alias ^oofe ^o.SSOTS ^orti} eastern ^nt&ersity l^tbrHry F LIBRARY RULES This book may^'te kept..OXXC^ weeks. A fine of tjyo cents will be charged for each day books or magazines are kepV overtime. Two books may be borrowed from the Library at one time. Any book injured or lost shall be paid for by the person to whom it is charged. No member shall transfer his right to use the Library to any other person. PLANT DISEASE FUNGI THE MACMILLAN COMPANY NEW YORK • BOSTON • CHICAGO • DALLAS ATLANTA • SAN FRANCISCO MACMILLAN & CO.. Limited LONDON • BOMBAY • CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Ltd. TORONTO / PLANT DISEASE FUNGI F. L. STEVENS, Ph. D. PROFESSOR OF PLANT PATHOLOGY IN THE UNIVERSITY OF ILLINOIS THE MACMILLAN COMPANY 1925 All rights reserved ^^ii-- Copyright, 1913 and 1925, By the MACMILLAN COMPANY Set up and electrotyped. Published June, 1925. FRlNTEi:) IN THE UNITED STATES OF AMERICA BY THE BERWICK & ^MITH CO. PREFACE The aim of this book is to present the more important facts concerning the morphology and taxonomy of the fungous para- sites that affect plants of importance in the continental United States, with some discussion, also, of the more significant facts of morbid histology. 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. In order to avoid duplication of the subject matter of "Diseases of Economic Plants" gross descriptions of diseased hosts are omitted from this volume. Bibliographic citations given either in "Diseases of Economic Plants" or in "The Fungi which cause Plant Disease," in general, are not repeated here and the student is referred to these two texts for additional references to literature. The citations herein given refer to articles either more recent than those of the previous work or are advisable owing to a different viewpoint in the pres- ent book. Effort has been made to present at least one illustra- tion of each genus of importance. The keys, for the most part, are abbreviated or otherwise modified from those given in "The Fungi which cause Plant Disease." All keys are abridged by the omission of genera or larger groups whose representatives are of minor importance. The author wishes to express thanks for suggestions and criticism of the manuscript to F. W. Tanner who read the por- tion on Bacteria; G. P. Clinton, Ustilaginales; E. C. Stakman, and H. R. Rosen, Uredinales; C. L. Shear, the anthracnose fungi; E. A. Burt, certain Basidiomycetes ; CD. Sherbakoff, the genera Fusa- rium and Nectria; and to B. B. Higgins for kindly reading criti- cally the entire book in proof. F. L. Stevens. Urbana, Illinois. March, 1925. {^S07S CONTENTS PAGE Introduction 1 Division I, Myxomycetes 3 Division II, Schizomycetes 9 Division III, Eumycetes 50 Class Phycomycetes 56 Class Ascomycetes 87 Class Basidiomycetes 210 Fungi Imperfecti 331 Index 441 PLANT DISEASE FUNGI PLANT DISEASE FUNGI INTRODUCTION A large percentage of all plant diseases is caused by fungi. Fungi are devoid of chlorophyll and while transpiration, respira- tion, and true assimilation are the same as with the green plants, photosynthesis or starch manufacture cannot be accomplished by them. Sunlight being thus unnecessary 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 that prey upon living things are called parasites. Those living upon dead things are saprophytes. 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 when ripe, a resting seed, the cells of the potato tuber in winter, are undoubtedly alive, yet their activity is so slight that many organisms can gain a foothold upon these stages of the plant that cannot do so at more vigorous periods of its existence. 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 1 2 PLANT DISEASE FUNGI bear important relation 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. Study of the fungi present in diseased tissues and of their relation to these tissues is of great importance as an aid in diagnosis. If no fungi are found in sufficient abundance to account for disease, after careful search in all parts of the plant, it may ten- tatively be assumed (flowering plants and animal parasites being similarly excluded) that the disease is non-parasitic in origin. If fungi are found their morphology must be ascertained and their taxonomic position determined in order to render diagnosis certain and to make available the hterature pertaining to the disease. It is the purpose of the following pages by keys and de- scriptions to aid the student in such studies. 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. Key to the three Divisions important as plant parasites: Vegetative body a multinucleate, naked Plasmodium Division I. Myxomycetes, p. 3. Vegetative body a single, walled cell, reproduction by fission (by conidia in a few forms) Division II. Schizomycetes, p. 9. Not as above: vegetative body usually filamentous, reproduction by various means Division III. Eumycetes, p. 50. DIVISION I MYCETOZOA, MYXOMYCETES, PLASMODIO- PHORACE^ 1 2 (p 2) The distinctive character of the members of this division is that the vegetative plant body as it approaches maturity consists of a mass of naked protoplasm, the Plasmodium, formed by the coales- cence of numerous swarm cells, each unwalled. The Plasmodium eventually gives rise to walled spores; they in turn germinate, pro- ducing amoeboid swarm cells, which soon become flagellated. These swarm cells multiply by division and ultimately revert to the amoe- boid condition and coalesce, bringing about a return to the plas- modial stage. The fungi herein considered may be separated, on the purely artificial character of parasitism, into two groups. Parasitic Plasmodiophoraceae, p. 3. Saprophytic Mycetozoa, p. 7. Plasmodiophoraceae 3 Intracellular parasites, vegetative stage plasmodial; spores formed by the simultaneous breaking up of the Plasmodium into an indefinite number of independent cells. Since the protoplasm of the parasite rests within the proto- plasm of the host this constitutes parasitism of the strictest type. Key to Genera of Plasmodiophoraceae Spores free, spherical 1. Plasmodiophora, p. 4. Spores united into groups Spores in groups of more than four Spores forming a spongy spore-ball 2. Spongospora, p. 5. Spores in a cyst 3. Cystospora, p. 6. ^ Lister, A. A monograph of the mycetozoa. British Museum of Natural History, London, 1911. 2 Osborn, T. G. B. The life cycle and affinities of the Plasmodiophoraceae. Rept. Brit. Ass. Adv. Sc. Portsmouth, 572, 1911. ^ Schwartz, E. J. The Plasmodiophoraceae and their relationship to the Myce- tozoa and the Chytridese. Ann. Bot. 28: 227, 1914. 3 4 PLANT DISEASE FUNGI Plasmodiophora Woronin (p. 3) This genus is parasitic in the living parenchyma of the roots of plants, Plasmodia filling the cells and causing galls at the point of attack. Only one species is of importance. P. brassicae Wor. is parasitic on crucifers generally and per- haps on members of other families; the Umbelliferae and cucurbits. The parasitized cells especially, and the adjacent cells as well, are stimulated to enormous overgrowth; (hypertrophy) and there is also large increase in the number of cells by abnormal cell divi- FiG. 1. — Cross-section of a root badly infected with P. brassicae. After Woronin. sion (hyperplasia) resulting in the formation of galls, often very large, on the underground parts of the host. In early stages of the disease of a cell, nuclear and cell division is not seriously affected, but in later stages both processes cease and the host nucleus degenerates. 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, the xylem is reduced and phloem increased PLANT DISEASE FUNGI projportionately. The amount of stored starch is much less than in normal tissues. f Fig. 2. — Germination of the spores and development of the myxamebae. After Woronin. Infection occurs through the root hairs by the single amoeboid cells, and groups of diseased cells arise from repeated division of a cell after its infection. Passage of the organism from cell to cell also occurs. In the enlarged host cells the protoplasm appears abnormally dense and fine grained. Eventually the lumen of the cell is largely occupied by the crowded, amoeboid individuals, which later fuse into Plasmodia, the nuclei of which en- large and undergo simultaneous mitotic division. Still later the mass divides into uninuclear segments each of which matures to a spore 1.9-6.9 /j. in diameter, covered by a thin, smooth, colorless mem- brane. Spore germination may best be studied in a muck-soil filtrate, where in from five to twenty-four hours uninucleate zoospores are produced. The zoospores are differentiated into an inner granular, and an outer hyaline region, the hyalo- plasm, which may extend to form pseudo- Fiq. 3 —p. brassicae: host cell full ,. ' , • • ji 11 1-1 of spores. After Lotsy. podia, thus givmg the cell an amoeboid movement in addition to that due to the single long cilium. Seedlings raised in soil inoculated with chopped roots bearing the disease become badly diseased as do also seedlings upon which infected water is poured. Other species have been reported on hops, tomato, orchid. Spongospora Brunchorst ^ (p. 3) S. subterranea (Wallr.) Johnson causes the powdery scab of potato tubers, also galls on the roots, stolons and stems, and galls on tomato roots. 1 Osborne, T. G. B. Spongospora subterranea (Wallroth). Johnson. Ann. Bot. 25: 271, 1911. 6 PLANT DISEASE FUNGI Infection of growing potato tubers by S. subterranea is accom- plished not by separate amoebse, as has previously been supposed, but through the action of a Plasmodium which invades the tissue and infects a large number of cells at each point of contact. The diseased host cells are consumed by the parasite resulting in pits or cavities. At the same time adjacent host cells are stimu- lated to increased growth and division. The parasite is handed down to new cells as division of parasitized cells occurs. The Plasmodia at maturity produce spores which adhere in loosely aggregated, spongy, ovoid to spherical, balls which are about 50 /JL in diameter. The individual spores are about 4 /i in diameter. Cystospora Elliott (p. 3) This genus differs essentially from Plasmodiophora in that the plasmo- >.^. wMW 31 -^ tj .fj^^'^X :?.>. ~i-<»-a Fio. 4. — S. subterranea. C, The amoe- bae are coalescing to form the Plas- modium. E, Mature spore balls in an enlarged host cell. After Os- borne. Fig. 5. — C. batatae. Cells of a growing-point occupied by sev- eral individuals in the amoe- boid stage, a, parasites; b, host cell nuclei; c, Plasmodium invad- ing cell. After Elliott. dium within the host cell becomes encysted before formation of the spores, Fig. 6. Each cyst bears several hundred spores. C. batatae (Ell. & Hals.) Elliott This organism was originally described by Halsted under the PLANT DISEASE FUNGI 7 name Acrocystis as the cause of soil rot of sweet potatoes, and was later by Elliott referred to the Plasmodiophoraceae. Elliott's description is essentially as follows: Fig. 6. — C. batatae. Row of host cells occupied by cysts of the Plasmodium. a, host cells containing two cysts. After Elliott. In large, shallow pits a Plasmodium is present, the host cells invaded, and the contents dissolved. In the root tips swarm spores invade the host cells, pass to the amoeboid stage, multiply rapidly, then form a Plasmodium which encysts. Inside of the cyst hun- dreds of swarm spores develop and later emerge to penetrate other cells. ■^' ^1 1 '"^X Fig. 7. — Physarum cinereum. After Lister. Mycetozoa (p. 3) This group comprises some forty-nine genera and about two hundred and fifty species of great variety and beauty. The Plas- modium, which varies from a millimeter or less to several deci- 8 PLANT DISEASE FUNGI meters in diameter, produces either flat, encrusted masses of spores, aethalia, or develops spores in sporangia which show some superficial resemblance to very small puff balls. Fig. 7, The inte- rior of the sporangium is often permeated by a threadlike structure, the capillitium. They are not parasites but occasionally injure plants by overgrowing them. The species most often found so doing is Physarum cinereum Pers. which forms its tiny, sessile, gray sporangia in great numbers on living plants, often smothering them. The peridium is lime- charged, as are also the nodes of the capillithim. The spores are brown or violet, and warty. Physarum gyrosum Rost. and Musi- lago spongiosa Morgan are credited with similar injury. DIVISION II BACTERIA, SCHIZOMYCETES ^ ^ (p. 2) Bacteria are extremely minufce, unicellular organisms, which in outline present three primary forms each of great simplicity, namely the spheres (cocci), the straight rods (bacteria), the curved rods (spirilla). In addition to these forms which comprise the vast majority of known species of bacteria there are also bacteria consisting of fila- mentous bodies, either simple or branched, attached or free. In both structure and physiology bacteria are allied to the vegetable kingdom and in it most closely to the blue green algae. Bacteria are inconceiv- ably small. Most of the ^^^ spherical bacteria fall within ^ q the limits of from 0.5 to 1.5 II in diameter. Among the rod and curved bacteria the length in most species is be- tween 1 and 1.5 ^u, the di- ameter between 0.5 and 1 U. ^'^- ^•-'^^^ ^"^^T *^P' ^'°'' f. bacteria,- a. spheres; fa, rods; c, spirals. After Conn. Among the largest species is B. megatherium, 2.5 x 10 /^; Clostridium butyricum, 3 x 10 \i', and Spirillum volutans, 13 to .50 \x long. Among the smallest are Spirillum parvum 0.1-0.3 /z in diameter and Pseudomonas indigo- fera 0.06 x 0.18 m- 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 11 thick. It would therefore take . about 200 bacteria of ordinary size or 400 mod- FiG. 9.— This dot is erately small or 20 very large ones placed end 1 mm. in diameter. ^^ ^^^ ^^ ^^^^j -^ j^^^^j^ ^^^ thicknCSS of this paper. It would take 1571 ordinary bacteria (1 x 2 /i) end to end to reach around the circumference of a dot 1 mm. in diameter 1 Smith, E. F. Bacterial diseases of plants. W. B. Saunders Co., Philadelphia, 1920. ^ Bacteria in relation to plant disease. Vols. 1-2-3, Carnegie Institution, Wash- ington, 1905. 9 10 PLANT DISEASE FUNGI (Fig. 9), 500 to equal its diameter, 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 millimeter, making no allow- ance 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 in the eubacteria is by fission or direct division of one cell, the mother cell, into two, the daughter cells. Fig. 10. The rapidity with which fission can proceed de- pends, of course, upon conditions of environment, ranging from no growth at all, due to cold, lack of nutriment, presence of inhibit- Fig. 10. — Diagram illustrating the fission of bacteria, bacilli and cocci. After Novy. ing substance, to a maximum that varies with the species. For bacteria in general in very favorable environment, with proper temperature 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 divi- sions each 30 minutes it will be (16, 777,2 16) 2. If cell division be in one direction only and the resulting daugh- ter cells remain undisturbed, a thread-like row results. If cell di- vision 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 bacterial cell. 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 organs of locomotion. 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, or scattered over the whole surface, diffuse or peritrichiate. Within the wall is the protoplast consist- ing of a peripheral layer, inner strands, imbedded granules and vacuoles bearing cell sap. The existence of a nucleus comparable to that in higher plants is a much controverted point. PLANT DISEASE FUNGI 11 mm Spores : Typically a bacterial spore consists of a highly refrac- tive, ovoid, walled body within the mother cell. They are most fre- quently met among the rod forms, and are rare among the spirilla and cocci. None are known among the important plant pathogens. This body possesses high resistance to ordinary stains, a great tenacity against decolorizing if it be once stained, a higher resistance against adverse temperatures and adverse conditions generally than do vegetative cells, and finally the ability to germinate and thus aid in perpetuating the species. While the abso- lute number of bacterial species that form spores is large, comparatively thej^ are few. In the simplest cases of spore formation, the protoplasm becomes more dense in some part of the mother cell, the remain- Fiq. ll.— spores of bacteria showing their position within ing protoplasm of the '^' '^"- After Frost & Mc-Campbell. cell is drawn around the denser mass, and the whole resulting dense region l^ecomes enclosed within a special wall. Usuall}^ in this process nearly all the protoplasm of the mother cell, the sporangium, is used. The mother cells during spore formation may remain of the normal vegetative size and shape; they may take on (B. sub tills) or abandon (B. megathe- rium) the habit of thread formation. Bacteria of many species become swollen at the point where the spore develops, Figs. 11 and 13; be this in one end (Vibrio rugula) or in the middle (B. in- flatus) . The swelling at the end is very common, giving rise to the peculiar and characteristic form known as ''nail head'' or "drum stick" bacteria. In nearly all species of the Eubacteria the spores are solitary. There are three modes of spore germination. The most common, polar germination, consists in a rupture of one pole of the spore and the development of a normal vegetative cell through the open- ing. The second mode, equatorial. Fig. 13, consists in a rupture in the side instead of the end of the spore. The third mode, absorp- FlG 12. — Spore formation in bac- teria. After Fischer. 12 PLANT DISEASE FUNGI tion, consists in a direct development of the whole spore into a vegetative cell. In suitable environment germination may occur immediately after formation; if conditions be unsuitable it may be delayed for many years. Fio. 13. — Spores of bacteria, showing bispored cells, spore formation and spore germination. After Prazmowski, de Bary and Koch. Under certain conditions most bacteria undergo abnormal changes in form, becoming elongated, branched, swollen, bulged, curved, or variously, usually irregularly, distorted. Such are termed involution forms. They are, in most cases, due to un- favorable conditions of temperature and nutriment, and the bacteria resume their normal form when again in normal en- vironment. The branched forms found in root tubercles, after the period of luxuriant growth has passed, and the branched thread-like growth of the bacterium of human tuberculosis upon artificial media, are by many regarded as involution forms. Bacteria were discovered by Loewenhoek in 1683. That they do not originate spontaneously was shown by Pasteur in 1860^. The first disease producing bacteria were recognized in anthrax by Pollander & Davaine in 1849; and the first definite proof that bacteria actually cause animal disease was made by Koch with anthrax in 1875-1878. The first plant disease definitely to be ascribed to bacteria was the pear blight by Burrill in 1879. The PLANT DISEASE FUNGI 13 invention of the cotton plug, Schroeder & Dusch, 1853, the gelatine method of plating for the isolation of species, Koch, 1881, and the use of stains, Weigert, 187t5, were practically necessary prerequi- sites to any considerable advance in bacteriology. For long it was contended, especially by European bacteriologists, that bacteria do not cause plant diseases but most convincing proof to the contrary was adduced by E. F. Smith. Entrance to the host plant is made in various ways, very often through wounds, particularly wounds caused by insects, through roots, stomata, water pores, through delicate tissues as blossoms, etc. Once in the tissue, bacteria may migrate rapidly by means of the vessels, intercellular spaces or more slowly through cavities dissolved by the aid of enzymes. Bacteria are disseminated by wind and water, which may carry them to great distances, also by tools, hoofs of animals, shoes of man and similar means; they ]are in some instances conveyed from plant to plant by insects., e. g. Bacillus trachei- philis on Cucurbits. Though bacteria parasitic on plants are not spore-bearing they may persist in virulent form in soil for long periods. Classification. Several systems of classification and nomen- clature are now in use in America. The system of Migula, pro- posed in 1894, was for years extensively employed by plant path- ologists. In 1905 E. F. Smith made suggestions, since then to some extent followed, regarding the names to be used for certain genera. In 1920 the nomenclature committee of the Society of American Bacteriologists made radical changes both in system and nomenclature. The System of Migula, in so far as it applies to important plant pathogens, and adding the Actinomycetales, is given below. Fol- lowing this are given the names that would be employed for these genera if the other systems referred to were used. The system of Migula will be used throughout this book. SCHIZOMYCETES (p. 2) Fission plants, without phycochrome, dividing in one, two or three directions of space. Reproduction by vegetative multiplica- tion. Resting stages, endospores, exist in many species; motility by means of flagella in many genera. 14 PLANT DISEASE FUNGI Key to Orders, Families, and Genera of Schizomycetes Cells without sulphur or bacterio-purpu- rein, not filamentous, not branched .... Eubacteriales. Cells in free condition gobular; in di- vision somewhat elliptical Coccaceae. Nonflagellate; division in two direc- tions 1. Micrococcus, p. 18. Cells long or short, cylindrical, straight, division in one direction Bacteriaceae. Nonflagellate 2. Bacterium, p. 18. Flagellate Flagella diffuse 3. Bacillus, p. 40. Flagella polar . 