124, 125 Sori in spikelets, rarely in leaves, forming a dusty olive-brown spore-mass, about 6-12 mm. Fia. 219.— U. aye- long by half as wide, usually rather completely in water. After destroying floral parts, eventually becoming dissi- *'^*°'^' pated; spores lighter colored on one side, subspherical to spherical though often elongate, minutely echinulate, 5-9 ju in length, widespread on oats. The fungus was known by the name Ustilago as early as 1552 304 THE rUNGI WHICH CAUSE PLANT DISEASE and was called U. avenae in 1591. The species of Ustilago on oats, wheat and barley were considered identical until Jensen ^ showed that they are not intercommunicable. Wolff ^ showed that seedlings can be infected through the first sheath leaf. Brefeld ^ studying infection more closely found it to be accomplished by germ tubes from sporidia and that plants are free from infection after the growing leaves have pushed one centimeter through the sheath leaf. The mycelium, after infec- tion, grows through the plant until blooming time when it seeks the ovaries and the enclosing glumes in which it forms a mycelial mass, which soon changes into spores. In nutrient solutions the conidia bud indefinitely, while on the host plant they produce infecting hyphae. Germination was first studied by Prevost.^ It occurs read- ily in water, a well de- veloped promycelium resulting in about twenty-four hours. Fig. 219. The sporidia are mostly narrowly elliptical. Fusion of sporidia is common. The promycelia are usually four-celled and occasionally branch, especially near the base. [i'«' ''' U. crameri Korn.-^- Sori in the spikelets, infecting all of the spike, ovate, about 2-4 mm. in length, chiefly destroying in- FiG. 220. — Growing point of the stem of barley. rl K 1 t • Much enlarged, showing smut mycelium. After ^^^ ana Dasai parts, ^^'^^®- spores reddish-brown, chiefly ovoid to subspherical though occasionally more elongate and irregular, smooth, with usually pitted contents, chiefly 8-11 n in length. THE FUNGI WHICH CAUSE PLANT DISEASE 305 The promycelium is much branched but no sporidia are pro- duced. The smut commonly affects the ovaries of Panicum and Setaria. In America it has been collected on millet in several states. U. crus-gaUi T. & E.i"^ Sori often encircling stems at nodes or at the juncture of the inflorescence, infecting both stem and leaves, prominent, often nodular, one to several centimeters in length, protected by a tough hispid membrane which upon rupture discloses an olive-brown dusty spore-mass; spores ovoid to spherical, occasionally more elongate, rather bluntly echinulate or even verruculose, chiefly 10-14 /x in length. On Panicum crus-galli throughout the United States. U. bulgarica Bub. is on Sorghum vulgare. European. U. medians Bieden, on barley, is closely like U. hordei.^'* U. scorzonerae (A. & S.) Schr. on Scorzonera is very close to U. tragopogonis-pratensis. U. sacchari Rab.^"^ Spore-mass black, spores globose or angularly globose, 8-18 /x in diameter, olive-brown or rufous, epispore thick, smooth. On sugar-cane throughout the tropics, especially in the old world. In Java this fungus has been reported as the cause of serious damage. Barrett observed it in Trinidad, where the damage was less extensive. The leaves especially the young ones which have not yet sepa- rated from each other are the parts affected. From the upper part of the affected cane, as a rule, no secondary shoots arise, and those which do arise from the lower part become infected in their turn. The discolored whip-like structure at the end of an attacked cane becomes dusty and black and contains the spores of the fungus. U. hordei (Pers.) K. & S.-^- ''^' '^' Sori in spikelets, forming an adhering purple-black spore-mass, about 6-10 mm. in length, covered rather permanently by the trans- parent basal parts of the glumes; spores lighter colored on one side, usually subspherical or spherical, smooth, 5-9 ju, the most elongate rarely 9-11 /x in length. Common on barley. This was first recognized as distinct from the oat smut in 1591 306 THE FUNGI WHICH CAUSE PLANT DISEASE by Lobelius.^° Persoon in 1801 first gave a definitely recognizable description.^^ In 1888 the species was separated from the other smut on barley.