4. Pseudomonas, p. 21 Cells filamentous, often branched Actinomycetales Conidia present Actinomycetaceae Mycelium much branched and breaking into segments that function as conidia 5. Actinomyces, p. 48. The species of the two other families of these orders, and of the two other orders of the Migula system, some 25 genera in all, are, so far as is known, unimportant in their relation to plant disease. All of the known bacterial plant pathogens belong to one or other of the first two families of the Eubacteriales or to the genus Actino- myces. The specific characters of bacteria are chiefly chemical or phys- iological and rest in the relation of the forms to oxygen, gelatine liquefaction, fermentation of various sugars, acid production, re- lation to nitrogenous compounds, chromogenesis, etc. Following the System of E. F. Smith, Bacterium of the Migula system becomes Aplanobacter: Pseudomonas becomes Bacterium; Micrococcus and Bacillus are unchanged. The significance of the generic names as recommended by the Committee of the Society of American Bacteriologists ^ is shown by the following abbreviated key: Typically filamentous; mycelium and conidia formed Actinomyces Typically unicellular forms Spherical cells; saprophytic forms; cells not in packets, not in chains; fermentative powers low; yellow pigment Micrococcus ^Winslow, C. E. A., Broadhurst, J., Buchanan, R. E., Krumwiede, C, Rogers, L. A., Smith, G. H. Final report of the committee of the Society of American Bac. teriologists on characterization and classification of bacterial types. Jour, of Bact- 5: 191, 1920. PLANT DISEASE FUNGI 15 Straight rods No endospores Regularly formed rods; metabolism not in- volving oxidation of carbon, hydrogen or their simple compounds or the fixation of atmospheric nitrogen. Flagella usually present, polar Pseudomonadacese Pseudomonas Flagella when present peritrichic. Bac- teriacese Not parasitic forms showing bipolar stain- ing; not strict parasites growing only in the presence of hemoglobin or ascitic fluid ; not water forms producing red or violet pigment. Plant pathogens Erwinia Not plant pathogens; Gram negative, forming H2 as well as CO2 if gas is produced Bacterium Endospores present Bacillaceae Aerobes Bacillus Types of Bacterial Disease in Plants. Bacteria frequently occur in plant disease as the cause of soft rot of large areas, as of fruits (cucumber, muskmelon), tubers (po- tato), leaves (lettuce, cabbage), stems and roots (carrots), or as soft rot of localized areas on fruits (drupes), or leaves (drupes, grains, bean, cotton, etc.). In nearly if not in all such cases the softening is mainly in parenchymatous tissue and is due to enzymes, produced by the bacteria, which dissolve the middle lamellae and thus free the component cells of the tissue from each other. In the early stages of such decay the causal organism alone may be present, but in advanced stages secondary bacteria or fungi may abound. Cankers of bark (pear, walnut) may dry out and be- come hard and the wood and cambium may be invaded by the bacteria. Another type of bacterial disease is that in which the bacteria invade the xylem, more rarely the phloem, of the veins (cucurbits, solanaceous plants, crucifers, corn, etc.) often completely filling many ducts to great distances. Wilting and death of the plant soon follows. In advanced stages of certain of these vascular diseases the bacteria may pass to the parenchyma and cause soft rot. 16 PLANT DISEASE FUNGI In case of bacterial soft rot or canker, bits of diseased tissue placed in a drop of water give off clouds of bacteria, usually ac- tively motile, plainly visible under the microscope. In many in- stances bacterial spots, particularly when on leaves, exhibit a translucent halo surrounding the center of disease. Such trans- lucence is always suggestive of a bacterial trouble but is of course merely suggestive. In case of vascular thrombosis cross section of a stem is often followed in a few moments by a viscous exudate from the severed Fig. 14 — Bacterial citrus canker enlarged and photographed by transmitted light to show translucent border. X 6. The tiny white specks are oil glands. (From "Bacterial Diseases of Plants" by Erwin F. Smith, W. B. Saunders Company, Publishers). ducts. This on microscopic examination proves to be bacterial. Thin sections of diseased vascular tissue, or cross sections of dis- eased stems, reveal the bacteria in the ducts or issuing in clouds from them. Observations such as these are useful in diagnosis. If bacteria in abundance are present and no fungi or other prob- able cause of disease is apparent the presumption is that the bac- teria are the etiological factor, though proof of this can rest only on evidence from inoculation by means of pure cultures. Another type of bacterial disease is afforded by tumor, such as the familar crown gall, so common on Rosaceous and many other PLANT DISEASE FUNGI 17 hosts (see pp. 38, 39). In this class of diseases the bacteria are present in comparatively small numbers and are very difficult of observation. Rathay's disease of orchard grass (see p. 21) gives still another type of disease. Some of the more prominent of the bacterial plant pathogens are listed below with the types of disease they cause. Italics in- dicate that this is chiefly the kind of disease produced by the or- ganism; other type that it is secondarily of this nature. Vascular disease. a. of xylem: Bad. stewarti, Ps. campestris, juglandis, phaseoli, solanacearum, B. inusce, atrosepticus, phytophthorus, tracheiphilus. b. of phloem: Bact. michiganense. Soft rot of parenchyma. a. general: Bact. teutlium, Ps. campestris, phaseoli, solana- cearum, B. carotovorus, atrosepticus, phytophthorus. b. local: Bact. stizolobii, Ps. angulata, avenae, lachrymans, maculicolum, malvacearum, pruni. Tumor : a. granuloma Ps. savastanoi b. teratoma Ps. tumefaciens. Surface parasitism: Bact. rathayi. Infection of plants by bacteria may occur either through wounds or through uninjured surfaces. Examples of the former are af- forded by Solanaceous plants, often invaded through broken roots; by bacteria entering through wounds produced by insects, e. g. : B. tracheiphilus, etc; by B. carotovorus which probably always en- ters through wounds. Examples of infection where entrance is not made through wounds are: the infection of tender delicate parts as blossoms, the organism entering through the nectaries (B. amy- lovorous) ; infection through water pores (Ps. campestris) ; through the stomata (Ps. malvacearum, Ps. pruni). The plant pathogens as yet known, with few exceptions, belong to the two genera Pseudomonas and Bacillus, between which they are about equally divided. In the earlier days of bacteriology and to some extent in recent days, bacteria have been seen in diseased plant tissues and have been placed by their observers in one genus or another and cited as the causes of the diseases in question but without actual evi- dence that they cause the diseases and very often without any real 18 PLANT DISEASE FUNGI evidence as to the genus to which the bacteria belonged. It is of course usually impossible to identify such forms and they must be dropped from consideration. Coccaceae (p. 14) Cells in free condition globular. No representative of this family, parasitic upon plants, has yet been reliably recorded in America, though several species of Micro- coccus have, on incomplete evidence, been assigned as the cause of plant disease in Europe. Bacteriaceae (p. 14) Bacterium Ehrenberg (p. 14) Aplanobacter E. F. Sm. Cells long or short, non-flagellate, cylindrical, straight, division in one direction. These non-motile forms, perhaps owing to their lack of power of locomotion, are comparatively rare as plant pathogens. Bact. stewarti (E. F. Sm.) E. F. Sm. i- ^ = Pseudomonas stewarti E. F. Sm. 1898, meaning polar flagel- late. = Bacterium stewarti (E. F. Sm.) E. F. Sm. 1905, meaning polar flagellate. = Aplanobacter stewarti (E. F. Sm.) McC. 1918, meaning non- flagellate. This species presents interesting complications in naming since it was first named Pseudomonas stewarti by Smith in 1898, fol- lowing the Migula system, and by him transferred to the genus Bacterium in 1905 abandoning Migula's genus Pseudomonas. In 1918 Miss McCulloch decided that the organism is devoid of flagella and named it Aplanobacter stewarti. Wishing to retain the Migula system I now call it Bacterium stewarti though with a different morphological significance than that conveyed by Smith when he first used this binomial. A medium size rod, 0.5-0.9 /x x 1-2 ji, with rounded ends, non- motile, viscid, aerobic. Yellow, non-liquefying; does not separate ^ McCulloch, L. A morphological and cultural note on the organism causing Stewart's disease of sweet corn. Phytop. 8: 441, 1918. 2 Smith. Bacterial Diseases of Plants. PLANT DISEASE FUNGI 19 casein in milk. T. D. P. 10 min., 53°. Agar colonies subcircular, no gas. The bacterial corn blight of this organism was first described by Stewart in 1897 and attributed to bacteria. The organism was originally described by E. F. Smith under the name Ps. stewarti in 1898 from a culture furnished by Stewart. Definite proof by Fig. 15. — Part of sweet-corn stem showing bundles occupied by Bact. stewarti. After Smith. inoculation of the causal relation of this organism to the disease was adduced in 1902 by sprinkling bacteria upon the leaves. Some plants showed typical constitutional symptoms during the first month, most of them in two or three months when the plants were 20 PLANT DISEASE FUNGI several feet high. In these plants the vessels became plugged with pure growths of Bact. stewarti f rom tip to base. Small holes filled with yellow slime appeared later in the parenchyma. Infection occurs chiefly through the stomata; wounds are entirely unneces- sary. Histological study shows the organisms in the seeds as well as in the ducts of diseased stems. Infection is mainly seed-borne. Bact. michiganense (E. F. Sm.) Stev. = Ps. michiganense (E. F. Sm.) Stev. Rod short with rounded ends, 0.35-0.4 x 0.8-1.0 fi, viscid, non- motile, aerobic; agar colonies yellow, smooth, round; gelatine slowly liquefied. The organism was described as the cause of a stem disease of tomatoes in Michigan. Bacteria were present in great numbers in Fig. in. — Bact. mirhigancnse showing effect as seen in cross section of a tomato stem. After Smith. the bundles; also in cavities in the pith and bark, the seat of the dis- ease being chiefly the phloem. The organism was isolated and the disease was produced both loy pure culture inoculations and by crude inoculations, using an impure inoculum. The disease pro- duced differs from that due to Ps. solanacearum in several ways, PLANT DISEASE FUNGI 21 particularly in that there is less brown stain in the bundles. It is highly infectious through above-ground parts. The disease spreads by stomatal infection. Bact. rathayi (E. F. Sm.) Stev. This organism is of interest because it first appears on the sur- face of the leaves and only in later stages is it found in the inter- cellular spaces and in the vascular tissue. The bacterium grows in thick, lemon-yellow, gummy layers enveloping the uppermost leaves and inflorescence. On orchard grass. Bact. agropyri is an organism that produces a similar disease on Agropyron. Bact. stizolobii (Wolf) Stev. Elements cylindrical with rounded ends, single or in pairs, 1-1.6 X 0.6-0.7 /z, non-motile, capsulate, no endospores, zoogloese not formed; neither acid fast nor stained by Gram's method; colo- nies on nutrient agar circular, raised, white, shining, margin en- tire or slightly undulate; gelatine not liquefied; casein partially precipitated and blue color in litmus milk intensified ; nitrates not reduced ; indol not formed ; neither acid nor gas formed in cultures with various sugars; no growth in closed arm of fermentation tubes; no diastatic action; pathogenic on foliage of velvet bean (Stizolobium), forming leaf spots which are at first translucent and become at maturity dark brown. Bact. teutlium Met. is reported as the cause of rot of beets. Several other species have been reported on various hosts abroad, notably on tomato, fig, vanilla, Wistaria, orchids, pine, and mul- berry. Pseudomonas Migula (p. 14) = Bacterium Cohn, emend E. F. Sm. Organism rod shaped, motile by 1-10 polar flagella, most com- monly one. Endospores are sometimes present. The cells in some species adhere to form short chains. The basis of separation into species is the growth upon gelatine, character of the colonies, chromogen- esis and numerous other cultural characters. Numerous species occur as plant pathogens. Ps. angulata (Fromme and Murray) Stev.^ A short rod, 0.5 x 2-2.5 yu, no spores, no capsules, motile by 3-6 ^ Fromme, F. D. and Wingard, S. A. Black fire or angular leafspot of tobacco. Va. Agr. Exp. Sta. Tech. Bull. 25, 1922. 22 PLANT DISEASE FUNGI flagella. Gram negative, aerobic. Agar colony smooth, shiny, opal- escent then dull white, gelatine liquefied. On tobacco leaves causing spots, usually vein-limited, irregu- larly angular, centers tan, surrounded by a translucent zone, border darker. Ps. apii Jagger ^ A short rod, 0.44-0.87 /x x 0.87-1.74 /x, one to several polar flagella; colonies on nutrient agar grayish white, shiny, circular, edges entire, flat to slightly raised, granular with age ; gelatine liq- uefied, litmus milk becomes more alkaline, casein peptonized with- out formation of curd; acid formed from glucose and saccharose, alkali from lactose and glycerine, no gas; no growth in closed arm of fermentation tubes; nitrates not reduced. Parasitic on leaves in celery. Ps. aptata (Brown and Jamieson) Stev.- A short motile rod with rounded ends ; flagella bipolar ; no spores or capsules, aerobic. Agar colonies smooth, whitish; bouillon clouded, gelatine liquefied, fluoresence greenish. T. D. P. 47.5-48°. Gram negative. On nasturtium (Tropoeolum) and sugar beet leaves causing leaf spots. On nasturtium the spots are brownish and water-soaked, 2-5 mm. in diameter. On beets the spots are irregular, dark brown, often black. The organism was isolated in pure culture from both hosts and from either host produced the disease on both hosts. It is also infectious to bean, lettuce, pepper and egg plant. It ap- pears chiefly to enter through wounds and the bacteria are found in large numbers within the cells. The cell walls become ruptured and collapse. Ps. atrofaciens (McC.) Stev. Rods 1-2.7 X 0.6 /x, often in long filaments, motile by 1-4 polar flagella, aerobic, no spores, capsulated on beef agar. Peptone-beef agar colonies smooth, shiny white becoming greenish, medium turned green. Gelatine liquefied, milk not coagulated. Gram negative. On wheat causing lesions at the base of glumes and kernels. Inoculations are followed by glume discoloration in four days. The discolored tissues abound in bacteria, which penetrate even into the kernels. ^ Jagger, Ivan C. Bacterial leafspot disease of celery. Jour. Agr. Res. 21: 185, 1921. ^ Brown, Nellie A. and Jamieson, Clara O. A bacterium causing a disease of sugar beet and nasturtium leaves. Jour. Agr. Res. 1: 189, 1914. PLANT DISEASE FUNGI 23 Ps. avenae Manns. A short rod with round ends, 0.5-1 n x 1-2 jjL. Actively motile, generally by one polar flagellum, occa- sionally by two or three. Gram negative. What seem to be endo- spores are found in old cultures. On agar stroke, growth very slow, filiform, rather flat, glistening; margin smooth, opaque to opales- cent; non-chromogenic. Liquefaction occurs on gelatine in seven to twelve days. Broth is slowly clouded; agar colonies amorphous, round with surface smooth, edges entire, no gas in dextrose, sac- charose, lactose, maltose, or glycerine; ammonia and indol not formed; nitrates reduced to nitrites. T. D. P. 10 min., 60°, Opt. 20° to 30°. This organism was isolated and described by Manns in 1909, as the cause of a serious oat blight. Inoculations with it alone by hypodermic injection produced only limited lesions but similar inoculations with a mixed culture of Ps. avenae and Bacillus avense produced typical dis- ease. Manns, moreover, noticed that the virulence of the Pseudomonas de- creased when kept in culture free from the Bacillus, also that in the disease as it occurs in nature these two organ- isms are associated. His conclusion is that the Pseudomonas is the active parasite and that the Bacillus is an im- fig. i?.— ps. av.nce. After Manns. portant, perhaps a necessary symbiont. Infection in nature is chiefly stomatal by spattering rain. Soaking of seed in suspensions of bacteria did not produce the disease. Inoculations on wheat failed, though from one variety of blighted wheat, Extra Square Head, the typical organism was isolated. Inoculations on corn made during wet weather produced lesions which spread rapidly and the organism was re-isolated. Barley is said by Manns to be susceptible and what he believes to be the same disease occurs on blue grass and timothy. Ps. beticola (Sm. Br. & Town.) Stev. causes a disease of beets, in superficial appearance like crown gall. Ps. campestris (Pam.) E. F. Sm. A rod-shaped, motile, organ- ism generally 0.7-3.0 x 0.4-0.5 /i; color dull waxy-yellow to canary-yellow, occasionally brighter or more pale. One polar flagel- lum; no spores known. Aerobic but not a gas or acid producer, gelatine liquefied. Cavities are formed around the bundles but the 24 PLANT DISEASE FUNGI Fig. 18. — Showing effect of inoculation of Ps. campestris into cabbage plants. Nos. 1 and 2 six weeks after inoculation. No. 3, check plant uninoculated. After Russell. Fig. 19. — Ps. campestris. Section of a cabbage leaf parallel to the surface and near the margin, showing the result of in- fection through the water pores. After Smith. PLANT DISEASE FUNGI 25 organism seems to be only feebly destructive to cellulose. A brown pigment is produced in the host plants and on steamed cruciferous substrata. Growth rapid on steamed potato cylinders at room temperatures, without odor or brown pigment. Growth feeble at 7°, rapid at 17 to 19°, luxuriant at 21 to 26°, _owa^^.¥^?^&^^^^S<^^^^^^ very feeble at 37 to 38°, and ceases at 40°. T. D. P., 10 min., 51°. It is troublesome upon cabbage, turnips, cauliflowers, collards and a very large num- ber of cruciferous hosts, both cultivated and wild, are suscep- tible. The chief seat of in- fection is the ducts which become filled with the bacteria and are blackened. This organism was first isolated by Pam- mel from rutabagas and yellow turnips in 1892; green-house in- oculations with pure cultures were made in scalpel wounds, which were then sealed with wax. The plants showed rot in a few days and the actual causal relation of the organism was thus established. It cabbage and turnip organisms are K# Fig. 20. — Cross-section of turnip root showing vessels filled with Ps. campestris. After Smith. was later shown that the identical and that the bac- teria, by solution of the cellulose, produce pits and holes through the walls of the host cells resulting eventually in large cavities. Dissolution of tissue is accomplished chiefly by occupation of the 26 PLANT DISEASE FUNGI intercellular spaces followed by solution of the middle lamellae and finally by squeezing the elements apart. Infection is chiefly through the water pores or through wounds made by insects ; the bacteria being air or insect borne and derived largely from infected soil. After entering the plant the bacteria multiply rapidly, and migrate in every direction by means of the veins. The organism can survive the winter on the seed and thus infect seedlings. Ps. cannae (Bryan) Stev.^ A short rod with rounded ends; flagella 1-3, bi-polar; capsules present; no pseudozoogloe?e, aerobic, non-chromogenic, liquefies gelatine very slowly, does not produce acid or gas from sugars; clears milk; blues, then reduces litmus milk without coagulation, does not produce indol. Optimum temperature 35° C, maximum 40°, minimum 5°; T. D. P. 52°. Gram negative. The cause of meristematic disease in cultivated cannas. Ps. cerasi Griffin - Short rods 1.5-2.5 x 0.5-0.8 ix, motile by 1 or 2 polar flagella, no spores. Gram negative. On agar, flat, glistening, greening the medium; gelatine liquefied. The cause of blight of buds and fruit spurs of cherry accom- panied by gummosis; also of girdling of limb or trunk. Ps. citrarefaciens (Lee) Stev."^ A rod with 1-4 polar flagella. It causes " Citrus Blast " in which the young leaves drop off. Ps. citri Hasse A short motile rod with rounded ends and one polar flagellum, 1.5-2 X 0.5-0.7 u. Agar colonies circular, entire, smooth, dull yel- low. On potato a bright yellow streak, slimy. Casein precipi- tated, gelatine liquefied. On citrus causing canker also fruit and leaf spots. Infection is produced with or without wounds by means of pure cultures. The host cells are stimulated to abnormal growth and the tension rup- tures the epidermis. Diseased cells are filled with the bacteria. The distinction between palisade and parenchyma is obliterated and all the cells are somewhat enlarged and distorted. In later ^ Bryan, Mary K. A bacterial budrot of cannas. Jour. Agr. Res. 21: 143, 1921. ^ Barss, H. B. Cherry gummosis. Ore. Agr. Exp. Sta. Crop Pest and Hort. Rept. 199. 1911-1912. ^ Lee, H. Atherton. A new bacterial citrus disease. Jour. Agr. Res. 9: 1, 1917. PLANT DISEASE FUNGI 27 stages some of the cells disintegrate. Bacterial action is more pro- nounced on the cell contents than on the walls. Ps. citriputealis (CO. Sm.) Stev.^ Active^ motile rods with a single polar flagellum, 2-4 x 0.5-1 m, aerobic, no capsule or spores. Agar colonies pearl gray, 2-5 mm., gelatine slowly liquefied. Circular, black, depressed, dry-rot spots, 5-20 mm. in diameter, are produced in the rind of lemons; inocula- tions were made with pure cultures by pricking and by atomizing, spots resulting in three or four days. Fig. 21. — Section of a portion of a grapefruit leaf bearing a young canker caused by Ps. citri. After Hasse. Ps. coronafaciens (Elliott) Stev.- Rod, 2.3 X 0.65 ii, motile by polar flagella, no spores, capsulate; agar colonies white, gelatine liquefied slowly, casein digested with- out curdling. Gram negative. Pathogenic in oats and to less extent on wheat, rye, and barley. Spots ovate, chlorotic, 0.5-2 cm. or larger. Centers of gray-brown, collapsed tissue surrounded by a halo, at first light green, later yel- low. Bacteria present in the centers, probably absent from the halo, at first intercellular but later they destroy the cell walls and cause collapse. Ps. flaccumfaciens (Hedges) Stev. causes disease of beans. Ps. dissolvens Rosen Short rods, motile by means of a single polar flagellum, cap- sules present, no spores, white on most solid media; colonies round, margins entire, white, opaque, glistening, emitting a strong odor of decaying vegetable matter; gelatine not liquefied; acid and gas produced on most nutrient media. It is the cause of rot of the roots of corn and of adjacent stem with purplish discoloration. 1 Smith, C. O. Black pit of lemon. Phytop. 3: 277, 191.3. 2 EUiott, C. Halo blight of oats. Jour. Agr. Res. 19: 139, 1920. 28 PLANT DISEASE FUNGI Ps. vesicatoria (Doidge) Stev.^=Bact. exitiosum Gardner & Kendrick. Cylindrical rods, rounded at the ends, solitary or in pairs; in- dividual rods 1.5-2.7 x 0.6-1.3 n; motile by a single polar flagel- lum; aerobic, no spores; superficial colonies on potato agar, round, pulvinate, smooth, glistening, naphthalene yellow, with radial striae of color in peripheral zone; margin entire. Gelatine rapidly liquefied; no acid produced in milk; digests casein; Gram negative. The cause of a spot disease in fruit, stem and leaves of tomato. Ps. erodii Lewis is described as pathogenic on Erodium and a large number of varieties of cultivated "geraniums." Ps. fluorescens (Flligge) Mig. or varieties of it are held responsi- ble for a decay of celery, and of producing wet rot of various vege- tables, carrots, rutabagas, tobacco, tomatoes, melons. A disease of mushrooms is also caused by this or a very closely related organism. Ps. glycinea Coerper Rods 2.3-3 X 1.2-1.5 jj,, motile by 1-several polar flagella; no spores; capsulated on blood agar. Potato agar colonies round, shiny, with umbonate center, creamy to brownish. No gelatine liquefaction, casein not digested. Gram negative. T. D. P. 48-49°. Forming small angular lesions on soy bean. Young spots are translucent, old are dark reddish-brown to black. Spots 1-2 mm. in diameter, often confluent. Infection is stomatal, the bacteria invading the parenchyma intercellularly. Inoculation by atomiz- ing unwounded leaves gives spots in about 10 days. A closely related organism was described by Wolf under the name Bact. sojae as the cause of a similar disease of soy beans. Ps. juglandis Pierce. A rod 1-2 x 0.5 fj,, with rounded ends, ac- tively motile by one long polar flagellum. Bright chrome-yellow ingrowth; disastatic ferment present. No gas; aerobic. It was iso- lated from diseased nuts, leaves, and twigs of English walnut in California in 1901. Inoculations by spraying demonstrated its pathogenicity. The organism is closely related to Ps. campestris but is distinguished from it by the abundant, bright yellow pig- ment produced upon the surface of extracts of leaves of walnut, magnolia, fig, castor bean and loquat. In young walnuts the epicarp, forming shell and kernel, are destroyed. Leaves are attacked along the veins and on the pet- ^ Gardner, Max W. & Kendrick, James B. Bacterial spot of tomato. Jour. Agr. Res. 21: 123, 1921. PLANT DISEASE FUNGI 29 ioles, the bacteria often entering the vessels. All tissues in branches are destroyed, the bacteria entering and wintering in the pith. Infection is stomatal. Ps. lachrymans. (Sm. & Bryan) Carsner. Rod 0.8 x 1-2 fx, with rounded ends, motile by 1-5 polar flagella, aerobic, non-spor- ing. Gelatine slowly liquefied. Agar surface colonies circular, white, no gas. Gram negative. On cucumber leaves forming angular, water soaked, exudating spots. Infection of the leaves and fruit is through the stomata and occurs more readily when the stomata are open. Small spots result in about five days. In these the bacteria occupy the intercellular spaces, and crowd apart and crush the parenchyma, causing swelling and exudation. In age the diseased area becomes dry, brown and dead. Ps. maculicola (McC.) Stev. A short rod, forming long chains in some media. Ends rounded. Size from leaf 1.5-2.4 fx x 0.8-0.9 yu; in 24-hour beef-agar culture, 1.5-3 fx x 0.9 fx. No spores, actively motile, one to five polar flagella, two to three times the length of the rod. Motile in most artificial media. In- volution forms in alkaline beef bouillon. Pseudo-zoogloese in Uschinsky's solution. Gram negative. Stains readily with carbol- fuchsin and with an alcholic solution of gentian violet. Agar plate colonies visible on the second day as tiny white specks, in three to four days, 1-3 mm. in diameter, white, round, smooth, flat, shining, and translucent, edges entire, with age dull to dirty white, slightly irregular, edges undulate, slightly crinkled, and with indistinct radiating marginal lines. Buried colonies small, lens-shaped. Agar streak cultures white, margins slightly undulate. Beef bouillon clouds in twenty-four hours. Growth best at surface where a white layer, not a true pellicle, is formed. No zoogloea); no rim. Gelatine stab cultures liquefied in eight to ten days. Growth from surface crateriform; slight, white, granular precipitate. Slight green fluorescence. No separation into curd and whey. Indol production feeble. T. D. P. 46°. Opt. 24-25°. Max. 29°. Min. below 0°. Isolated from cauliflower leaves on which it forms brownish to purplish-gray spots 1-3 mm. in diameter. Pathogenicity on this host also on cabbage was proved by atomizing. Its entrance is stomatal, and specks 1-3 mm. in diameter in the green leaves, result, both on the veins and in the parenchyma. 30 PLANT DISEASE FUNGI Ps. malvacearum E. F. Sm. This yellow organism, pathogenic on cotton, much resembles Ps. campestris but its slime is more translucent on potato and it does not attack the cabbage. It is Gram negative, non-acid -fast, non-sporing, motile and polar flagellate. It was grown in pure culture and successful inocula- tions were made by atomizing a sus- pension of a young agar culture of the organism upon cotton leaves and bolls. Infection is largely stomatal, the inter- cellular, substomatal spaces becoming filled with bacteria. Minute water- soaked spots result in from 12-20 days. Ps. marginalis (Brown) Stev. A short rod, motile by 1-3 bipolar fla- gella, capsulate, no spores, aerobic. Agar colonies cream colored, later yel- low. Agar colored green. On potato dirty-cream colored, later buff. Gela- tine liquefied, fluorescence green. T. D. P. 52-53.° On lettuce causing marginal brown to black dead spots which become dry and papery. Ps. medicaginis Sackett. A short rod, 1.2-2.4 x 0.5-0.8 ju; filaments ^'sta''-;^?torairSSSn ifat 20.2-37.2 M long. No spores; actively imrth^''''^ ^^°^ °^ ''°"°'^' ^^^"""^ motile with 1-4 bipolar flagella; capsules and zoogloese none. Agar streak filiform later echinulate, glistening, smooth, translucent, grayish-white; no gelatine liquefaction; bouillon slightly turbid, pellicle on third day, sediment scant. Milk unchanged. Agar colonies round, grayish-white. No gas or indol. Optimum reac- tion + 15 to + 18. Fuller's scale. T. D. P. 49-50°, 10 min. Opt. 28-30°. Aerobic. No diastase, invertase, zymase, rennet or pepsin. It occurs as a pathogen on alfalfa and issues in clouds visible to the naked eye from small pieces of tissue of the diseased stem or leaf when mo'unted in water on the slide. These clouds under the high power resolve into actively motile rods, relatively short and thick. The bacteria are also found in practically pure culture in J^BWiMltH PLANT DISEASE FUNGI 31 the exudate which oozes from the diseased tissues as a clear viscous hquid and collects in drops or spreads over the stem. In early stages the stem is watery, semi-translucent. In late stages disease extends to the center of the stem and the interior is brown. Dis- ease also occurs on petioles and leaves. Sackett with pure culture inoculations produced the typical disease and re-isolated the or- ganism with unchanged characters. Re-inoculated, it again caused disease. Infection, stomatal or water pore, was also secured through the apparently unbroken epidermis. It is believed that the usual mode of infection is through rifts in the epidermis due to frost and that the germ is wind-borne from infected soil. Ps. mell e a Johnson. A short rod with rounded ends. Average size 0.6 X 1.8 M. Motile by a tuft of polar flagella usually two to three in number, three to five times as long as the body of the organism. No spores or involution forms observed. Capsules present. It is Gram-negative and not acid-fast, pale or orange yellow on most media. In gelatine stabs growth is best at top with hquefaction beginning in 3 days and complete in about 20 days. Coagula- tion of milk is prompt. Parasitic on tobacco causing leaf spots. The leaf spot of tobacco differs from both the wildfire leaf spot and the angular leaf spot and manifests itself by round, brown, or rust-colored spots, usually less than a half inch in diameter, but frequently running together to form larger irregular lesions. Frequently the young Fig. 23. — Ps. medicaginis; agar colonies 7 days old, deep and surface colonies by reflected light. After Sackett. 32 PLANT DISEASE FUNGI lesions are marked by a distinct chlorotic area or halo surrounding the point of infection. Ps. mori (B. & L.) Stev. Rod with rounded ends, 1.8-4.5 x 0.9-1.3 fjL, mostly 3.6 x 1.-2 /jl; motile by 1-7 polar flagella. No spores. Pseudozooglcese present. Agar colonies round, smooth, flat. Agar streaks spreading, flat, dull-white. Gelatine stab fili- form, no liquefaction. Milk not coagulated. No gas. T. D. P. 51.5°. This organism causes a blight of mulberries much resembling pear blight. The bacteria invade both wood and bark though disease is principally of the bark. On the leaves water-soaked spots form and eventually turn dark. Bacteria are in the inter- cellular spaces and produce cavities. In 1894 Boyer and Lambert produced successful inoculations on mulberries with an organism to which they gave the above name, but without description. In 1908 E. F. Smith plated out, from bHghted mulberry leaves collected in Georgia, a white species with which he made numerous infections on both stems and leaves of mulberry. From these cultures Smith supplied the description quoted in part above. Ps. papulans Rose causes rough-bark or scurfy bark of apples. Ps. pelargoni (Brown) Stev. A motile rod with one polar flagel- lum causes a bacterial leaf spot disease of the cultivated geranium. Ps. phaseoli E. F. Sm. A short, round-ended rod, wax-yellow to chrome-yellow, motile, polar-flagellate, anaerobic. Milk coagu- lates, and the whey slowly separates without acidity; gelatine liquefies slowly. Growth feeble at 37°, none at 40°. T. D. P. 10 min., 49.5°. A starch enzyme is produced and the middle lamella also dis- -^ . solved. 7 \ This organism is pathogenic to beans and j some related legumes and is closely related to Ps. campestris; a variety of it has been described ^"'' AftTr^Smfth^'^"^'' on soy bean. The disease on leaves, stems and pods is principally of the parenchyma though ducts are occasionally invaded to a distance of several centi- meters. On leaves a few days after infection minute translucent dots appear; these enlarge and, due to collapse of the tissues, be- come sunken. On pods the fleshy pericarp is rotted; the bac- teria infect the developing seed and surface bacterial ooze is present. Infection is largely stomatai. PLANT DISEASE FUNGI 33 Ps. pisi Sackett. A short rod, 1.11-3.28 x 3.28 x 0.58-0.82 ^, no spores, no capsule, no zoogloese, motile by one polar flagellum. Gram negative, Agar stroke filiform, grayish- white. Gelatine liquefied. Milk coagulated, later peptonized. On garden peas. The affected stems are watery olive green to olive brown, attacked petioles soon assume the same color and collapse. Infection is by way of stomata or wounds. The sub- stomatal chambers are crowded with bacteria, also many of the adjacent cells. Inoculation and reisolation establish the path- ogenicity of the organism. Ps. pruni E. F. Sm. The organism resembles Ps. campestris but is distinguished from it by its feebler growth on potato and Fig. 25. — Earliest stage of fruit spot on green plums, due to Ps. pruni. The bacteria entered through the stoma. After Smith. by its behavior in Uschnisky's solution which it converts into a viscid fluid. It consists of small rods, motile by one to several polar flagella. T. D. P. 51°. On apricot, nectarine, peach and plum, causing leaf, twig and fruit disease. The bacteria enter through the stomata or lenticels and cause 34 PLANT DISEASE FUNGI watery spots on green fruit and leaves, and finally the death of the affected tissue. Cankers are also produced on the twigs. In earli- est disease the infection is limited to the substomatal space, but gradually invades more distant tissue. Parenchyma is chiefly af- fected, but phloem and xylem are also attacked. By numerous cultures and cross inoculations it was proved that this organism is responsible for the disease. Ps. rhizoctonia (Thomas) Stev. A rod shaped organism, not motile, colony circular, olive buff in color when incubated in the dark, pyrite yellow in subdued light. Does not stain by Gram's method, not acid-fast. Gives good re- duction of nitrates within 24 hours. Characteristic color constant on all ordinary media such as potato agar, plain nutrient agar, potato plugs, rice, oatmeal agar. It causes retarded development or a rosette disease of lettuce accompanied by a yellowing or flaccid condition of the outer leaves. The small fibrous roots are apparently attacked first at their tips. The infection slowly progresses upward until the larger roots are invaded. No rot or spots upon the leaves or stems. The chief role of the organism seems to be to attack the root hairs and small fibrous roots of the lettuce plant, gain entrance into the vas- cular system and interfere with the free passage of materials. Ps. savastanoi (E. F. Sm.) Stev. A rod with rounded ends, solitary or in short chains, 1.2-3 x 0.4-0.8 fi; motile, aerobic, non- sporing, flagella 1-4, polar. Standard agar surface colonies, white, small, circular, smooth, 1.5-3 mm. at three days, edge entire; bouil- lon thinly clouded, precipitate slight, white. On gelatine no liq- uefaction; colonies white, round, erose, margin pale. From tubercles on Californian olive branches, the causal organ- ism, which is in part Ps. olese-tuberculosis Sav. and which may bear relation to several other olive bacteria previously described in Europe, was isolated. The organism when inoculated by puncture into young olive shoots produced the characteristic tubercle. Later it was re-iso- lated from these artificially produced tubercles and used in a second series of inoculations which gave a second crop of tubercles. The oleander was not susceptible to infection though a similar tumor occurs on this host. A like disease is also on ash but the causal organism is slightly different. This organism causes marked hypertrophy on roots, trunk, PLANT DISEASE FUNGI 35 branches and leaves of olives, resulting in tumors, large or small, spongy or cheesy, which soon decay. The disease is perennial and spreads yearly into both new and old wood. Secondary tumors occur near or distant from old ones, but without connecting strands. The bacteria are abundant between the host cells and later in the intercellular spaces where they develop irregularly branched cavities. Infection may occur from the surface through wounds or from the interior by migration of bacteria through the ducts. Such ducts are browned and somewhat disorganized. The tumor may consist of both wood and cortex, the vessels being re- duced and the parenchyma greatly increased. Ps. solanacearum (E. F. Sm.) Stev.i= Bacillus solanacearum E. F. Sm.= Bact. solanacearum (E. F. Sm.) E. F. Sm. A medium sized, easily stained, strictly aerobic bacillus with rounded ends; about 1^-3 times longer than broad; 0.5 x 1.5 fx. Motile, slug- gish or active; flagella polar. Spores not known. Zoogloese 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 who made inoculations which produced the disease, but he did not use pure cultures. In its hosts the bacillus is found in the pith, in the xylem which is browned, and more rarely in the bark. It is, however, primarily a vascular disease and from the cut ends of infected ducts bacteria exude as a viscid ooze. The diseased ducts are browned and may be traced to great distances through the plant, even from root to leaf. From the bundles the organism later invades other tissues, often with great destruction of pith and bark, honey- combing the pith with cavities. Infection is commonly through wounds, often by way of broken roots, but is sometimes through stomata. Needle prick inoculations in tomatoes by Smith, with pure cul- tures, were followed after several weeks by typical disease. Inocu- lations in Irish potato resulted similarly, though in this host the parenchjona and bark were eventually invaded, and the tuber ^ Smith, E. F. Bacterial diseases of plants. 36 PLANT DISEASE FUNGI was reached through its stem end and rotted. In South CaroHna, Smith noted the disease on egg plants and crude cross inoculations were made in tomato. He demonstrated experimentally the effi- ciency of the potato beetle in transmitting the disease. The disease was described for tobacco by Stevens and Sackett. Successful inoculations were reported upon tobacco by E. F. Smith in 1909. In addition to the above hosts it is known to grow upon Fig. 26. — Ps. solanacearum: cross-section of a potato stem showing bacteria in the ducts. After E. F. Smith. Datura, Solanum nigrum, Physalis and Petunia, nasturtium, pea- nut, bean, pea, Ricinus, vanilla, Helianthus, Dahlia and Cosmos. B. nicotianse Uyeda, said to cause a wilt of tobacco in Japan closely resembling that caused by Ps. solanacearum, may be this same organism. Ps. tabaci (Wolf and Foster) Ste^^ Rod motile by 1 polar flagellum, 2.4-5 x 0.9-1.5 n, Gram nega- tive. Potato agar colonies gray-white, circular. Gelatine lique- faction slow. T. D. P. 65°. On tobacco leaves producing water-soaked spots, at first chlo- rotic, 0.5-1. cm. in diameter. Brown, dead areas soon develop PLANT DISEASE FUNGI 37 in the centers. Bacteria abound in the intercellular spaces and in old lesions within the cells. Ps. translucens J. J. & R. Rods 0.5-0.8 X 1-2.5 fx, motile by one polar flagellum, aerobic, no spores. Agar colonies entire, smooth, shiny, wax-yellow. Gel- atine slowly liquefied, casein digested. Gram negative. On barley leaves causing translucent spots. The leaf spots are watery, extend longitudinally, and are largely vein-limited. Infected tissues later become yellow, then brown. Bacterial exudation occurs under humid conditions and the exu- date dries to resinous granules. Infection is stomatal and the bac- terial invasion is in the parenchyma, largely through the intercel- lular spaces; the cell walls disintegrate. Ps. translucens var. undulosa causes black chaff of wheat in which black sunken stripes, swarming with bacteria, occur on the glume. In late stages the rachis and stalk are also striped. Ps. tumefaciens (S. & T.) Stev. Vegetative cells taken di- rectly from a gall usually 0.6-1.0 fx x 1.2-1.5 fi. Endospores not observed; motile by means of one, sometimes two or three terminal flagella; viscid on agar; readily stained in ordinary basic anilin stains. Gram, negative; agar surface colonies, white, smooth, circular; margin even, shining, semi- transparent, maximum size 2 to 4 mm.; agar streak growth moderate, filiform; on sterile potato cylinders growth more rapid, in one or two days covering the entire surface of the cylinder; smooth, wet-glistening, slimy to viscid, odorless; potato cylinder grayish, darker with age, never yellow; gelatine colonies dense, white, circular; small, non-lique- fying, medium not stained; in beef broth clouding often absent or incon- spicuous, rim of gelatinous threads present, also more or less of pellicle; milk coagulation delayed; litmus milk gradually blued, then reduced; no gas produced; organism aerobic in its tendencies; nitrates not reduced; indol produced in small quantity, slowly. T; D. P. 51°. Opt. between 25° and 28°, Max. 37°. Growth occurs at 0°. Milk, bouillon, dextrose peptone water with calcium carbonate are the best media for long continued growth. ^^p*^ 0^ '^ ^. & -^d Fig. 27 — Flagella of Ps. tumefa- ciens. After Smith. 38 PLANT DISEASE FUNGI The cause of crown gall on a wide range of hosts. In galls on the Paris daisy these bacteria were found in small numbers. By plating they were obtained in pure culture and punc- ture inoculations repeatedly resulted in the characteristic gall. From these the organism was re-isolated and the disease again produced, thus giving conclusive evidence that the organism is the actual cause of the gall. Swellings began four or five days after inocu- lation and in a month they were well developed, though they continued to enlarge for several months, reaching a size of 2-5 cm. in diameter. The disease produced is peculiar in that the cells at- tacked are not killed but are stimulated to multiply, the result being a largely hyper- plasied parenchyma, poorly supplied with vessels, forming either a hard or a soft tumor which varies in size up to more than four feet in diame- ter. Secondary tumors de- velop at various, often consid- erable, distances from the primary tumors and are con- nected with them by a con- tinuous chain of diseased cells, the tumor strand. The sec- ondary tumors have the tissue structure of the region in which the primary tumor is located, e. g., if the primary tumor is in a stem and the secondary tumor in a leaf the secondary tumor will have the structure characteristic of stems. The causal organism occurs in small numbers inside of the host cells and as the cells divide bacteria go to each daughter cell. They are difficult to see when in tissues and require special stains. Tumor-producing Schizomycetes have been isolated from over- FiG. 28. — Cross-aection of stem between pri- mary and secondary tumors, showing large- celled tumor-strand with big nuclei. After E. F. Smith. PLANT DISEASE FUNGI 39 growths on plants lielonging to many widely separated families (Compositae to Salicacese) and galls have been produced by inocula- tion, using the daisy and hop organism, on some 40 kinds of plants belonging to 18 families. Natural galls have been studied on Chrysanthemum, peach, apple, rose, quince, honeysuckle. Arbu- tus, cotton, poplar, chestnut, alfalfa, grape, hop, beet, salsify, tur- nip, parsnip, lettuce, and willow. The organisms from these sources are closely alike on various culture media, and many of them are readily cross-inoculable, e. g., daisy to peach, radish, grape, sugar-beet, hop; peach to daisy, apple, Pelargonium, sugar- beet, poplar; hop to daisy, tomato, sugar-beet; grape to almond, sugar-beet; poplar to cactus, oleander, sugar-beet; willow to daisy. In general it is said that all plants susceptible to crown galls, i. e., those on which the galls have been found in nature, are susceptible to artificial cross inoculation. Hard gall, hairy root, and soft gall are also all due to infectious bacteria. Smith states that the hairy root organism and the crown gall organism are identical and that if infection takes place in certain tissues an ordinary gall will develop, while if other tissues are first invaded, then a cluster of fleshy roots will develop. Ps. vignae Gardner & Kendrick causes a rather destructive bacterial disease of cowpeas characterized by spots on the leaves, stems and pods. Ps. viridilivida (Brown) Stev. Rod motile, by 1-3 polar flagella, gelatine liquefied slowly. On potato cylinders a fleeting dark blue-green color. Gram posi- tive. Agar colonies round, entire, smooth, cream-white. On lettuce leaves producing spotting. The bacteria are both in the cells and between them. Ps. vitians (Brown) Stev. A short rod motile by bipolar flagella, capsulate, no spores, aero- bic. Agar colonies, light-cream color, smooth, thin, round. On po- tato yellow. Gelatine liquefied. Gram negative. T. D. P. 51-52°. On lettuce leaves producing spots and rot and in stems produc- ing rot. Ps. woodsii (E. F. Sm.) Stev. causes spots on carnation leaves, infection occurring through the stomata. Other species have been reported on iris, gladiolus, hyacinth, syringa, sugar-cane, Lima bean, clover.