^^ The spores germinate freely in water by one, rarely two, tubes, usually 4-celled, and produce abundant sporidia; these increase by budding, produce germ tubes, or fuse with each other. U. levis (K. & S.) Mag.24- "^ Sori in spikelets, forming a black-brown adhering spore-mass, sometimes small and entirely concealed by the ^ N glumes but usually evident and destroying inner ^ U and basal parts; spores lighter colored on one side, subspherical to spherical or rarely elongate, smooth, 5-9 fx, the most elongate rarely 11 m in length. On oats throughout America and Europe, prob- ably more common than records show as it is very difficult to distinguish from U. avense from which it differs chiefly in its smooth granular spores. XJ. macrospora Desm. Sori in leaves and glumes, generally showing as linear striae, but often more or less merged, at first covered by the epidermis, but this later rup- turing and disclosing black-brown dusty lines of spores; spores medium to dark reddish-brown, chiefly ovoid to spherical or occasionally some- what irregular and elongate, coarsely verrucose, at circumference usually showing the projections as tinted blunt scale-like appendages, sometimes even semi-reticulate, 12-19 M in length. On various species of Agropyron in Europe and America. U. nuda (Jens.) K. & S.^^. ne Sori in spikelets, forming a dusty olive-brown spore-mass, about 6-10 mm. long by half as wide, temporarily protected by a thin membrane which soon becomes dissipated leaving the naked rachis behind; spores lighter colored on one side, minutely echinulate, subspherical to spherical or occasionally elongate, 5-9 /j, in length. In Europe and America. This smut on barley is distinguishable from the covered smut, U. hordei, by its olive-green spore-mass and by its early shedding of spores. As a rule, each spikelet, ex- FiG. 221.— U. le- vis, germina- tion in modi- fied C o h n ' 8 solution. Af- ter Clinton. THE FUNGI WHICH CAUSE PLANT DISEASE 307 cept the awn and rachis is entirely transformed into smut. In water and in nutrient solutions the spores germinate by a single promycelium, 1 to 3-septate, and often branched, but without sporidia. That infection is floral in loose smut of both wheat and barley was first shown by Maddox ^^ and the fact was corrob- orated by Wakagawa,^^ Brefeld ^'^ and Hecke.^*"' ^'^ The my- celium has been demonstrated in the embryo by Broili.^^^ The spores falling between the glumes germinate, penetrate the ovary wall, and into the growing point of the embryo. The mycelium here lies dormant until the seed germinates, when it grows, keeping pace with the growing point throughout the season and finally invading the ovaries to produce its spores. The infection of the pistil, the penetration of the integuments and the nucellus and embryo sac was followed in microtome sec- tions by Lang.^^^ The embryo was reached by the mycelium some four weeks after infection of the pistil. In resting grains the my- celium is abundant in the scutellum as well as in all embryo parts except the roots. Cross inoculation by Freeman and Johnson ^^ from barley to wheat and the reverse gave negative results. The optimum time for infec- tion has been determined as the period of full bloom. U. perennans Rost.^^^' "^ Sori in spikelets, more or less destroying the basal and inner parts, sometimes even running 'germination 'm down on pedicels, oblong, about 3-8 mm. in ^°utio*i? After length, with dusty, olive-brown spore masses; Kellerman and mycelium perennial in perennial parts of host; ^ se. spores chiefly subspherical or spherical, occasionally ovate to el- lipsoidal, usually lighter colored on one side, more or less minutely echinulate, especially on the lighter side, 5-8 n in length. On the tall oat grass throughout its range. U. rabenhorstiana Kiihn occurs on several species of Panicum. U. tritici (Pers.) Rost.^^- ^i". 12-1, 125. 