^ Mones, L. R., Williamson, M. M.. Wolf, F. A., McCuUoch, Lucia. Bacterial leafspot of clovers. Jour. Agr. Res. 25; 471, 1923. 40 PLANT DISEASE FUNGI Bacillus Cohn (p. 14) This genus differs from Pseudomonas only in its peritrichiate, not polar, flagella. Endospores are often present. Of the four hundred and fifty or more species fourteen are given here as plant pathogens. Numerous animal pathogens also belong to this genus, notably B. typhosus, B. pestis. B. amylovorus (Burr.) Trev.= Erwinia amylovora (Burr.) Com- mittee. Bacillus in broth, 0.9-1.5 x 0.7-1.0 m, longer when older. Gram negative; no capsule; flagella several, peritrichiate; no spores; broth clouded, pellicle slight. Gelatine shows slow, crateriform lique- faction; agar buried colonies white, surface colonies elevated, circular, wet-shining, margin irregular; milk coagulated in three- fourths of a day, later digested to a pasty condition. Opt. 25-30°. T. D. P. 43.7°, 10 min. Facultative anaerobe. Indol produced; no gas; no pigment. Bacteria were noted in blighted pear twigs by Burrill in 1877. In 1880 he demonstrated the communicability of the disease by introducing the bacterial exudate into healthy 7^"^^ pear trees as well as into apple and quince trees. This constitutes the first case of plant disease definitely attributed to bacteria. Burrill's results were confirmed by Arthur in 1884 by one hundred and twenty-one puncture inoculations, using the exudate, also a bacterial suspension from diseased twigs. He further demonstrated the susceptibility of Juneberry and hawthorn. ^^oru?n^itipiying^°by Arthur placcd the whole matter on a firm fission- After Whet- foundatlou by passing the bacteria through a long series of artificial cultures and then by inoculations, showing that they w^ere capable of causing the blight. He further demonstrated that the bacterial exudate from the tree, when freed of bacteria by filtration, could not produce disease. The results of an extensive study of the bacteria on various media, of their morphology and stain reactions, were published by Arthur in 1886. Bacteria were shown to penetrate twigs 3-4 dm. beyond their area of visible effect. In 1902 Jones isolated an organism from blighted plum trees. This he demonstrated by culture and cross inoculation in fruits to be identical with the pear blight organism, though inoculations in PLANT DISEASE FUNGI 41 plum twigs did not give disease, presumably due to the high resist- ance of this plant. Similarly Paddock has shown this organism to attack the apricot. Other hosts are hawthorn, shad bush, mountain ash, loquat, strawberry and cherry, and possibly the blackberry. By inoculations with pure cultures of the apple body-blight bacteria, blight upon twigs and blossoms was produced by Whetzel in 1906 thus proving the identity of these two forms of disease, an identity asserted first by Burrill. The bacteria enter the host either through wounds or through the nectaries. The first evidence of infection is a transparency of the diseased tissue, probably due to removal of air from the in- tercellular spaces, later followed by browning. The bacteria abound in the spaces between cells also in the ducts, and in late stages of disease the host cells are plasmolyzed. In the shoots disease is chiefly of the bark and it advances through the bark parenchyma. The organism disintegrates fruits by multiplying in the intercel- lular spaces and dissolving the middle lamellae. B. atrosepticus van Hall.^- ^ Short rods, long rods, short chains, long chains, 0.4-0.8 x 1-2 iJL or more. Endospores none; flagella few, not over 6 or 8. Attachment peritrichiate; capsules none. Agar stroke filiform, flat to slightly raised, luster glistening, surface smooth, slightly but distinctly bluish opalescent, pearly-white. Gelatine liquefaction, infundibuliform to slightly napiform, or saccate. This organism is said by Morse to cause potato black-leg and to be identical with B. solanisaprus Harr. and to be distinct from B. phytophthorus Appel. See p. 45. B. avenae Manns. This is the symbiont of Pseudomonas avenge. See p. 30. A very actively motile bacillus, short, rod-shaped with rounded ends, 0.75-1 x 1.5-2 fi. Gram negative; endospores not ob- served; flagella man\^, diffuse, long, undulate; growth on agar stroke rapid, filiform, white, glistening, later somewhat dull, mar- gin smooth, growth rather opaque, turning yellow third day; gela- tine not liquefied; broth clouded and on the second day showing heavy yellow precipitate; milk coagulated at end of two weeks ^ Morse, W. J., Studies upon the black-leg disease of the potato, with special ref- erence to the causal organisms. Jour. Agr. Res. 8: 122, 1917. 2 Paine, Sydney G. and Chaudhuri, H., The black-leg disease of the potato. On the relationship of Bacillus atrosepticus and Bacillus solanisaprus. Phytop. 13: 359, 1923. 42 PLANT DISEASE FUNGI with extrusion of whey; agar colonies round, entire, surface smooth, sHghtly raised. No gas in dextrose, saccharose, lactose, maltose, or glycerines. Indol production moderate; nitrates re- duced to nitrites. T. D. P. 10 min., 60°; Opt. 20-30°. B. carotovorus L. R. Jones = Erwina carotovora (Jones) Com- mittee. From agar 1-2 days old as short or long rods, in short or long chains. 0.6-0.9 x 1.5-5 /x, commonly 0.8 x 2 /z; ends rounded. No spore; flagella 2-5, peritrichiate; no capsule. Gram negative; Fig. 30. — Plate culture of B. avense, on nutrient glucose agar four days at 30° C. After Manns. white on all media; agar slope filiform to spreading, glistening, opaque to opalescent. Gelatine liquefaction crateriform to infund- ibuliform. Broth clouded, pellicle thin to absent, sediment floccu- lent; milk coagulated. Agar colonies, round, smooth, entire to undulate, amorphous or granular. Some gas in dextrose, lactose and saccharose, nitrates reduced to nitrites; indol feeble. T. D. P. 51°. Opt. 25-30°. A considerable number of cultivated plants undergo soft rot of the parenchyma from the attacks of a non-chromogenic liquefying bacillus. Among the plants so affected are cabbage, turnips and other crucifers; parsnip, carrot, mangel, sugar-beet, potato, eel- PLANT DISEASE FUNGI 43 ery, tomato, Jerusalem artichoke, asparagus, rhubarb, onion, iris, calla and Coiocasia. In 1901, Jones re- ported an organism isolated from rotting carrots which he named B. carotovorus. It disorganized tissue by solution of the middle lamellae, and infection into wounds led to decay of the roots of carrot, pars- nip, turnip, radish, salsify, of onion bulbs, hyacinth corms, cab- bage heads, celery stalks and fruits of tomato, pepper and egg plant, also rot of lettuce, cauliflower, cucumber, musk- melon, potato, hya- cinth and onion. In- fection did not occur unless the epidermis was broken. The rot- ten mass was always soft, wet, and exuded a liquid clouded with bacteria. Jones in 1909 made an extensive study of the cytolitic enzyme of this germ. This enzyme was separated by heat, filtration, formalin, phenol, thymol, chloroform, diffusion, alco- hol, and its conditions of production and action in- vestigated. Heating the enzyme to 60° inhibited its activity to a marked de- gree; higher than 63° inhib- ited it entirelv; chloroform, Fig. 32.— B. carotovorus. After Jones. thymol and phcnol did not Fig. 31. — -B. carotovorus wedging apart cells of the carrot. After Smith. 44 PLANT DISEASE FUNGI retard its action. No loss was suffered through alcohoHc precip- itation and resolution. The dried enzyme remained active for fully two years. Its effect was greatest at 42°, less at 32° and 48°. No diastatic action was observable. In 1909 Harding and Morse, from an extended study of some 12,000 cultures of non-chromogenic, liquefying soft-rot bacilli of some forty-three pathogenic strains (including B. carotovorus, B. oleraceae, B. omnivorus, B. aroidese and what Potter regarded as Pseudomonas destructans), from six different vegetables, con- clude that unless later studies of the pathogenicity of these cul- tures shall offer a basis for subdividing them, there is no apparent reason why they should not all be considered as somewhat variant members of a single botanical species. This conception would lead to the abandonment of the supposed species mentioned above and the recognition of all of them under their oldest described form, B. carotovorus Jones, which in our present knowledge seems certainly to be the most wide spread, common and destructive of the soft rot bacteria. Some, perhaps much, of the rot of crucifers generally thought to be due to Pseudo- monas campestris is probably caused by B. carotovorus. B. coli (Esch.) Mig. or an organism indistinguishable from it was held by Johnston capable of causing rot of soft tissues of the cocoanut plant and to be responsible for cocoanut bud-rot. B. lathyri Manns & Taubenhaus.^ = Erwinia lathyri (M. & T.) Committee. This organism is reported on sweet peas causing ''streak." Brown spots appear on the stems and kill the cambium. Similar effects are produced on clover, bean and soy beans. B. melonis Giddings which causes a rapid soft rot of muskmelons is very close to, perhaps identical with, B. carotovorus. B. morulans Boncquet,'- an organism with four long peritrichiate flagella, is found associated with beet curly-top but a causal rela- tion to the disease has not been proved. B. musae Rorer.^ The vessels are filled with bacteria and a wilt of the plant is caused. Pathogenicity was proved by inoculation with pure cul- tures. The organism is recognized by the fact that it quickly be- comes black on potatoes. ^ Manns, T. F. A bacterial disease of the sweet pea and clovers. Phytop. 3: 74, 1913. 2 Boncquet, P. A. Bacillus morulans n. sp. Phytop. 7: 269, 1917. ^ Rorer, J. B. A bacterial disease of bananas and plantains. Phytop. 1: 45, 1911. PLANT DISEASE FUNGI 45 B. phytophthorus Appel ^ Erwinia phytophthora (App.) Committee. A non-sporiferous rod, 0.6-0.8 x 1.5-2.5 fi, actively motile by peritrichiate flagella. Gram negative; 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 precip- itated. Opt. 28-30°. T. D. P. 47°. It was described by Appel as the chief cause of potato black-leg. (See also p. 41.) The description given above, made from AppeFs organism, is by E. F. Smith, who says this organism is not suffi- ciently distinguished from B. carotovorus. The parenchyma is chiefly affected, though the vessels are exceptionally occupied, by a soft rot both in the stem and tuber. Infection is chiefly inter- cellular. B. solanisaprus Harr. A bacillus with rounded ends, 1.5-4 x 0.6-0.9 /x, variable in cul- ture; actively motile by 5-15 -f peritrichiate flagella; no spores seen. Gram negative. Gelatine colonies, punctiform 0.25 mm. at two days; gelatine stab filiform. Liquefaction noticeable on the thirty-fifth day. Agar colonies punctiform at two days, 1-5 mm., gray-white, slimy, flat. Bouillon tur- bid with fine sediment; ring, and thin band pres- ent; milk curdled . Gas only in mannite and lac- tose. 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 Har- rison regarded as distinct from black-leg and from the disease caused by Ps. 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 Fig. 33. — Surface colonies of B. solanisaprus. After Harrison. 46 PLANT DISEASE FUXGI the surrounding tissue, dissolving the middle lamellge and pro- ducing cavities. Inoculations of pure cultures into healthy plants 43 m '55 2 3 3 a -i-3 T5 0) -3 w o a a "53 a 00 2 produced characteristic lesions and the organism was re-isolated. Characteristic enzymic action was observed on placing precipi- tated enzyme on slices of potato. PLANT DISEASE FUNGI 47 B. tracheiphilus E. F. Sm. = Erwinia tracheiphila (E. F, Sm.) Committee. Bacillus 1.2-2.5 x 0.5-0.7 [x, variable, actively motile in young cultures; capsulated, no spores, flagella 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 is found filling the vessels of cucurbits, (musk- melons and cucumbers) affected with wilt. The disease has been produced artificially by puncture inoculations on the blades of leaves with the white sticky fluid from infected veins. The inoc- ulated 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 organ- ism was then isolated from this artificially infected plant. The cultures thus obtained were carried by transfers over winter and w^ >" ^^f* *^ ^T*', in December were used ♦ * >% ^'^"^^ a^^j> ''^^ ' *» ^ successfully to infect cu- **''^ ' -• •' V,l" V -/ ^< ^ I '"^'^ cumber plants. Control ^ *-* 1 , T 1 Fig. 35. — B. tracheiphilus. After Smith. plants were never diseased. The disease is transmitted by insects and gains entrance to its host through wounds. Others have been reported on corn, ginseng, beet, onion, sugar- cane, cherry, grape, hemp, lupine, calla, larkspur, dahlia, hyacinth, iris, orchids, rose, willow, poplar. 48 PLANT DISEASE FUNGI ACTINOMYCETALES (p. 14) Actinomycetacae Actinomyces Harz.^ Organism growing in form of a much-branched mycelium which may break up into segments that function as conidia. Non-motile. Actinomyces scabies (Thaxt.) Giissow = Oospora scabies Thaxt. Gelatine liquifaction slow; growth on all media gray to buff with a dark gray aerial mycelium which consists of long prostrate filaments on which lateral l^ranches are inserted at short intervals. Secondary branching abundant. Spores more or less cylindrical, 0.8-0.9 X 1.3-1.5 /ji, from dextrorse spiral hyphaj of 3-14 turns are developed richly on most media. On synthetic agar the growth Fig. 36. — Surface view of cork cells showing Fio. 37. — Section of phellogen showing fat the mycelium within. After Lutman. globules. After Lutman. is abundant, cream -colored, chiefly on surface of medium, wrinkled, raised. The aerial mycelium is white, scarce, in some strains absent. On nutrient agar the growth consists of round, entire, colonies, surface at first smooth, later raised, lichnoid, often becoming wrinkled; color white to straw, opalescent to opaque. Aerial mycelium usually absent. On potato plugs the growth is gray, opalescent, later turning jet black, wrinkled colonies covering all the plug, which also turns black. It produces scab on potato and beet. ^ Waksman, S. A. Cultural studies of species of Actinomyces. Soil Science 8: 71, 1919. PLANT DISEASE FUNGI 49 The scab on the potato may originate at any place on the tul)er, but frequently occurs at the lenticels. It is due to hypertrophy of the cells of the cork cambium, accompanied by hyperplasia. The walls of the hypertrophied cells are much thickened by suber- FiG. 38. — Drawing of a section of an old scab. After Lutman. ization. The filaments of the fungus are formed in the cork cam- bium ; and in the outer layers of the starch parenchyma fat instead of starch is present. 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. DIVISION III EUMYCETES. TRUE FUNGI (p. 2) In general the true fungi are readily distinguished from the sh'me molds and bacteria by the presence of the mycelium; excep- tions occur in the Chytridiales (p. 57) and the genus Actinomyces (p. 48). The Vegetative Body is devoid of chlorophyll and is often hyaline though sometimes colored. Typically it 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 sep- tate mycelium do not differ essentially from typical plant cells ex- cept in the absence of chlorophyll. They consist of masses of protoplasm, the proto- plasts, bearing vac- uoles and are more or less rich in oils, acids, gums, alkaloids, sugars, resins, color- ing matter, etc., vary- ing in amount and kind with the particular species and condition of the fungus. The protoplast is covered by a cell wall which con- sists 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, and dimensions, are in some cases quite characteristic. In one class, the Phycomycetes, the active vegetative mycelium 50 Fig. 39. — Showing a septate mycelium within host cells. After Stevens and Hall. PLANT DISEASE FUNGI 51 possesses no septa except such as serve to cut off the sexual or other reproductive organs or such as are found in senility. The 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 mycehum and the vegetative body consists merely of a globular, irregularly spherical or amoeboid cell. Reproduction. Vegetative. Small sections of mycelium if placed in suitable environment; that is, if supplied with food, moisture and warmth will continue to grow, soon equaling the parent mycelium in size. Bits of diseased tissue, bearing mycelium, thus constitute ready means of multiplication and dispersal. 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. Mani- fold forms of asexual spores exist among the fungi. In some of the simplest cases, b\idlike out-growths (gemmae) appear on the mycelium; 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, chlamydospores. In other cases spe- cial branches, hyphae, are set apart for the pur- pose of bearing spores. If the spores are cut off from the tip of the branch they are known as conidia or conidiospores, and the branch bearing them is a conidiophore. Conidia may be borne singly or in false clusters caused by the young pushing the older conidia aside; frequently they fig. 40.— One form are produced in chains, catenulate, Fig. 40, owing iw^Aft^/BioiSti. 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, 52 PLANT DISEASE FUNGI superficial hyphse, or they may be short, innate, and in close clus- ters forming distinct spore bearing spots. Figs. 335, 337. Such sporiferous spots when naked are called acervuli. Often the conid- iophores are roofed over with a net-work of woven fungous threads thus constituting a special spore bearing structure, the pycnidium. Fig. 41. Conidiophores '^ may be solitary or grow ^ together in bundles, Figs. 390, 391, or branch loosely as in I^ig. 351. The basidium, Fig. 42, is a special kind of sporo- phore bearing at its apex usually four, sometimes two, small projections, sterigmata, each of which produces one spore, for distinction called a basidiospore. Some fungi bear the spores loose inside of the swollen tips of sporo- phores as in Fig. 74. The spore bearing struc- ture 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 number, 1, 2, 4, 8, 16, etc., eight being the most com- mon number. Asci may be naked or covered, scattered or col- lected in groups. When covered, the chamber in which they are borne is called a perithecium, Fig. 43 ; when on an open disk the disk is called an apothecium, Fig. 109. 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 abundance in warm weather, germinate immediately, and can ordinarily live but a short time. In some species the spores that are to function in water possess FiQ. 41. -Conidia borne in a pycnidium. tance and Siiear. After Quain- PLANT DISEASE FUNGI 53 cilia, and the power of motion. These are zoospores or swarm spores, Fig. 54. 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 paren- chyma. Such are the stalks and caps of the mushrooms and of the shelving toadstools, the skin of the puffball, 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 fun- gous threads. Sexual Spores are formed by the union of sexual elements, gametes. They are most conspicuous among the Oomycetes where the antheridium Fig. 42. — Basidia of various ages. After Schenck. oscospore germinofm Fig. 43. — A perithecium with asci. After Reddick. carries the sperms into the oogonium, fertilizes the oosphere and produces an oospore. Fig. 61. As a rule the sexual spores are produced toward the end of the 54 PLANT DISEASE FUXGI vegetative period of the fungus. The asexual spores are produced earher 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 similar to that of the parent. The 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, develop. Fig. 237. 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 or- ganisms cannot develop without heat and moisture. The neces- sary degree of each varies with different species. In general the fungi that cause plant disease grow best at ordinary temperature conditions and therefore are cultured better at room temperature than at animal body temperature so often requisite for parasites of animals. Some species are strictly aquatic, and must be sur- rounded with water; others can grow in comparatively dry situa- tions. Generally speaking, however, dampness favors fungous development, and the growth of most fungi is more vigorous in damp atmosphere. Humidity and warmth combined are prover- bial 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 con- dition of fungous development. Respiration with the fungi as with all plants and animals con- sists in oxidation, involving intake and consumption of oxygen ac- companied by the giving off of carbon dioxide and water, and since no photosynthesis occurs, this process is never masked as it is in the case of the chlorophyll-bearing plants. In nutrition requirement 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 car- bon 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 on media poor in nitrogen, in which case the fungi often outgrow the bacteria. PLANT DISEASE FUNGI 55 The color of the fungi is determined to some extent by the con- stitution of the media upon which they grow, but certain colors are also characteristic of certain groups, some are typically hya- line, others brown, others red, green, etc. 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 passes 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. The mycelium is the vegetative part of the fungus and grows over or within the host tissues drawing its nourishment from the host cells and thereby rendering them diseased. Bits of tissue attacked by fungi, if teased apart, usually reveal under the micro- scope an abundance of mycelial threads. If these be constantly present, of one kind only, and no other parasites are present the presumption is that this mycelium is the cause of the disease. Certain fungi (parasites) grow only in living hosts, others (sap- rophytes) in dead organic matter. Some mycelia merely grow between or within the host cells abstracting nutriment and water from the live cells. Some produce hypertrophy or hyperplasie resulting in large distortion. Others produce toxic substances which kill single cells or tissues. Still others produce enzymes that dissolve either the middle lamellae or the cellulose walls and the affected part becomes soft and rotten. Classification of Fungi. The true fungi in themselves consti- tute a very large group made up of diverse forms, many of which are as yet little known. Any satisfactory system of classification is impossible until much more knowledge obtains regarding their morphology, cytolog}^, life histories and especially the relation to their hosts. According to present knowledge they comprise very numerous species distributed in three classes as follows: Key to Classes of Eumycetes Mycelium continuous in vegetative stage Class 1. Phycomycetes, p. 56. Mycelium septate Spores in asci Class 2. Ascomycetes, p. 87. 56 PLANT DISEASE FUNGI Spores on basidia * Class 3. Basidiomycetes, p. 210. Not as above; spores on conidio- phores, naked, or in pycnidia; or spores quite unknown Fungi Imperfecti, p. 331. Class I. Phycomycetes, Alga-like Fungi (p. 55) The Phycomycetes are characterized by the absence of septa in th myxelium 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 sex- ual spores is called the oogonium, its eggs before fertilization oospheres, and the spores oospores. The receptacle bearing the fertilizing gamete is the antheridium, and the fertilizing elements are the sperms. In some forms which, by their sexual or asexual spores, show relation to the Phycomycetes the mycelium is want- ing and the vegetative body is reduced to a single spherical or amoeboid cell, which frequently 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- nious Subclass I. Oomycetes, p. 57. Mycelium poorly developed, frequently reduced to a single cell. Fruiting my- celium 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. Chytfidiales, p. 57. Mycelium well developed 2. Peronosporales, p. 62. Sexual spores isogamous, formed by the union of similar gametes Subclass II. Zygomycetes, p. 83. Asexual spores several, in sporangia 3. Mucorales, p. 84. * In the rusts and smuts the promyceliuiii is regarded as a basidium. PLANT DISEASE FUNGI 57 Subclass Oomycetes (p. 56) 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. 56) 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 haustorium- like mycelium, while but few have any approach to a true mycelial 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- walled resting spores are produced. The zoospores have either one or two cilia. There are over forty genera and two hundred species. The majority of the species are inconspicuous parasites of algae and infusoria; but some genera, like Synchytrium, Physoderma and Urophlyctis, produce conspicuous sori and large hypertrophy of land plants. Examination of dead material of any of the Chytridiales usually discloses but little; for purposes of classification, the life history, mode of formation of sporangia and zoospores, must be ascertained. Key to Families of Chytridiales Spores all asexual, or rarely formed by the union of free-swimming gametes Mycelium none, sporangia grouped into sori 1. Synchytriaceae, p. 58. Mycelium present, of delicate, extended, evanescent, haustoria-like strands; spo- rangia terminal or intercalary 2. Cladochytriaceae, p. 60. Spores both sexual and asexual, gametes heterogamous 3. Oochytriaceae, p. 61. ^ Liidi, R. Beitrage zur Kenntniss der Chytridiaceen. Hedw. 40: 1, 1901. ^ Rytz, W. Beitrage zur Kenntniss der Gattung Synchytrium. Cent. Bact. II, 18: 635, 1907. 58 PLANT DISEASE FUNGI Synchytriaceae ^ (p. 51) The infecting zoospore invades the host cell and becomes par- asitic 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 Synchytrium the one nucleus then enlarges and divides to produce numerous nuclei. The whole mass then divides into segments re- garded 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; the protoplast becomes spherical, invests itself with a thick wall and becomes a resting spore. (Fig. 44.) After a more or less protracted period of rest zoospores develop. The family includes some fifty species, all of which, except those of two small genera, are parasitic upon land plants. Synchytrium de Bary & Woronin Zoosporangia formed by division of an initial cell to forni a sorus of sporangial cells; sporangia formed directly from the full-grown plant body. Upon reaching maturity the plant body develops directly into a sporangial sorus. Both zoosporangia and winter spores are present. S. endobioticum (Schilb.) Perc.,^ the cause of a very serious wart disease of the potato, was originally described as Chrysophlyctis endobioticum by Schiliberzky in Hungary in 1896, and trans- ferred to Synchytrium by Percival. It invaded America about 1909. In summer the resting sporangia, which average about 52 ii in diameter, 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 sporangium contains several hundred roundish zoospores which measure 2-2.5 m- In spring the resting sporangia germinate, freeing numerous, pear-shaped, uniciliate zoospores. Another type of sporangium consists of thin sacs, pro- 1 Tobler-Wolf, G. Die Synchytrien. Archiv. f. Protistenkunde. 28: 14, 1913. 2 Curtis, K. M. The life-history and cytology of Synchytrium endobioticum (Schilb.) Perc, the cause of wart disease in potato. Phil. Trans. Roy. Soc. London. 210: 409, 1921. PLANT DISEASE FUNGI 59 duced singly or two to five in a sorus, each bearing numerous zoospores or gametes. The zoospores infect the potato 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. General division of cells, neighbors to the infected cell, occurs, result- ing in a tumor. The epider- [^ mal cells surrounding the in- fected cells grow up to form rosettes overarching the host cells at their bases. By divi- sion of an infected epidermal host cell the diseased cell may l. become deeply placed in the tumor. The zoospore after Fig. 44.-A. section showing sporangia or sporo- entering the host cell enlarges 7f}^' ^' .zoospores, ciliated and amoeboid. ^ ® After Percival. and after repeated nuclear mitoses, segments to form about five thin-walled sporangia, which constitute the sorus; after more mitoses zoospores, sometimes gametes, are formed. Eventually the host cell dies and its con- 9 B Fig. 45. — S. endobioticum. Division of an epider- mal host ceil with parasites in its lower part. After Curtis. Fig. 46.— Gall of S. vac- cinii. After Shear. tents are deposited as a brown epispore upon the parasite. The zoospores at maturity are liberated by rupture of the soral envelope. Crushed sporangia produce characteristic warts in three to four days when placed on susceptible parts. 60 PLANT DISEASE FUNGI 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. Cladochytriaceae ( p. 57) 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. Physoderma Wallr. P. zeae-maydis Shaw Thick-walled, smooth, brown, resting spores, sporangia, 18-24 x 20-30 /z, each with one side slightly flattened and showing the defi- nite outline of a cap or lid, are found in great numbers within the diseased tissues. The mycelium, consisting of very fine (1/x) fibers (Fig. 47), connects the large vegetative cells which occur \ singly or in groups, and is no longer ap- f^ao.«3-__,. 5*' ■ft:.- I ■^eeBB^i^sacp^fc;. „ Fig. 47. — P. zeae-maydis. A host cell showing parasite within. After Tisdale. (^ a> ;5tri;:pg}.\ FiQ. 48. — P. zesB-maydis. Sporangium show- ing mode of opening; emerging zoospores. After Tisdale. parent when the spores are mature. In germination the lid of the resting spore opens, door-like, (Fig. 48) and soon the unicili- ate zoospores, 20-50 in number, emerge. The zoospores soon lose their cilia, become amoeboid and ger- minate by sending out very fine hyphae which penetrate into the epidermal cells. Penetration continues, the fine mycelium invad- ing a number of surrounding parenchyma cells and within produc- ing groups of enlarged cells. Some of these enlarged cells develop PLANT DISEASE FUNGI 61 directly into sporangia and the mycelium disappears. Affected cells then die. Thus large dead spots are produced on the leaves, sheaths, and stalks. On corn. Teosinte is also susceptible. This fungus was discovered in India by Shaw in 1910 and in Ilhnois by Barrett in 1911. Oochytriaceae (p. 57) 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. Only one genus is of economic importance. 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. U. alfalfse ( Lagerh.) P. Mag.i On Alfalfa causing galls. Infection is by zoospores and turbinated bodies are produced within the epidermal cells and attached by a beak. Fig. 49. This Fig. 49 . — U. Alfalfse. Section of epidermis showing primary turbinated cells, ta, tb, etc., each with several nuclei. After Jones and Drechsler. body, at first uninucleate, becomes multinucleate and by septation and branching brings about a structure such as is shown in Fig. 50, new series of turbinated cells being formed on the ends of delicate ^ Jones, F. R. and Drechsler, C. Crown wart of alfalfa caused by Urophlyctis alfalfse. Jour. Agr. Res. 20: 295, 1920. 62 PLANT DISEASE FUNGI (0.5-1 m) mycelial filaments and resting spores forming on the turbinated cells. The resting spores are the most conspicuous structures found on dissection of diseased tissue and are yellow, brittle, about 40 fj, in diameter and with a thick (1.5 ijl) wall. The haustoria disappear on old resting spores. The fungus primarily attacks the very young leaf scales and leaves of the bud. The in- vaded cells and the adjacent cells undergo hypertrophy, producing galls. The walls of the host cells are dissolved before the advance of the fungus producing large cavities. Other species are on beets, Chenopodium, Atriplex and clover. Peronosporales (p. 56) The mycelial threads in most strictly parasitic forms wander be- tween the host cells and draw nutriment from them by short branches, sucking organs, haus- toria, (Fig. 60) of various forms, which penetrate into the victimized cell. Two kinds of spores are pro- duced, sexual and asexual. The sexual spores result from the union of two unlike gametes, the egg (oosphere) and sperm, borne '''S;eS-7f^u'"a"a£'1a;''tb*tuSS respectively in the oogonium cells, ra, resting spore. Haustona are and autheridium. Each OOgOnium seen on the tips oi the turbinated cells and encircling the resting spore. After bcarS a Solitary OOSphcrC. FcrtlllZa- Jones and Drechsler. ... t i i i /• tion IS accomplished by means ot a tube from the antheridium and penetrating into the oogonium. The sexual spores are thick-walled, resistant, and usually require a long time to reach maturity. They are, therefore, often called ''resting spores. " In germinating the sexual spores produce either germ tubes or develop directly into zoosporangia. The asexual spores are conidia. They are borne on conidiophores which arise from the mycelium and which may be short or long, simple or branched, subepidermal or superficial according 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 en- PLANT DISEASE FUNGI 63 tire protoplasmic contents of tiie spore passes ouside the spore wall and then forms a germ tube, or (3) the conidium by internal di- vision breaks up into zoospores. Key to Families of Peronosporales Conidiophores poorly defined or of sympodial development . . : 1. Pythiaceae p. 63. Conidiophores not as above Conidiophores, short, thick, subepidermal, conidia catenulate 2. Albuginaceae, p. 70. . Conidiophores, longer, superficial, simple or branched, conidia not catenulate 3. Peronosporaceae, p. 73. Pythiaceae ^ This family shows affinity with both the Peronosporales and the Saprolegniales and is sometimes classed with one, sometimes with the other. Zoospores differentiated outside of the zoospo- rangia 1. Pythium, p. 63. Zoospores usually differentiated within the zoo- sporangia Fertile mycelium delicate 2. Pythiacystis, p. 65. Fertile mycelium robust 3. Phytophthora, p. 66. Pythium Pringsheim ^ (p. 63) The mycelium is found in abundance in and about the infected tissue as fine, branched, continuous threads. These, in the terres- trial species, bear conidia on branches which are of the same char- acter as the mycelium 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 appearance, are also produced. The oogonia are quite like the conidia and gemmae in structure, but develop oospores within. The oogonium is at first multinu- cleate but as the oosphere matures all of the nuclei except one mi- grate toward the periphery, the periplasm, or degenerate in the ^ Fitzpatrick, H. M. Generic concepts in the Pythiaceae and Blastocladiacese. Mycol. 15: 166, 1923. - Butler, E. J. An account of the genus Pythium and some Chytridiaceae. Mem. Dept. Agri., in India, Botanical series 1, no. 5; 1, 1907. 64 PLANT DISEASE FUNGI ooplasm, resulting at maturity in an uninucleate egg. This is fertilized by one nucleus from the antheridium. No sperm is differ- FiG. 51. — Cucumber seedlings. Pots 5, 0, and 8 inoculated with Pythium. Pot 7, Control. After Atkinson. entiated, and the contents of the antheridium are carried over to the egg by a fertilizing tube. Members of the genus are aggres- sively parasitic only under most favor- able environmental conditions of heat and moisture. P. debaryanum Hesse ^ is most com- mon as the cause of ''damping off." Zoosporangia or "conidia" globose to elliptic, usually papillate, 20-25 ji; gemmae similar in form and size; oospores globose, hyaline, smooth, 15-18 /x. It is also recorded as the cause of Fio. 52. — Fertilization in Pythium, ,/, ijj • ^ p, , p iv. t*i showing oogonium, antheridium, leak, a rapid SOlt rot, 01 the ll'ish oospore, periplasm and the cT nntatn and 9 nuclei. After Miyaki. putctuu. Studies have shown that P. debar- yanum destroys pentosans, starch and sugar in potato tubers. It secretes a toxin which kills the cells, also an enzyme that dissolves ^ Hawkins, L. A. and Harvey, R. B. Physiological study of the parasitism of Pythium debaryanum. Hesse on the potato tuber. Jour. Agr. Res. 18: 275, 1919. PLANT DISEASE FUNGI 65 the middle lamella. It is claimed that the cell walls are penetrated by mechanical pressure. Fig. 53. P. aphanidermatum (Edson) Fitzpatrick Mycelium 2.8-7 n; presporangia terminal, clavate or branched, 50-1000 X 4-20 /JL, sporangia becoming spherical on release, then cleaving into zoospores which are plano-convex and biciliate, 12 x Fig. 53. — Drawings showing mode of penetration of potato-cell walls by Pythium: I Swelling of the hypha on contact, followed by penetration by a small tube. VII showing bending of wall by hyphal pressure. After Hawkins and Harvey. 7.5 fjL; oogonia terminal, spherical, 22-27 fx; oospores single, 17 x 19 /JL. The cause of ''damping off" in beets and of black-root of radish. Other species occur on ferns, ginger and palm. Pythiacystis, Smith & Smith (p. 63) 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, and this of close kinship with Phytophthora. P. citrophthora 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 Ai, averaging 35 x 50 pt, borne sym- podially; zoospores 10-16 /jl, at first elon- gate, becoming rounded and bearing two lateral cilia. Infection by pure cultures prove that Fig. 54.— p. citrophthora; de- ,1 /. • ji J f ii , velopment of swarmapores the lUngUS is the true cause 01 the rot. from sporangia. After Smith r~\ • • I'lj^i 1111 and Smith. Gummosis, m which the dead bark re- mains hard, is also caused on lemon twigs by this fungus. 66 PLANT DISEASE FUNGI Phytophthora de Bary ^' -• (p. 63) 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 parasitic fungi to receive study in any way complete or adequate; study more- over which did much to turn at- tention and interest toward plant pathology. In most species the conidiophores „ ,. cj • I , have irregular thickenings below the b IG. 55. — hporangiophores and sporangia ^ ^ . . of Pythiacystis. After Smith and apparently lateral couidia. The conidiophore 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 scorpioid cyme is pro- duced. The mycelium is much branched, non-septate, hyaline; the conidiophores arise singly or in groups from the stomata, or break through the epi- dermis; conidia oval, papillate; zoospores oval, biciliate, escaping by rupture of the papilla; oospores, when present, with the epispore more or less ridged. The mycelium characteristically lives in and between the dead cells, not in the live cells of the host. P. phaseoli Thaxt. 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- Fio. so.-structurai details 24 fx; 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 m; oospores spherical or subspherical with smooth, mod- erately thick walls, hyaline or light yellow, 18-26 fx. It was de- 1 Wilson, G. W. A review of the genus Phytophthora. Mycol. 6: 54, 1914. 2 Rosenbaum, J. Studies of the genus Phytophthora. Jour. Agr. Res. 8: 233, 1917, of P. phaseoli. Thaxter. After PLANT DISEASE FUNGI 67 scribed 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 artificial culture experiments made, by Clinton who first grew the fungus successfully in pure culture on corn-meal agar and other media. 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 Mycelium well developed; conidiophores single or in groups of 2-4 from the stomata; scorpiose-cymosely branched ; conidia 27-30 x 15-20 fx, ovoid, germinating by about six to zoospores. On solanaceous hosts, particularly the potato and tomato, this species is very destructive. It was first described in 1845 as a Bo- trytis and has since been the subject of many extensive papers. The conidiophores are abundant on the lower sides of infected leaves near the invasion line. The mycelium migrates between the cells piercing them with haustoria. The existence of oospores was a much controverted point; the structures first reported as oospores probably belonged to some other fungus. Within recent years Clinton has obtained in pure cultures perfect oogonia, antheridia and oospores. In germination the conidia give rise to oval, flattened, biciliate zoospores which emerge, come to rest, develop a wall, and then produce a germ tube. Direct germination by a germ tube also occurs rarely. Infection is brought about by the germ tube, either penetrating through stomata or directly through the epidermis. The walls and contents of parasitized cells are browned. This fungus alone on tubers induces dry rot, but invasion of numerous saprophytic fungi and bacteria usually turns this into a disagree- able wet rot. Tuber infection occurs largely from conidia washed sixteen F^^- 57. — Young and mature oospores of P. phaseoli. After Clinton. 68 PLANT DISEASE FUNGI into the soil by rain; possibly sometimes by the mycelium migrat- ing by way of the stem. The fungus in pure culture was extensively studied by Jones and FiQ. 58. — P. infestans; 1, section showing conidiophores and conidia formation; 5, germination of conidia. After Scribner. a decided difference in luxuriance of growth was observed on blocks cut from different varieties of potatoes. Hibernation occurs in part, at least, in live mycelium in infected tubers. The conidia are short-lived especially when dry. P. omnivora de Bary. Conidiophores simple or branched; con- idia ovoid or lemon-shaped, 50-60 or even 90 x 35-40 fx, germinat- PLANT DISEASE FUNGI 69 ing by as many as fifty zoospores; oospores smoothish or wrinkled, light-brown, transparent, 24-30 /z. This species is found upon seedlings of some fifteen families ranging from Pines to the higher Angiosperms. P. parasitica Dastur. var. rhei Godfrey.^ Mycelium at first continuous, later sparingly septate; 5-15 fj. in diameter, mostly intercellular, producing haustoria which may be small and subspherical, or finger- like; sporangiophores not distin- guishable from the mycelium; spo- rangia usually terminal, normally ovate and papillate, mostly 24-35 Fiq. 59— Formation of swarm-spores of nn Aa ' j.- r, •• Phytophthora. After Smith. X 3o-48 fjL, germmatmg by zoo- spores or rarely by germ tubes; zoospores biciliate, 8-9 x 11-13 yu, becoming globoid; chlamydospores globose, 27^2 /jl, walls thick; oogonia abundant in old cultures, 24-33 fi in diameter, pale to brownish; antheridia variable; oospores globose, thick- walled, mostly 24 fx in diameter; profuse on most vegetable culture media. Parasitic in the base of leaf petioles and roots of rhubarb caus- ing rot followed by sudden wilting of the foliage. The fungus ad- vances from the leaf base into the root causing a brown decay. Death of alt the leaves and of the plant may result. P. cactorum (Lib. & Cohn) Schr. also causes a rot of rhubarb,^ in general much like that described above though the fungus is adapted to lower temperatures and therefore is less injurious in hot weather, although there is little difference in the ultimate damage caused by the two. The fungus usually enters through wounds; the mycelium is intercellular with haustoria. This fungus occurs also on apples, pears, tulip and ginseng. P. terre stria Sherbakoff Mycelium at first continuous then septate; conidia usually terminal, mostly oval, 36-46 x 24-35 /x, germinating mostly by ^ Godfrey, George H. A Phytophthora footrot of rhubarb. Jour. Agr. Res. 23: 1, 1923. - Beach, W. S. A crown rot on rhubarb caused by Phytophthora cactorum. Pa. Agr. Exp. Sta. Bui. 174, 1922. 70 PLANT DISEASE FUNGI swarm-spores; swarm-spores asymmetric, with two cilia on one side, 9-11 M when in resting globoid stage; chlam3^dospores com- mon, mostly globose, 30-40 /x; oogonia common in old cultures on steamed bean pods, globose, 19-24 u.] oospores globose, 18-21 ji; colonies on corn-meal agar, tufted. Parasitic in tomato fruit causing buckeye rot ; in bark of trunks of citrus trees causing foot rot; in stems of Lupine causing stem rot. P. capsici Leonian ^ Sporangiophores branched; sporangia generally ovoid, varying in culture to ellipsoid, subspheroid or irregularly elongate; papilla very prominent, germination normally by zoospores, under special conditions by germ tubes; size of sporangia variable, 35-85 or even 105 x 21-56 ju; oospores formed on submerged mycelium, abundant on oat-meal and corn-meal agars, slightly wrinkled, brown, semi-transparent, 25-35 /z; antheridia basal; no chalmy- dospores observed. Parasitic on stems and fruit of pepper. Other species are on lilac, tobacco, colocasia. Agave. Albuginaceae - (p. 63) There is a single genus, Albugo (Persoon) Roussell,- of about fifteen species entirely parasitic upon flowering plants, causing the "white rusts." The conidia are borne in white blister-like sori under the raised and finally ruptured epidermis of the host. The conidiophores are short, club-shaped, arranged in clusters; the spores are borne in basipetal succession and remain attached in rather long chains unless disturbed. The mycelium is very fine, intercellular, obligate parasitic, and penetrates the cells by globular haustoria. The rudimentary oogonium is multinucleate and filled with uniform protoplasm. 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. 61, 63, 64. ^ Leonian, Leon, N. Stem and fruit blight of peppers caused by Phytophthora capsici Sp. Nov. Phytop. 12: 403, 1922. 2 Wilson, G. W. Studies in North American Peronosporales. I. The Genus Albugo. Bull. Tor. Bot. Club. 34: 61, 1907. II. Phytopthoreae and Rhysotheceae. Ibid. 34: 387, 1907. III. New or Noteworthy species (Species of Albugo and Peronospora, Ibid. 36: 361, 1908. IV. Host Index. Ibid. 35: 543, 1908. PLANT DISEASE FUNGI 71 During this process the nuclei enlarge, undergo one or two mitoses, Fig. 64, and in some species all the nuclei except one pass to the periplasm. In other species the oosphere is multinucleate at i Fig. 60. — Albugo. A, section through a sorus showing epidermis, conidia, conidio- phores and mycelium; B, conidiophores and conidia; C, mycelium and haustoria. After Bergen and Davis. maturity, Fig. 61. The latter type is fertilized by numerous nuclei from the antheridium, the former by a single nucleus. After fertilization the oosphere matures to form an oospore. The globular oospores fall into two classes; first fcuberculate or ridged; sec- ond, reticulated. These are illustrated in Fig. 62. While the conidial stages are common, oospores are less so. Conidia germi- nate freely only if they are chilled, and in germination usually produce several ovate zoospores with unequal, lateral cilia. After a brief period of motility they became walled and produce germ tubes capable of infecting susceptible fig. ei.