128 Sori in spikelets, forming a dusty olive-browm spore-mass, about 8-12 mm. long by half as wide, usually entirely destroying floral 308 THE FUNGI WHICH CAUSE PLANT DISEASE parts and eventually becoming dissipated and leaving behind only the naked rachis; spores lighter colored on one side, usually sub- spherical to spherical, occasionally elongate, minutely echinulate especially on the lighter side, 5-9 ix in length. On wheat where- ever cultivated. The smut mass is covered at first by a very delicate membrane. Infection is floral as described for U. nuda. The spores germinate in water by a long 2 to 3, or even 6 to 7-septate, promycelium, often curved. In nutrient solutions the ;i4. — 25. ^^- Fig. 223. — U. zeae, stages in spore development. After Knowles. promycelium branches profusely but sporidia are few or are en- tirely absent. U. zese (Beck.) Ung.i^- ""'• '''-'-'• '^^' ''''' '''- Sori on any part of the corn plant usually prominent, forming irregular sweUings from a few millimeters to over a decimeter in diameter, at first protected by a sort of false white membrane composed of plant cells and semi-gelatinized fungous threads, soon rupturing and disclosing a reddish-brown spore-mass; spores ellipsoidal to spherical or rarely more irregular, prominently though rather bluntly echinulate, 8-11 fi the most elongate 15 /i in length. The germina.tion of the spores, which occurs but poorly in water, was first studied by Kiihn ^^ in 1857. In 1874 Kiihn saw the pene- tration of the germ tubes through the epidermis of the corn plant. Brefeld showed that the spores germinate well in nutrient solu- tions and that secondary spores are formed ; also that corn can be infected by the sporidia at any point on its surface above ground THE FUNGI WHICH CAUSE PLANT DISEASE 30d when the tissues are soft and actively growing; and that infection is local on the host.^^ It is now known that the chlamydospores are capable of ger- mination without hibernation and that they remain viable one, two, perhaps more years. It was shown by Brefeld in 1895 that the chlamydo- spores produce conidia in the air freely. It is these, air-borne, arising from spores on the ground, ma- nure, etc., which are chiefly responsible for infection. They must reach the plant on a susceptible part and under suitable con- ditions of moisture. The germ tubes from the conidia penetrate the epidermis, grow through or between the cells, Fig. 223, with an irregular my- celium which branches Fig. 224. — U. zese. 1, germination after three days in water; 2, similar but in air showing air sporidia. After Clinton. profusely and calls forth great hypertrophy of the surrounding host tissue. In sporing, the mycelium forms a great number of short, slender, irregular branches which make up a close tangled network in the diseased tissue. These slender branches swell, gelatinize, and portions of them round off as spores. Fig. 223. U. striaeformls (West.) Niess.-^' ^-'^ Sori in leaves, sheaths and rarely in the inflorescence, from short to linear, often extending, apparently by terminal fusion, for several centimeters, also occasionally fusing laterally to cover most of the leaf; at first covered by the epidermis but this is soon rup- tured and dusty brown to black, linear masses of spores become 310 THE FUNGI WHICH CAUSE PLANT DISEASE scattered and the leaves become shredded; spores usually ellip- soidal to spherical, occasionally irregular, prominently echinulate, chiefly 9-14 /x in length. It appears to be perennial. The spores germinate sparsely. The promycelium is long, branched, septate, and produces no conidia. On numerous species of grass, including red top, timothy and species of Poa and Festuca throughout Europe and America. Species of less importance, not all found in America are: U. schiriana Hem. which attacks bamboo ; ^^ U. secalis Rab. is European on rye; possibly a Tilletia. U. esculenta P. Hen. which causes swellings on Zizania which are eaten in the orient; U. vaillantii Tul. in the sexual organs of the Liliacese; U. panici-miliacei (Pers.) Wint. on Panicum miliaceum; U. tragopogi-pratensis (Pers.) Wint. on the flowers of Trago- pogon; U. cruenta Kiihn, widespread in Europe on sorghum; U. violacea (Pers.) Fcl. on the anthers of various members of the Caryophyllaceae; U. tulipae Wint. on tulips and related hosts; U. vrieseana Vuill. on eucalyptus roots, a very doubtful species; U. sphaerogena Burr, on Panicum crus-galli. The fungus described as U. fischeri Pers. from Italy on corn is a Sterigmatocystis as is also U. phcenicis Corda on date fruits and U. ficuum Reich on figs. Sphacelotheca De Bary (p. 302) Sori usually in the inflorescence, often limited to the ovaries, provided with a definite, more or less temporary, false membrane, covering a dusty spore-mass; and a central columella, usually formed chiefly of the host plant's tissues. The false membrane is composed largely or entirely of sterile fungous cells which are hyaline or slig