— Multiple fertilization in hosts. The oospores after a period of i'aSSg spt?ms"' A^t^er stivet: rest germinate in a similar manner. Albugo is readily recognized from its conidial sori and the species can usuall}^ be inferred by means of a host index; though for accurate determinations oospores are needed. A. Candida (Pers.) Roussel. Sori on all parts of the host except the roots, white or rarely light yellow, prominent and rather deep- 72 PLANT DISEASE FUNGI seated, variable in size and shape, often confluent and frequently producing marked distortion of the host; conidiophores hyaline, clavate, about 35-40 x 15-17 m; conidia, globular, hyaline, with FiQ. 62. — Oospores of Albugo. 1. A. Candida. 7 A. bliti. 8. A. platensis. After Wilson. uniformly thin walls, 15-18 ix; oospores, much less common than conidia, usually confined to stems and fruits, chocolate-colored, 40-55 ix; 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 Fig. 63. — A. bliti, young oogonium and antheridium showing nuclei. After Stevens. Fig. 64. — A. bliti, show- ing differentiation of ooplasm and peri- plasm, the nuclei in mitosis. After Stevens. Fig. 65. — A. bliti, an- theridium showing the multinucleate tube. After Stevens. of cruciferous hosts, and often gives rise to very pronounced hypertrophy. Practically all cultivated crucifers, cabbage, radish, turnip, horseradish, etc., are subject to attacks of this fungus, as also are the caper, mignonette, and Tropoeolum. PLANT DISEASE FUNGI 73 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, unequally curved at base, 15 x 30 //; conidia hyaline, short-cylindric, all alike or the terminal more rounded, 14-20 x 12-18 ^u; the mem- brane with an equatorial thickening, usually very pronounced. Oosporic sori separate from the conidial, caulicolous, 1-2 x 5-6 cm. or even more, causing marked distortion; oospores light yellowish-brown, 25-55 ii; epispore papillate or with irregular curved ridges. Common throughout the world on various species of Convol- vulacese; morning glory, moon flower, sweet potato, etc., although causing but little damage. A. tragopogonis (DC.) S. F. Gray. Sori hypophyllous or caul- icolous, prominent, deep-seated, white or yellowish, pulverulent, rounded or elongate, 1-3 x 1-8 mm; conidiophores hyaline, clavate, about 12-15 X 40-50 m; conidia, 12-15 x 18-22 n; light yellow or hyaline, short-cylindric, the terminal larger and less angular than the others, membrane with an equatorial thickening; oospores produced in stems and leav^es, dark brown or almost black at maturity, opaque, 44-68 ix, epispore reticulate, areolae 2 yu; wing bearing papillate tubercles at its angles. A cosmopolitan species on the Compositse. Salsify is the chief economic host. A. occidentalis Wils. is reported on the beet; A. portulaceae (DC.) Kze. on purslane and A. bliti (Biv.) Kze. on Amaranthus, beet and related plants. Peronosporaceae ^ (p. 63) The members of this family produce the diseases commonly known as the "downy mildews." They contain many important plant pathogens. The oospores are in general indistinguishable from those of Albugo but the conidiophores are quite different, being aerial instead of subepidermal. In most cases they are branching and tree-like, Fig. 69, but in a few genera they are short. The oospore in Peronospora and Sclerospora is formed as in Albugo resulting when mature in an uninucleate egg surrounded by a ^Farlow, W. G. Enumeration of the Peronosporaceae of the U. S. Bot. Gaz. 8; 305, 1883. 74 PLANT DISEASE FUNGI periplasm bearing the degenerate supernumerary nuclei. Fer- tilization is as in the Albugos that have an uninucleate egg. The family has suffered many revisions of classification and much renaming of genera. Plasmopara and Peronospora are especially rich in a masquerade of names. In practice Sclerospora is readily recog- nized by its oospores ; Bremia by the peculiar formation of the apices of the conidiophores (Fig. 71). The remaining genera Nos. 2, 3, 5 are closely related and difficult of differ- entiation. In addition to the key charac- ters, the general habit of the conidiophores as shown in Figs. 69, 72 aids in distinguishing Plasmopara from Peronospora, while Pseudoperonospora is intermediate between these two in mode of branching. Fig. 66. — Haustoria of a Per- onospora. After Zopf. 1. Sclerospora, p. 75. Key to Genera of Peronosporaceae Conidiophores regularly monopodially branched; with the main axis not in- durate, conidia germinating by zoo- spores or by a plasma Conidiophores fugacious, stout, spar- ingly branched; oospore perma- nently united to the wall of the oogonium Conidiophores persistent, slender, usu- ally freely branched; oospore free from the wall of the oogonium Branches of the conidiophore apically obtuse 2. Branches of the conidiophore apically acute 3. Conidiophores dichotomously branched; conidia germinating by a germ tube. Conidiophores with subapical disk-like enlargements from which the ul- timate branchlets arise radially; germ tube produced from the apex of the conidia 4. Bremia, p. 79. Conidiophores without subapical en- largements; conidia germinating from the side 5. Peronospora, p. 80 Plasmopara, p. 76. Pseudoperonospora, p. 78. PLANT DISEASE FUNGI 75 Sclerospora Schroter (p. 74) This genus differs from all other Peronosporales in the prepon- derance of its oospores; these are the conspicuous stage, while the conidiophores and conidia are few, small and evanescent. An exception to this statement apparently occurs in S. philip- pinensis. MyceHum much branched, with small vesicular haustoria; co- nidiophores erect, solitary or in groups of two or three, fugaceous, low and stocky, sparsely branched, the branches also stocky; co- nidia elliptic or globose-elliptic, hyaline, smooth; oospores globose, intramycelial, the epispore brown, irregularly wrinkled, perma- nently united to the persistent wall of oogonium. S. graminicola (Sacc.) Schr. infects leaves and inflorescences, the oospores causing marked distortion of the latter and rapid Fig. 67. — S. graminicola. Conidiophores and co- nidia; germinating co- nidia and zoospores. After Butler. Fig. 68. — S. graminicola, oogon- ium, oospore and antheridium in section. After Stevens. disintegration of the former; conidiophores 100 x 10-12 ix, conidia 20 X 15-18 ^) oogonium wall thick, 4-12 ji, at maturity 30-60 /i in diameter, reddish-brown; oospore pale brown, 26-36 ^t. 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. On millet (Setaria italica), pearl millet, fox tail and corn. S. macrospora Sacc. has been reported in corn tassels and on wheat. Conidia unknown; oogonia embedded firmly in the tissue 76 PLANT DISEASE FUNGI of the host, not causing disintegration as in S. graminicola; oospores light yellow, smooth, 60-65 /x. S. philippinensis Weston ^ causes serious disease of corn in the Philippines. Conidia common and abundant; oospores rare, not seen on corn. Conidiophores emerge from the stomata, 150-400 /x long X 15-26 yu thick, dichotomously branched 2-4 times. Conidia 27-39 X 17-21 fjL. S. spontanea Weston, a closely related species, occurs on sugar- cane, sorghum and corn. Plasmopara Schroter (p. 74) The tree-like, branching conidiophores. Fig. 69, are common to this genus, Peronospora, Pseudoperonospora and Bremia, and unlike the conidiophores of Phytophthora they are completely formed before they begin to bear spores. Mycelium branched; haustoria simple; conidiophores erect, 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., collected in 1834 by Schweinitz and regarded as a Botrytis was first published in 1851. Hypophyllous, caulicolous, or on young fruits, covering the in- fected areas with a white, downy growth; on the leaves epiphyllous discoloration yellowish; on the fruit often causing a brown rot without producing conidia; conidiophores fasciculate, 250-850 x 5-8 fx, 4-5 times branched, the ultimate branchlets about 8 ji long; conidia ovate-elliptic, very variable in size, 9-12 x 12-30 ju; oospores 30-35 m, epispore brown, wrinkled, or almost smooth; oogonium thin-walled, hyaline or light yellowish-brown. The mycelium on Vitis is found in all diseased tissues except the xylem. The conidiophores issue from stomata. The conidia germi- nate readily in water, producing in about three-fourths of an hour biciliate zoospores. These after fifteen to twenty minutes activity ^ Weston, Wm. H. Philippine downy mildew of maize. Jour. Agr. Res. 19: 97, 1920. PLANT DISEASE FUNGI 77 cease motion, round off, become walled, then germinate by a tube. This tube bores through the epidermis and develops into the inter- nal mycelium. Infection is almost exclusively from the lower side of the leaf, and through the stomata, and is followed by typical spots in about 11 days. Oospores are much more rare than co- FiG. 69. — P. viticola. A, section of a leaf with conidiophores emerging from a stoma; C, formation of swarm-spores; D, formation of oospores. After Millardet. nidia 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 per- ennate in old wood, and even form oospores therein. The fungus is dependent on abundant moisture. Other species are on umbellifers including the parsnip and carrot, currant, Helianthus, Impatiens, Aconitum and cultivated hepaticas. 78 PLANT DISEASE FUNGI Pseudoperonospora Rostew. (p. 74) There are four species which have been variously designated as Peronospora, Plasmopara, Pseudoperonospora and Peronoplas- mopara. The genus combines colored conidia and zoosporic germi- nation with a type of conidiophore intermediate between those of Peronospora and Plasmopara. Mycehum 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. cubensis (B. & C), Rostew. Hypophyllous, rarely amphigenous; discoloration of the host yellowish or water-soaked; conidiophores 1-2 rarely more from a stoma, 180-400 x 5-9 /z, 3-4, rarely 2-5 times branched, the ulti- mate branchlets recurved; apically acute, 5-20 fi long; conidia gray, brownish or smoky, ovoid to ellipsoid, papillate, 20-40 x 14-25 ix; oospores spherical, yellowish, warty-papillate, 30-43 p., maturing in the decaying leaves. The intercellular hyaline, irregular, branching mycelial threads abound in the spongy parenchyma, penetrating the cells by short, ovate haustoria. 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 flattish 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 either above or below. Moist weather is favorable to 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 infec- tion; conidia some nine or ten days after infection. When the in- vaded host cells die the conidiophores therefrom cease to function. For many years after its discovery in 1868 in Cuba this fungus was not well known even scientificall}^, its first serious outbreak being about 1889. It appeared in Japan about the same time and is now known to be almost cosmopolitan. Oospores have not been seen in America. Many wild and cultivated cucurbits are infected, among them the pumpkin, squash, cucumber, muskmelon, water- melon, and gourd. The fungus is especially prevalent on cucum- PLANT DISEASE FUNGI 79 bers raised under glass. Clinton infected muskmelons with spores produced on cucumber. P. celtidis (Waite) Wil. on hackberry and P. portoricensis Lam. Fig. 70. — P. cubensis: 3. Conidiophore with young and old co- nidia. 5. Conidium. 6. Conidium germinating. 11. Zoo- spores. 18. Infection through a stoma. After Clinton. on the chinaberry are the only species in the family that infect dicotyledonous trees. P. humuli Miy. & Taka causes hop disease. Bremia Kegel (p. 74) This genus resembles Peronospora except that just below the ends of the conidiophore branches there are pronounced swellings from which spring radially a number of short branches each bear- ing an ovate, papillate conidium. The conidia germinate by apical germ tubes. There is only one species. 80 PLANT DISEASE FUNGI Fio. 71. — B. lactucsB. After Tubeuf. B. lactucae Regel is found on lettuce and several other of the Compositse. Hypophyllous or amphigenous, causing discoloration, then wilt- ing of the host; conidiophores produced singly but in great abun- dance, much branched; conidia ovate, 16-22 x 15-20 jjl; oospores small, 26-35 /*, light brown, the epispore wrinkled. Peronospora Corda (p. 74) This genus contains several aggressive para- sites. Its conidiophores are much like those of Plasmopara but with more tendency to dichotomous branching and to more graceful habit; the apices are acute. Mycelium well developed, haustoria fili- form, simple or branched; conidiophores di- chotomously 2-10 times branched at acute angles, ultimate branchlets acute, more or less reflexed; conidia hyaline or colored, pa- pillate, germinating directly by lateral germ tubes; oospores globose, reticulate, tuber- culate, wrinkled or smooth. P. parasitica (Pers.) de Bary. This is often associated with Albugo Candida, giving it the appearance of a parasite on that fun- gus. Almost all species of Cruciferse are subject to attack, among them cabbage, cauliflower, radish, collards, turnips, horse- radish, and others of minor economic impor- tance. It is cosmopolitan in distribution. The fungus covers any green part of the host with a dense, white growth, often caus- ing hypertrophy, especially in oospore forma- tion; conidiophores 200-300 x 10-12 fx, bushy branched, stout, deliquescent, with 5-8 main branches, each from 3-7 times branched, Fio. 72— p. effusa on spin , . . , , , , ,1 , ach. After Halsted. ultimate branchlets slender, more or less curved, usually arising at acute angles, about 12-15 x 2-3 ijl; conidia broadly elliptic, blunt, often becoming globose, about 12- 22 X 24-27 IJL, hyaline or very light ; oospore globose, yellow-brown, 26-45 ji, epispore smooth or wrinkled; oogonium thick, colorless. PLANT DISEASE FUNGI 81 P. efifusa (Grev.) Rab. causes a serious disease of spinach. It also occurs on a wide range of weeds of the Chenopodiacese. Hypophyllous, causing yellow or brown 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 re- curved, 8-15 X 3-4 11] conidia elHpsoid to globose 17-18 x 22-24 ^, violet or smoky; oospores globose, 30-40 //, epispore light brown, more or less regularly wrinkled; oogonium thin, brown. P. schleideni Ung. was first described as a Botrytis in 1841. It was noted in America in 1872. The conidia in mass present a purplish tint. The conidio- phores usually emerge singly through the stomata. The mycelium is intercellular and from it slender, branched haustoria are given off to the parasitized cells, their ends often wrapped around the nuclei. In water the conidia germinate directly to form an infec- tive tube (Fig. 73) which enters the host through the stomata. Conidia retain their germinating power only a few hours. Fer- tiUzation occurs much as in P. parasitica (Fig. 73) and the sexual spores, which abound, serve for hibernation. They may live sev- eral years. The fungus is found on onion, garlic, etc. (Allium sps.), covering leaves with a dense growth; conidiophores, 3-6 times branched, 300-700 X 12-15 /x; branches 2-5, scattered, ultimate branchlets subulate, 15-20 ix, 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 ix, epispore smooth or slightly wrinkled. P. trifoliorum de Bary. Hypophyllous, forming a dense, grayish or dirty-white growth over the host; conidiophores slender, 360- 600 X 9-11 n, 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 an- gles, straight, subulate, 7-12 x 7-3 ix) conidia globose to broadly elliptic, 15-20 x 18-36 )U, violet; oospores globose, 24-30 ju> epi- spore light brown, smooth. It causes serious loss to clover and species of related genera, particularly alfalfa. It differs from P. vicise 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 82 PLANT DISEASE FUNGI or inconspicuous; conidiophores fasciculate, 300-700 x 9-11 m, 5-8 times branched, the main branches arising at acute angles, 14 15 Fig. 73. — P. schleideni. 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. 13. Young conidiophores, (a, a) turning toward the stoma, (b); (c) haus- torium 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 antheridium, (d) still attached; (b) mature oospore still inclosed in the old wall of the oogonium. After Whetzel. erect, the ultimate subequal, slightly flexuose, arising at right or obtuse angles, the lateral recurved, 10-17 x 2-3 m; conidia elliptic. PLANT DISEASE FUNGI .83 P. hyoscyami de Bary appeared on tobacco in Florida in 1921 in apparently serious form. Other species are on Rubus, strawberry, rose, violet, pansy, Colocasia, primrose, forget-me-nots and many other plants. Zygomycetes (p. 56) This group of fungi is readily distinguished from the Oomycetes by its isogamous sexual organs, when these are present. In the Fig. 74. — A sporangium with a columella (Mucor). After Sachs. 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. The mycelium, if young, serves to indicate relationship to the Phycomycetes. Older mycelium is often septate and would lead the unwary into errors of classification. 84 PLANT DISEASE FUNGI Asexual spores are either in sporangia or are borne as conidia. The spore-bearing stalks exhibit wide diversity in shape and form of branching. Sexual spores (zygotes) are produced through the union of two like gametangia. (Fig. 75). Mucorales ^ (p. 56) This order is comprised mainly of saprophytes; 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 Fig. 75. — Mucor: zygospore formation. After Brefeld. Fig. 76. — Phycomycetes showing zygosporic lines at regions of con- tact between + and — strains. Af- ter Blakeslee. 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 are to all appearances alike, the plants are in reality dioecious; that a branch from one plant cannot produce sexual organs that will unite with other sexual organs produced upon the same plant. Moreover, there appears to be a differentiation of sex in that one plant, which may provisionally be regarded 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 1 Sumstine, D. R. The North American Mucorales. I. Mycol. 2: 125, 1910. PLANT DISEASE FUNGI 85 with the females. In some species the plants of one sex show a more luxuriant vegetative growth than do plants of the other sex. Key to Families of Mucorales Asexual spores in typical sporangia, al- though in some genera few spored ; spor- angium with columella; zygospores naked or thinly covered with outgrowths of the suspensor Mucoraceae, p. 85. Asexual sporangia of two kinds, polysporic and monosporic Choanephoraceae, p. 86. Mucoraceae Asexual spores in typical sporangia, although in some genera few-spored; sporangium with columella; zygospores naked or thinly covered with outgrowths of the suspensor. 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 by zygospores formed by the union of equal gametes; spo- rangiophores 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 va- riable, smooth or spiny, borne on short branches of the mycelium. Rhizopus Ehrenberg ^ Sporangial membrane thin and fugaceous throughout ; sporangia all similar; mycelium differentiated into a colorless vegetative and a colored aerial region. Aerial mycelium stoloniferous, zygo- spores formed in the substratum; sporangiophores arising from the nodes. The sporangium wall is not cutinized and falls away. The sporangia are all of one kind with columellas. The ^oran- giophore is never dichotomous. The suspensor is without out- growths. R. nigricans Ehr. Aerial mycelium at maturity chocolate colored; rhizoids numerous; sporangiophores fasciculate, erect, aseptate; sporangia globose, blackish-olive, granular; columella hemispheric; spores gray to brown, subglobose or irregular, 11-14 /x; zygospore 150-200 fj,, epispore with rounded warts, black. This ^ Hanzawa, J. Studien iiber einige Rhizopus-Arten. Myc. Cent. 5: 231, 1915. 86 PLANT DISEASE FUNGI Fig. 77. — Rhizopus. Diagram showing mycelium and sporangiophores. After Coulter, Barnes and Cowles. is the cause of soft rot of stored vegetables and fruits, particularly of sweet potatoes, Irish potatoes, beans, apples, pears, tomatoeS; strawberries, peaches, plums, raspberries, currants and quince. It also causes death of squash blossoms and is destructive to barley during malting. It is dis- tinctly a wound parasite and is unable to force entrance through a sound epidermis. On strawberries the my- celium passes between the cells, along the middle lamellae, and causes the protoplasm of adjacent cells to shrink. A temperature of 8°C. decidedly retards its growth, but its rate of growth increases rapidly with rise of temperature above that point. The richly branched mycelium which varies from very thin and hyahne to thick, coarse and slightly fuscous, is found throughout the rotton portion of the hosts. After a period of luxuriant vegeta- tive growth hyphse 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 bear- ing one terminal sporangium. The sporangia are at first white, later black and contain very numerous spores. Aerial stolon-like hyphae reach out in various directions and at their points of con- tact with some solid develop holdfasts (Fig. 77) and a new cluster of sporangiophores. Zygotes are produced by union of two mycelial tips as is shown in Fig. 75. Rhizopus tritici Saito,^ which causes a similar rot of sweet pota- toes, has been extensively studied regarding its production of amylase. Six other species have by inoculation experiments been shown capable of rotting sweet potatoes. Choanephoraceae (p. 85) Mycelium parasitic on living plants; sporangia of two kinds; macrosporangia globose, columella small, spiny, spores few, on ^ Harter, L. L. Amylase of Rhizopus tritici with a consideration of its secretion and action. Jour. Agr. Res. 20: 761, 1921. PLANT DISEASE FUNGI 87 simple or branched, erect sporangiophores; microsporangia clavate, one-spored simulating conidia and borne in heads on the enlarged apices of umbellately branched sporangiophores; zygospores as in Mucoracese. Choanephora cucurbitarum (B. & Rav.) Thaxt.^ is the cause of decay of cucurbits, especially pumpkins, also of okra. It also blights the blossoms. ASCOMYCETES (p. 55) The distinguishing mark of this group is the ascus. This in its typical form is shown in Fig. 78, 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, constituting 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. 78. The hymenium may be borne in or upon a 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, texture, 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 Fio. 78.— Portion of a 1 1 J -J i 1 J • 1 1 hymenium showing parenchyma and constitutes relatively large asci and paraphvses. spore-bearing structures. Fig. 79. ^^''' Chamberlain. The ascigerous organ, ascocarp, or ascoma, if saucer-shaped and open is an apothecium, Fig. 109, if closed a perithecium, Fig. 159. In other cases, the ascigerous layer covers the exterior surface. Fig. 79. On the boundary lines between the Ascomycetes and other groups are fungi which do not present the typical Ascomycete ^ Wolf, F. A. A squash disease caused by Choanephora cucurbitarum. Jour. Agr. Res. 8: 319, 1917. 88 PLANT DISEASE FUNGI picture })ut which are regarded as probably belonging to the group, i, e., transition forms between this and other groups. Among such are forms in which the asci are without either stroma or covering (Protodiscales, p. 95); others in which the asci are not even in groups but are scattered irregularly throughout the ascocarp Fig. 79. — The large ascocarp of the morel. After Freeman. (Aspergillales, p. 122); and still others with the asci neither in regular groups nor covered (Protoascomycetes, p. 92). Besides the ascus the Ascomycetes possess many other kinds of reproductive structures 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. 377, 391, 393. In some instances they are very short, innate; again they are long, loose or fioccose. They may emerge througli stomata singly or in tufts or they may form sporog- PLANT DISEASE FUNGI 89 enous 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 mycelium or they may follow in definite succession regulated by the changes in environment, or again one or more of the spore forms be- longing to the life history of the fungus may be omitted for long in- tervals to appear as the result of stimuli of which little is yet known. an Fig. 80. — Sphserotheca castagnei. Fertilization and develop- ment of the perithecium. Og =oogonium, an = antheridium, st = stalk-cell. 6 as = the ascogonium derived from the oogonium. After Harper. Frequently the conidial stage prevails as a vigorous destructive parasite throughout the growing season while the ascigerous stage appears only during winter or after hibernation, developing only on dead tissue and as a saprophyte. The conidia and chlamydospores are asexual spores. Sexuality in the great majority of Ascomycetes 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 occurs through a trichogyne by spermatia; a mode often met among the lichens. 90 PLANT DISEASE FUNGI In Pyronema, Fig. 83, the carpogoniiim is multi-nucleate and it is fertilized by a multi-nucleate antheridium through a trichogyne. J. ^ 7 n =->a. ■v». ■j-^ C/~ __> O' / Fig. 81. — Boudiera. Six sets of sexual organs. After Claussen. / ■■ J Fio. 82. — Later stage than that of Fig. 81 showing asci and ascophores. After Claussen. Fusion of nuclei is probably in pairs as in Albugo bliti of the Phyco- mycetes. In Boudiera a similar relation is found. Figs. 81, 82. t asc /rjsc Fio. 83. — Pyronema confluens. A. the sex organs, og = oogonium, t = trichogyne. B. fertiliza- tion stage, E. section through young apothecium, asc = asci, asf = ascogenous filament. After Harper. In some Perisporiales an uninucleate oogonium is fertilized by an uninucleate antheridium. Fig. 80. PLANT DISEASE FUNGI 91 The oogonium after fertilization gives rise to a more or less complicated system of ascogenous hyphae, very simple in the Erysiphacese, 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 j^oung ascus usually receives two nuclei from the parent strand of the ascogenous hypha. These nuclei unite giving the primary-ascus-nucleus. This by successive mitoses affords the single spore-nuclei. The spores are cut out from the protoplasm Fig. 84. — Tip of ascus of Erysiphe showing delim- itation of ascospore from ascoplasm by astral rays. After Harper. Fig. 85. — Later stage than Fig. 84, showing well defined spore-wall. After Harper. of the ascus in a most peculiar manner by reflexion of, and union of, astral rays which emanate from a centrosome-like organ at the beak of the prolonged nucleus. Figs. 84, 85. The significance of two nuclear fusions in the life cycle of these fungi, one following the union of the antheridium with the oogo- nium, the other later, in the asci, is a puzzling phenomenon, the real meaning of which is not clear. Key to Subclasses of Ascomycetes Asci with definite number of spores Asci separate or scattered 1. Protoascomycetes, p. 92. Asci approximate, usually forming a hymenium 2. Euascomycetes, p. 94. 92 PLANT DISEASE FUNGI Subclass Protoascomycetes (p. 91) There is a single order, the Saccharomycetales,^ with about seventy species. Mycelium often undeveloped; asci isolated or formed at different points on the mycelium, mainly 4-spored; spores unicellular; asexual reproduction by gemmation or by conidia. Key to Families of Saccharomycetales Vegetative cells single or loosely attached ill irregular colonies, mycelium not usually developed, asci isolated, not differentiated from vegetative cells. . 1. Saccharomycetaceae, p. 92. Vegetative cells forming a mycelium, asci terminal or intercalary, differen- tiated from mycelium 2. Endomycetaceae, p. 93. Fig. 86. — Yeast plant-bodies, showing bud- ding and sporulation. After Coulter and Rees. The first family, the yeasts, to which belong the majority of the species of the order, is of prime importance in fermentation. A few species are known to cause animal diseases; others are found asso- ciated with the slime fluxes. Saccharomycetaceae ^ Vegetative cells separate or few together, never truly filamentous, propagating by buds; asci globose to elliptic, 1-4, rarely 8 to 12- spored; growing typically in sugary or starchy materials. Nematospora Peglion Colonies (in culture) disciform; cells elongate; asci cylindric, 8-spored; spores filiform, continuous, long-ciliate, hyaline. N. coryli Pegl., the cause of malformation of the hazel nut is a peculiar fungus with what appears to be asci containing eight, long, slender, flagellated spores. ^ Guillermond, A. The Yeasts. Trans, by F. W. Tanner. John Wiley and Sons, London, 1920. PLANT DISEASE FUNGI 93 N. phaseoli Wingard ^ Elliptical cells in young cultures vary in length from 8-14 ix and in diameter form 6-10 //. The mature spherical cells are 20/i in diameter and the mycelium-like strands from 90-140 x 2.5- 3.5 M- Asci and ascospores are produced in great numbers in the lesions on Lima bean seed. They are cylindrical with rounded ends, 60-85 x 10-12 ix] ascospores, 8, in two groups of 4, 40-46 x 2.5-3 IX, slender, 1 -septate, slightly ridged at septum, apex acute, base extended into a slender, non-motile whip which averages about one and one-fourth times the spore length. Endomycetaceae (p. 92) Mycelium usually well developed, often producing a luxuriant growth, multiseptate; asci borne singly on branches or intercalary, 4 to 8-spored; spores one-celled; conidia produced apically, unicel- lular. Endomyces Rees Mycelium well developed, byssoid; asci asexually produced, borne singly on the ends of short lateral branches, globose to pyri- form, 4-spored; spores continuous. The members of this genus are of ques- tionable importance as parasites. Some are commonly found in sap exuding from tree wounds where they, together with other Fig. 87.— Young" asci of e. fungi present, set up a fermentation the ThL'TiZtlwJ"'"" '""^ products of which prevent the wound from healing and result in injury. One species has been reported in America as an active parasite on apples. E mali Lewis ^ Mycelium well developed, multiseptate; co- ^ TypfcarnSnneT^of ^^^^i^ formcd ou short couidiophores or on the agarl'^Af'te^Liwir ^^^^ ^^ ^^^^^ §®^^ ^^^^cs, averaging 3 X 8 m; no yeast-like budding; asci usually on short lateral branches, 11-14 yu in diameter; ascospores sphseroidal, slightly elongate, 4.5 x 5.5 ix with thickened places on the walls, brown when mature. Figs. 87, 88. 1 Wingard, S. A. Yeast-Spot of lima beans. Phytoph. 12: 525, 1922. 94 PLANT DISEASE FUNGI Euascomycetes (p. 91) This is an extraordinarily large group comprising some 16,000 species, with great variety of size, color and shape of plant body. Most of them are saproph3^tes, still many are parasites either in their ascigerous or their conidial stages of development. The twelve orders of chief interest as plant parasites are given in the following key. Key to Orders of Euascomycetes Asci approximate in an indefinite hyme- nium, no ascoma 1. Protodiscales, p. 95. Asci grouped in a definite ascoma Asci collected in a flattened, concave or closed ascoma, often bordered by a distinct layer Ascoma at maturity open and more or less cup-like. Discomycetes Ascoma open from the first, cla- vate or convex, pitted, or gy- rose 2. Helvellales, p. 99. Ascoma at first closed, opening early, without special cover- ing, more or less fleshy 1. Pezizales, p. 100. Ascoma opening tardily, enclosed by a tough covering which be- comes torn open at the matur- ity of the spores Ascoma roundish, opening by stel- late or radiating fissures. ... 4. Phacidiales, p. 115. Ascoma elongate, opening by a longitudinal fissure 5. Hysteriales, p. 120. Asci collected in a cylindric, globose or dimidiate perithecium Perithecia sessile, solitary and free, or united and embedded in a stroma Asci arranged at different levels in the perithecium Not stromatic 8. Aspergillales, ]). 122. Stromatic 7. Myriangiales, p. 125. Asci arising from a common level Mycelium superficial, perithecia scattered, globose and with- out typical ostiolc 8. Perisporiales, p. 127. PLANT DISEASE FUNGI 95 Mycelium not superficial, locules without typical ostioles... 9. Dothideales, p. 154. Mj^celium immersed or superficial, perithecia ostiolate Perithecia dimidiate 10. Hemisphaeriales, ^ p. 145. Perithecia not dimidiate Perithecia and stroma (if present) fleshy or mem- branous, bright colored. 4. Hypocreales, p. 145. Perithecia and stroma (if present) hardened, rarely membranous, dark col- ored 12. Sphaeriales, p. 157. Protodiscales (p. 94) The 4-8 to many-spored asci form a flat palisade-like hymenium which arises directly from the mycelium; paraphyses none; spores, one-celled, elliptical or round. Exoascaceae This family is distinguished from the other family of the order by its parasitic habit. It is the most simple of the parasitic As- comycetes, definitely recognizable as such, and is comparable with Exobasidium among the Basidi- omycetes. (See p. 287). All the species are parasitic and many of them injurious. The mycelium which can be distinguished from that of other fungi by its cells ot irregular size and shape, wanders between the living host cells (intracellular in one species), or is sometimes limited to the region just below the cuticle. The asci develop in a palisade form on a mycelial network under the epidermis, or the cuticle, or on the ends of hyphse arising from below the epidermal cells. They are exposed by the rupture of the cuticle or epidermis and contain four to eight hyaline, oval, one-celled spores. These by budding, while still in the ascus, may produce numerous secondary spores, conidia, which give the impression of a many-spored ascus. iTheissen and Sydow, Synoptische Tafeln, Ann. Myc. 15: 389, 1917. Fig. 89. — Taphrina showing mycelium and asci. After Atkinson. 96 PLANT DISEASE FUNGI The ascospores also bud freely in nutritive solutions. The primary- ascus-nucleus arises from fusion of two nuclei as is general among the Ascomycetes. The spore-nuclei arise by repeated mitoses of the primary nucleus. Affected leaves, fruit and twigs become swollen and much dis- torted; wrinkled, curled, arched, puckered. In woody twigs the mycelium often induces unnatural, profuse, tufted branching resulting in "witches brooms" though such structures often arise from irritation due to other causes. Many attempts have been made to arrange the species in natural genera; some based on the number of ascospores, others largely on the biologic grounds of annual or perennial my- celium. Giesenhagen whose classification is followed here, recog- nizes two genera, Exoacus being merged into Taphrina. Taphrina Fries Mycelium annual or perennial; asci 4 to 8-spored, or by germina- tion of the ascospores, multispored, borne on the surface of blisters and other hypertrophied areas, cylindric to clavate, or a modifica- tion thereof. Of this genus Giesenhagen recognizes four series of species which are arranged in three subgenera. The fungus is best studied when the asci are mature but may usually be recognized by its mycelial characters. Subgenus 1, Taphrinopsis, is parasitic on ferns. Subgenus 2, Eutaphrina, is found on Amentacese, chiefly Betula, Alnus, Ostrya, Carpinus, Quercus, Populus. Fig. 90. — Taphrina showing mitoses in the young ascus leading to the development of spore-nuclei. After Ikeno. Subgenus 3. Exoascus, — two series Asci clavate, normally cylindric or more or less abbreviated. (1) Prunus series on Rosaceae. Asci slender, clavate, narrowed below, broadest in the upper fourth, varying through all inter- mediate forms to narrowly cylindric. PLANT DISEASE FUNGI 97 (2) /Esculus series, on Sapindacese, Anacardiaceae, etc. — Asci broadly cylindric, short, rounded or truncate. The more important economic species of the genus belong to the Prunus series. T. deformans (Fcl.) Tul. The irregular vegetative mycelium devoid of haustoria grows in the leaf parenchyma and petiole and in the cortex of branches of the peach. A dis- tributive mycelium lies close beneath the epidermal cells of twigs and in the pith and extends some distance through the twig. Fig. 91. Branches arise from the vegetative my- celium, penetrate be- tween the epidermal cells to the cuticle and then branch freely to form a network of short, distended cells beneath the cuticle. This is the hymenium, a layer of ascogenous cells. These cells elon- gate perpendicularly to the host's surface. Fig. 89, rupture the cuticle, and form a plush-like layer. The protoplasmic contents crowd toward the tips of these cells and a basal septum cuts off f ho QcmiQ ■nm-nt^Y' fi^nriT Fig. 91. — T. deformans. 5, distributive hypha; 1, vegeta- tne dbCUb pioper IlOm ^.^^ hyphse; 9, sporiferous hyphge. After Pierce. the stalk cell. Fig. 92. The spores then form within the ascus. The ascospores may bud either before or after extrusion from the ascus, producing conidia, which may themselves bud indefinitely, producing secondary, 98 PLANT DISEASE FUNGI tertiary, etc., crops. In this condition the conidia strongly re- semble yeast cells. On the host plant ascospores germinate by germ tubes which are capable of infecting proper hosts. No suc- cess has rewarded attempts to secure germ tubes from conidia. Leaf infection is chiefly external; rarely internal from mycelium perennating in the twigs. It occurs when the leaf is very young. Infected leaves are thickened and broadened and the tissues are stiff and coriaceous. The palisade cells in- crease in size and num- l^er and lose their chlo- rophyll. Blistering and reddening of the leaves follows. Asci clavate, 25-40 x 8-1 1 At ; spores 8, subglo- bose or oval, 3-4 /z. T. pruni (Fcl.) Tub, on plum and wild cherry, causes " plum pockets." The ovary is the seat of attack. The mycelium after bud in- fection pervades the mesocarp which hyper- trophies and alone pro- duces a much enlarged Fig. 92. — T. deformans. Young and old asri: 1, 2 asd with fmif- ncmQll-^T- -vArifVi or> spores; 10, a young and an old ascus; 15, the young ^^/^^^ USUaiiy VVILU en- hymenial layer showing asci of various ages, a to c. tire SaCriflCC of tllC Other After Pierce. r -j , a • iruit parts. Asci are formed over the diseased surface much as in the last species. The mycelium is perennial in the bast and grows out into the new shoots and buds each spring. Infection also reaches other shoots and trees by means of the spores. Ascus elongate-cylindric; 30-60 x 8-15 /x; spores 8, globose 4-5 ix. Perennial. T. cerasi (Fcl.) Sad. produces the witches broom effect upon cultivated and wild cherries. It is common in Europe, rare in America, perennial; asci clavate, 30-50 x 7-10 /x; spores 8 forming conidia in the ascus, oval, 6-9 x 5-7 ix. On Prunus avium, P. cerasus, etc. f^. -ir-€T^t PLANT DISEASE FUNGI 99 T. communis (Sad.) Gies. Spores on immature friuts; asci clavate, 24-45 x 5-10 ix; spores 8, elliptic, 5 x 3-4 ix, often produc- ing conidia. On Prunus americana, P. maritima, P. nigra, and P. pumila pro- ducing "plum pockets." When spores infect the fruit the myce- lium is at first confined to the epidermis. This fungus was thought to be perennial in the branches, but apparently often is not so since spraying gives control. T. decipiens (Atk.) Gies., causing leaf curl, T. farlowii (Sad.) Gies., T. mirabilis (Atk.) Gies., T. longipes (Atk.) Gies., T. rhi- zipes (Atk.) Gies., T. institiae (Sad.) Joh. are other species on Prunus. T. buUata (Fcl.) Tul. is on pear and Japanese quince; T. cra- taegi (Fcl.) Sad. on Crataegus oxyacantha. Helvellales (p. 94) Ascoma fleshy, separable into a definite hymenium of asci and paraphyses; stroma usually large and stalk-like, fertile portion more or less cap-like; hymenium free from the first or covered with a thin, evanescent veil; asci cylindric, opening by an apical pore; spores ellipsoid, colorless or light yellow, smooth, or in one genus echinulate. Rhizinaceae Ascocarp sessile. Rhizina Fries Spores elliptic or spindle-shaped, ascophores with rhizoid-like struc- tures. Some eight species are recog- nized by their crust-formed, sessile, flat ascophore with root-like out- growths from the lower side. Fig. 93. Asci cylindrical, 8-spored, opening by a lid; spores one-celled, hyaline; par- aphyses many. It is often purely saprophytic, growing in burned-over forest areas. R. infiata (Schaff.) Quel, is counted as the cause of serious root diseases of forest trees, especially conifers, in Europe. R. undulata Fr. causes death of fir seedlings and other conifers. Fig. 93. — Rhizina infiata. B, ascocarp from below; C, asci and paraphyses. After Schroter and Tulasne. 100 PLANT DISEASE FUNGI Pezizales (p. 94) In this order, unlike the last, the hymenuim is at first enclosed but soon becomes exposed. The apothecia at maturity are typi- cally disc or saucer shaped (Fig. 101) or sometimes deeper, as cup, beaker, or pitcher-shaped. They vary from a size barely visible up to 8-10 cm. in diameter. Some are stalked, more often they are sessile. In consistency they vary from fleshy or even gelatin- ous to horny. Paraphyses are present and may unite over the asci to form a covering, the epithecium. The apothecium may be differentiated into two layers; the upper bearing the asci is the hypothecium, the lower the peridium. In some cases sclerotia are formed. Many species possess conidiospores as well as asco- spores, borne either on hyphse or in pycnidia. The great majority are saprophytes, a few are parasitic. There are some three thou- sand species. Key to Families of Pezizales No lichenoid thallus; ascocarps free, solitary or cespitose, fleshy or waxy, rarely gelatinous; ends of paraphyses free; peridium forming a more or less differentiated membrane Peridium of elongate, parallel pseudo-paren- chymatous, hyaline, thin- walled cells. ... 1. Helotiaceae, p. 100. Peridium firm, of roundish or angular, pseudo- parenchymatous, mostly dark, thick- walled cells 2. MoUisiaceae, p. 110. Ascocarps leathery, horny or cartilaginous; ends of the paraphyses united into an epithecium ; peridium .well developed, mostly leathery or horny; ascocarps at first embedded in a matrix, then erumpent, urceolate or cup- shaped, at first enclosed in a membrane which disappears later 3. Cenangiaceae, p. 114. Helotiaceae (p. 100) In members of this family there is a distinctly differentiated peridium. The apothecia are usually fleshy or waxy, superficial, first closed, later opening; the paraphyses form no epithecium. Asci 8-spored. Spores round to thread-shaped, one to 8-celled, hyaline. Some of the genera are among the most serious of plant pathogens. PLANT DISEASE FUNGI 101 Key to Genera of Helotiaceae Ascocarps fleshy, fleshy-waxy, thick or mem- branous Ascocarps fleshy-waxy, brittle when fresh, leathery when dry, not setose, spring- ing from a sclerotium 1. Sclerotinia, p. 101. Ascocarps waxy, thick, tough or mem- branous; externally hairy, without arachnoid mycelium; spores ellipsoid or elongate; disk smooth; paraphyses obtuse at the apex. Walls of ascoma delicate; spores mostly l-cefled, rarely 2-celled at maturity. 2. Dasyscypha, p. 108. Walls of ascoma thick ; spores 2-celled at maturity 3. Lachnella, p. 109. Ascocarps naked, not from sclerotia; spores ellipsoid or fusiform, 1-celled; border of disk smooth 4. Hymenoscypha, p. 109. Sclerotinia Fuckel This genus contains several very important pathogens, some of them preying upon a wide range of hosts and causing great loss. A striking feature of the genus is the sclerotium which is black and borne within the host tissue or upon its surface. From the sclerotia after a more or less protracted period the apothecia develop. These are disc-shaped and stalked. The asci are 8-spored; spores ellipti- cal or fusiform, unicellular, hyaline, straight or curved. Some species possess Botrytis forms (see pp. 385-6), others Monilia (see p. 379) forms of conidial fructification. In addition to these there may be gonidia, which appear to be degenerate, function- less conidia. In some species there is no known spore form except that in the ascus. S. ledi Naw. is of especial interest as the one fungus outside of the Uredinales that exhibits heteroecism. Many forms found upon distinct hosts and presenting slight or even no microscopic differences, have been named as separate spe- cies. Only long careful culture studies and inoculation experiments will determine which of these species are valid, where more segre- gation, where more aggregation is needed. The mere association of Botrytis or Monilia conidial forms with Sclerotinia, in the same host, has repeatedly led to the assumption 102 PLANT DISEASE FUNGI Fig. 94. — S moniliform urnula, conidia that such forms were genetically connected. Such assumptions are not warranted. Only the most careful study and most com- plete evidence justify such conclusions. S. cinerea, S. fructigena, and S. laxa. These forms are perpetuated chiefly by their conidia. The ascus-forms are much less often seen. When the conidia fall upon the peach, the mycelium develops and penetrates even the sound skin, then rapidly induces a brown soft rot. The mycelium within the tissue is septate, much branched, and light brown in color. It soon proceeds to form a subepidermal layer and from this the hyphse arise in dusty tufts of Monilia-f orm conidiophores and conidia (Fig. 95) . The earlier conidia are thin-walled and short lived, the later ones thicker walled and more enduring. After some weeks these tufts cease forming ter woron^nl^"^^' ^^' ^^^ disappear. The mycelium within the fruit persists, turns olivaceous and forms large irreg- ular sclerotioid masses which on the following spring may pro- duce fresh conidia. These sclerotioid (mummified) fruits under suitable conditions in nature, usually at blossom time of the host, can also produce apothecia. These apothecia develop in large numbers from old fruits half buried in soil, and send forth ascospores to aid in infection. The ascospores germinate readily in water and it was proved by Norton that they give rise to mycelium which produces the characteristic Monilia. Inoculation of ascospores on fruit and leaves also gave positive results in two or three days. The flowers, and through them the twigs, are also invaded by the mycelium which seeks chiefly the cambium and bast. Shot-hole effect is produced on leaves of peach and cherry. Infection frequently occurs through minute wounds. On the apple the fungus shows two different modes of develop- ment. In some cases the mycelium accumulates under the epider- mis without producing spores, becomes dark colored and also causes a darkening of the contents of the host cells, which re- sults in a black spot giving rise to the name black rot. In other PLANT DISEASE FUNGI 103 cases the mycelium produces a brown rot and abundant conidlal tufts, arranged in concentric circles around the point of in- fection. The form on pomaceous fruits has long been regarded as identi- cal with that on stone fruits, but recently, at least in Europe, they have been differentiated on cultural and morphological grounds, as separate species, the most distinctive character perhaps being Fig. 95. — Sclerotinia on plum, a, section showing a spore pustule and chains of conidia; b, part of a spore-chain; c, spores germinating; d, a mummy plum and as- cophores; e, an ascophore; /, ascus; g, mature spores. After Longyear. the color of the mass of conidia. In a similar way S. laxa Ad. & Rhul. is set aside as a distinct species infecting only apricots. From extended cultural studies Matheny concludes, "The American brown rot occurring on stone fruits is not identical with S. fructigena occurring in Europe on pome fruits. It agrees more nearly with S. cinerea and should be referred to that species. " S. cinerea (Bon.) Schr.^ Apothecia and asci similar to those of S. fructigena, conidia = Monilia cinerea Bon. Conidiophores covering the fruits with a dense, grayish mold-like growth; spores averaging 12.1 x 8.8 ju. On stone and pome fruits. Cankers are also produced on spurs and branches. ^ Matheny, W. A. A comparison of the American brown-rot fungus with S. fructi- gena and S. cinerea of Europe. Bot. Gaz. 56: 418, 1913. 104 PLANT DISEASE FUNGI S. fructigena (Pers.) Schr. Apothecia from sclerotia produced either in or on mummied fruits, 0.5-3 cm. high, stem dark brown, disk lighter, 5-8 or even 15 mm. in diameter; asci 125-215 x 7-10 /jl; spores ellipsoidal, 10-15 X 5-8 fjL. Conidia = Monilia fructigena Pers. Conidiophores covering the fruits of the host with a dense, mold-like growth of light brownish- yellow or ochraceous color; spores averaging 20.9 x 12.1 jj,. On stone and pome fruits, especially the latter, in Europe and pos- sibly in America. S. seaveri, Rehm., conidia = Monilia seaveri, on Prunus serotina, causes twig blight. S. padi Wor. is found on Prunus padus and Castanea. Fig. 96. — S. sclerotiorum. Solerotia prodticed in artificial culture. After Stevens and Hall. It possesses a Monilia-form conidial stage with typical disjunc- tors, i. e., spindle-shaped cellulose bodies between the conidia which easily break across to facilitate the separation of the conidia. S. oxycocci Wor. is on cranberry. It is unique in that half of the spores in each ascus are larger than the others. The conid- ial stage is a Monilia. PLANT DISEASE FUNGI 105 S. sclerotiorum (Lib.) Mass. = S. libertiana FcL^ Sclerotia from a few millimeters up to 3 cm. in length, black apothecia scattered, pale, 4-8 mm. or more broad, stem slender asci cylindric, 130-135 x 8-10 ^i, apically very slightly bluish spores ellipsoid, usually minutely guttulate, 9-13 x 4-6.5 /x; par- aphyses clavate. This fungus affects numerous hosts. Among the most impor- tant on which it causes serious disease are lettuce, ginseng, bean, cucumber, carrot, celery, potato, parsley, hemp, rape, lemon, various bulbs, zinnia. Columbine, Antirrhinum, petunia. The white mycelium is found superficially and within the host, espec- ially at places where moisture is retained, as between leaves, at leaf axils, etc., also within plant cavities. Microscopically it con- sists of long cells branching in a rather characteristic way. Fig. 98. Within the host tissue the hyphal threads are thicker, richer in protoplasm, more septate, and much more branched and crooked than outside of the host. Aerial hyphal filaments when they touch a solid repeatedly branch in close compact fashion forming the attachment organs. Upon the exhaustion of the food supply and the consequent termination of the vegetative period the mycelium becomes very Fig. 97. — S. sclerotiorum. Scle- rotia and apothecia. After Stevens and Hall. Fig. 98. — Mjcelium showing septation and branching. After Stevens and Hall. dense in spots and within these clumps of mycelium the sclerotium forms; at first white, later pink, finally smooth and black (Fig. 97). They are often found in the leaf axils (lettuce), in the pith of stems (carrot), etc. Under some conditions, as on unsuitable nutrient media, gonidia are produced. The sclerotia can germinate at once or remain dormant for one, perhaps several years. On germination they send forth ^ Wakefield, E. M. On the names Sclerotinia sclerotiorum (Lib.) Massee, and S. libertiana Fuckel. Phytop. 14: 126, 1924. 106 PLANT DISEASE FUNGI from 1 to 35 negatively geotropic sprouts which grow to the soil surface unless that be more than about 5 cm. distant. On reaching the light the apex of the sprout thickens and soon develops its apothecium; at first inverted-conical, soon flat, and finally somewhat revolute. Changes in atmos- pheric humidity cause the discharge of ascospores in white clouds. The ascospores germinate readily but the resulting mycelium is of such small vigor that it is incapable of parasitism. If the ascospore germinates where it can maintain a saprophytic life until a vigorous mycelium is developed then the mycelium may become parasitic. Both ascospores and mycelium are compara- tively short-lived. The mycelium can migrate but a short distance over soil. No form of co- nidia except the apparently functionless gonidia is produced. It has been repeatedly claimed that this fun- gus possesses a Botrytis conidial stage, but the results of much careful work deny this. Tests by Westerdijk indicate the absence of such biologic specialization in regard to hosts as is found in Erysiphe and elsewhere. S. perplexa Lawrence ^ Ascophores rare to very numerous and dense, naked, smooth, pale flesh colored, saucer-shaped, stipitate, 2-8 mm. broad, stipe 1-2 mm. long; asci cylindrical, 115-145 x 5-7 /x, 8-spored; spores elliptical, hyaline, 1-celled, 8-10.5 x 3.5-5 n; paraphyses simple, slender, cylindrical, non-septate; sclerotia grey, later dull black, snow-white within, to pink or brown with age, round, 1-3 mm. in diameter or smaller, tuberiform, or forming thin, black crusts, 1-115 mm. in length, giving rise to ascophores or conidiophores or both; conidiophores densely tufted and woolly, greyish brown, straight and uniform below, slightly irregular above, 2-3-10 mm. tall, dichotomously and sparingly forked, the branches long and wide-angled, conidia broadly obovate, or elliptical, slightly trun- cate at base, 8-15 x 6-10 fx. The cause of rot of Jerusalem artichoke, sunflower, onion, cucumber, chicory, cabbage, rutabaga and other crucifers. Fig. 99. — S. sclerotio- rum, asci and para- physes. After Ste- vens and Hall. ^ Lawrence, W. H. Plant diseases induced by Sclerotinia perplexa n. sp. Wash. Agr. Exp. Sta. Bull. 107, 1912. PLANT DISEASE FUNGI 107 S. ricini Godfrey. Apothecia one to several from a single sclero- tium, 5-30 mm. high, infundibuUform to cyathiform and dis- coid, long stipitate, cinnamon brown to chestnut brown, disc at first closed, expanding to saucer-shaped with margin sometimes recurved, exterior roughened, 1-7 mm. in diameter; asci cylin- drical to cylindro-clavate, apex slightly thickened, opening by a pore, 50-110 fx x 6-10 m; spores 8, ellipsoidal, hyaline, continu- ous, biguttulate, 9-12 x 4- 5 m; paraphyses abundant, filiform, septate, hyaHne, 1.5-2 fx in diameter. Conidial stage (Botrytis sp.) forming a widespread cobwebby or somewhat woolly mass, pale drab-gray; sterile hyph^e procumbent, hyaline, many-septate, often vacuolate, frequently anastomosing, fertile hyphae long, slender, smooth, slightly constricted at the base, olivaceous when mature, dichotomously branched; conidia borne on sterigmata, globose, smooth, hyaline, 6-12 /x, compactly grouped; microconidia globose, hyaline, 2-3.5 m, borne apically on short conidiophores that develop on the sides of hyphse or on tips of special branches; appressoria rare, 20-60 /x across base. Sclerotia black, rough, elongate, irregular, 1-25 mm. in length. Parasitic on Ricinus communis, usually on inflorescences, also on stems and leaves. S. minor Jagger.^ Apothecia one, rarely more, from a sclerotium; disk 0.5-2 mm. in diameter; asci 125-175 x 8-11 /x, 8-spored; spores 5-9 x 8-20 fx. Paraphyses filiform; gonidia globose, hyaline, 3^ m, on short, obclavate conidiophores; sclerotia black, 0.5-2 mm. in diameter. Parasitic on lettuce and celery. The decay is similar to that produced by S. sclerotiorum. S. smilacina Dur., = S. panicis Rankin, is described as parastic on the rhizomes of ginseng causing a black rot. Sclerotia 0.3-1 cm. black; asci 125-137 x 6.4 fx; spores 11.7-16 X 4.8-7.5 M. S. nicotianae Cud. & Kon. parasitizes the leaves and stems of tobacco. It is possibly identical with S. sclerotiorum. ■■■■B^ii^npr^^^j^^H ^■1' ' ^H ^^B'' *^''^*<' ""' ^^H ^^Hk\. ' i^^i ^^^^^B *^^^^H ^H' 9h FiQ. 100.— Cultures of Scle- rotinia from tobacco on po- tato agar, showing sclerotia. After Clinton. ^ Jagger, J. C and other crops. Sclerotinia minor, n. sp. The cause of a decay of lettuce, celery Jour. Agr. Res, 20: 331. 1920. 108 PLANT DISEASE FUNGI S. trifoliorum Erik. In general this resembles S. sclerotiorum with which it is by some regarded as identical. The sclerotia, varying in size from that of a mustard seed to a pea, are found in the decayed tissue, or as larger, flat, surface sclerotia. There are no conidia except the functionless gonidia. On clover and alfalfa. S. bulborum (Wak.) Rehm, which is very similar to S. trifo- liorum and without known conidia, grows on hyacinth, crocus, scilla and tulip. Cross infections between hyacinth and clover have not been successful and the species may be distinct. Several other species of the genus are found on Ericaceae, Betulacese, Rosaceae, Gramineae, etc. This phytic Dasyscypha Fries (p. 101) is a genus of some one hundred fifty species, mostly sapro- but, sometimes parasitic on twigs. The apothecia are small, short-stalked or sessile, waxy or membranous, bright colored in the disk, with mostly simple hairs on the out- side and margin. Asci cylindrical or clavate, 8-spored; spores ellipsoid or fusiform, hyaline, 1-celled, rarely 2- celled, sometimes guttulate; paraphyses blunt, needle- like. D. willkommii Hart, causes a serious larch disease and affects also the pine and fir. The stromata appear as yellowish-white pustules on the bark soon after its death. Here hyaline conidia are produced on the open surface or in cavities. Apothecia B Fig. 101. — D. willkommii. A, natural size and single apothecium enlarged; B, an ascus. After Lindau. 2-5 mm. broad appear later. The ascospores can infect wounds; the conidia seem to be functionless. The mycelium spreads through the sieve tubes, intercellular spaces, and xylem to the pith. Apothecia short-stalked, yellowish without, orange within; asci 120 X 9 m; spores 18-25 x 5-6 fx; paraphyses longer than the ascus. PLANT DISEASE FUNGI 109 D. resinaria Rehm is a wound parasite much like the above in its effects. It occurs chiefly on spruce and larch but sometimes also on pine. Ascophores upon cankers on branches and trunk of the host are very similar to those of the preceding species but with more evi- dent stipe and paler disk; spores very minute, subglobose, 3x2- 2.5 tx] conidia 2 x 1 /x. Other species are found on spruce, pine, and other conifers. Lachnella Fries (p. 101) This is similar to the last genus but with the apothecia usually sessile and the spores usually 2-celled at maturity, and in two rows in the ascus. There are about forty species. Fig. 102. — Lachnella. F, habit sketch; G, ascus and paraphyses. After Rehm. Fig. 103. — Hymenoscypha. J, habit sketch; K, ascus and paraphyses. After Rehm. L. pini Brun. injures pine twigs. The apothecia are brown out- side; the disc reddish-yellow with a white margin. Ascoma short-stipitate, 5 mm. in diameter, pale brown; disk hght orange-red with a pale margin; asci 109 x 8-9.5 m; spores 19- 20 X 6.5-8.5 II, hyaline. Hymenoscypha Fries (p. 101) This genus of over two hundred species is mainly saprophytic. Ascoma sessile or short-stipitate, usually smooth; asci cylindric no PLANT DISEASE FUNGI to globoid, 8-spored; spores elliptic, blunt to pointed, hyaline; paraphyses filamentous, apically enlarged, hyaline. H. tumulenta P. & D., in its conidial stage as Endoconidium, affects rye grain causing it to shrivel and assume poisonous prop- erties. The conidia are borne endogenously in the terminal branches of the hyphse and escape through an opening in the end of the branch. Mollisiaceae (p. 100) Ascocarp fleshy, waxy, are rarely membranous, bright colored, at first sunken in the substratum and later slightly erumpent, at first more or less globose, becoming flattened; asci 8-spored, open- ing by a slit; spores hyaline, 1 to many-celled; paraphyses slender. There are above four hundred species. Key to Genera of the Mollisiaceae Ascocarps bright colored, only slightly erum- pent Spores ellipsoid or elongate, rounded, 1-celled 1. Pseudopeziza, p. 110. Spores becoming 2 to 4-celled Apothecium developed within or on an exposed stromatic subiculum 2. Neofabraea, p. 111. Apothecium on a covered subiculum 3. Fabraea, p. 112. Ascocarps dark colored, at length strongly erumpent; externally smooth, the margin at most merely shredded; spores ellipsoid or fusiform, 1-celled 4. Pyrenopeziza,p. 113. Pseudopeziza Fuckel The genus comprises some ten species, all parasitic on leaves, several of them upon economic plants causing serious disease. The very small apothecium develops subepidermally breaking through only at maturity, light colored; spores 1-celled, hyaline, in two ranks in the ascus; paraphyses somewhat stout, hyaline. Conidial forms are found in Gloeosporium, Colletotrichum and Marssonina. P. medicaginis (Lib.) Sacc. The epiphyllous apothecia are in the older leaf spots, subepider- mal at first but eventually breaking through. Apothecia saucer-shaped, light colored, fleshy; asci clavate; spores hyaline, 10-14 jj, long; paraphyses numerous, filiform. On dead spots in leaves of alfalfa and black medick. PLANT DISEASE FUNGI 111 «3 Fig. 104. — P. trifolii. Ascus and paraphyses; germinating spores. After Chester. P. trifolii (Bernh.) Fcl. This species on Trifolium is closely related to, perhaps identical with, the last species. P. ribis Kleb. Apothecia appear in the spring on dead leaves of the previous season; saucer- shaped, fleshy, somewhat stalked; asci clavate, spores hyaline, ovoid ; paraphyses simple or branched, slightly clavate, rarely septate. Conidial phase ( = Gloeosporium ribis) on the leaves of the host forming an abundant amphigenous infection; acervuli stro- matic; conidiospores commonly 19 x 7 m, varying from 12-24 x 5-9 n, escaping in gelatinous masses. On red and white currants, less commonly on black currants and gooseberries. The ascigerous stage of this fungus was demonstrated by Kle- bahn in 1906 to be genetically connected with what had been earlier known as Gloeosporium ribis. Old leaves bearing the latter fungus were wintered out of doors in filter paper and in the spring an ascigerous stage was found. The ascospores were isolated, grown in pure culture and typical conidia were produced. The ascospores also infected the host leaves successfully, producing there the typical Gloeosporium. The co- nidial stage is the only one ordinarily seen. The acervuli are subepidermal elevating the epidermis to form a pustule which eventually ruptures and allows the spores to escape as a gelatinous whitish or flesh-colored mass. The spores are curved and usuallv larQ;er at one end than at the other. Fig. 105. — P. ribis. Apothecium in section. After Klebahn. Neofabraea Jackson^ (p. 110) Characteristics in general those of Pseudopeziza; apothecia de- veloping in, and at length breaking forth from, a more or less ex- 1 Jackson, H. S. Ore. Agr. Exp. Sta. Bienn. Crop Pest Hort. Rept. 1911-12, 178. 112 PLAN't DISEASE FUNGI posed subiculum consisting of the old conidia-bearing stroma. Spores at first one-celled; at length two to four celled. N. malicorticis (Cordley) Jackson Apothecia 0.5-1 mm. in diameter, light brown, waxy, at first concave, then flat and finally convex, surrounded at the edge with the black remains of envelop- ing layers. Developing within and bursting forth from a sub- iculum consisting of the old conidia stroma. Asci clavate, 90-100 M long, 10.5-13 /x broad; spores colorless, one-celled or becoming four-celled on ger- mination, 16-19 /x long by 5-7 /x broad, elliptical, slightly flat- tened on one side, uniseriate; paraphyses simple or branched, septate, tips slightly swollen. Developing in the autumn in cankers formed during the pre- vious season. Conidia ( = Gloeosporium malicorticis) . Caulicolous; spots brownish, slightly depressed, irregular in outline; acervuli minute, erum- pent; conidia elliptic, curved, hyaline or greenish-tinged, granular, 24 x 6 /x. On apple and quince branches and twigs causing canker, also on fruit causing rot. The spots begin in the bark in autumn, soon reaching to the cambium where they extend rapidly, the fungus reaching to some extent into the sap and even the heart wood. In the following midsummer acervuli appear. Fabraea Saccardo (p. 110) This genus of small leaf parasites much resembles Pseudopeziza but differs from it in its 2 to 4-celled spores; paraphyses hyaline. F. maculata (Lev.) Atk. The perfect stage is common on pear and quince leaves which have wintered naturally. When such leaves are wet, the white Fig. 106. — N. malicorticis; a, acervulus; E, ger minating spore. After Cordley. PLANT DISEASE FUNGI 113 8-spored asci may be seen crowding through the surface in small elliptical areas. The apothecium is paraphysate; the spores hya- line and 2-celled. Conidial form ( = Entomosporium maculatum) on leaves and fruits; aceruvli, black, subepidermal, the epidermis breaking away to expose the spore mass; spores hyaline, 18-20 x 12 /*, 4 cells in a cluster, the lateral cells smaller, depressed; stipe filiform, 20 x 0.75 n; the other cells with long setae. Atkinson proved the connec- tion of the ascigerous with the conidial form by cultivating the conidia from the ascospores. The conidial form is very common and destructive on pear and quince leaves and fruit. The Fig. 107.— F. maculata. l, acervulus of co- nidial stage in section; 3, spores. Southworth. After mycelium which abounds in the diseased spot is hyaline when young, dark when old. It collects to form a thin subcuticular stroma. On this the spores are produced on short erect conidio- phores, Fig. 107; eventually the cuticle ruptures and the spores are shed. The spores germinate by a tube which arises near the base of a bristle. Pyrenopeziza Fuckel (p. 110) P. medicaginis Fcl.^ Apothecia sessile on stromata, 0.25-1 mm. in diameter, outer wall black; paraphyses 50-80 x 2.5-3 n; asci 60-70 x 10 /x; spores ovoid, 8-11 X 5-6 jjl. Conidia (=Sporonema phacidioides Fcl.) in acervuli; conidio- phores bottle-shaped, 12-14 x 3 /x; conidia cylindrical, slightly bent, 5-9 x 2-3 ^u. On alfalfa causing yellow leaf spots. The mycelium is both in- ter- and intracellular, in late stages filling the parenchyma cells. The acervuli develop subepidermally in the living host tissue; the ascigerous stage on dead tissue. Inoculations with ascospores gave positive results in about two weeks, but conidia failed to do so. ^ Jones, F. R. Yellow-leaf blotch of alfalfa caused by the fungus Pyrenopeziza medicaginis. Jour. Agr. Res. 13: 307, 1918. 114 PLANT DISEASE FUNGI Fia. 108. — Conidial stage of P. medicaginis. After Jones. Fig. 109. — P. medicaginis, section showing asci. After Jones. Cenangiacese (p. 100) Ascoma at first buried, later erumpent, on a stroma, dark, with a rounded or elongate disk; asci 8-spored; spores long or filiform, 1 to many-celled, often muriform, hyaline or dark; paraphyses branched forming a complete epithecium. About two hundred fifty species. PLANT DISEASE FUNGI 115 Fig. 110. — Cenangium, habit sketch, asci and pa- raphyses. After Tulasne. Cenangium Fries Parasitic or saprophytic, chiefly in bark, the apothecium devel- oping subepidermally and later breaking through to the surface; sessile, light colored without, dark within; asci cylindric-globoid, 8-spored; spores eUipsoid, 1 or rarely 2-celled, hya- line or brown, in one row; paraphyses colored. About seventy species. C. abietis (Pers.) Duby causes serious injury to pine. Ascoma dark-brown, erumpent, clustered ; spores eUipsoid, 10-12 x 5-7 II. Conidia ( = Brunchorstia destruens Erik.) in pycnidia which are partially embedded in the host, the smaller simple, the larger compound, 1-2 mm. in diam.; spores 30-40 x 3 m? tapering-rounded at each end, 2 to 5-septate. A second conidial phase ( = Dothichiza ferruginosa Sacc.) has simple spores. C. piniphilum Weir. Apothecia appearing singly, then in groups, rupturing the epi- dermis, coriaceous, membranaceous, 2-5 mm. across, carbonous; disc brownish to black, surface velvety or wrinkled; asci clavate, rounded above, long stipitate, averaging 135.8 x 14.1 ^x, 8-spored; spores irregularly 2-seriate, oblong to ellipsoid or fusiform, extrem- ities acute, hyaline, continous, averaging 18.9 x 6.4 /a; paraphyses filamentous, branched, longer than the asci, hyahne. On pine. The mycelium penetrates the cortex, phloem, and wood causing canker. Phacidiales (p. 94) This order, comprising some six hundred species only a few of which are pathogens, is characterized as follows: mycelium well developed, much branched, multiseptate ; ascocarps fleshy or leathery, free or sunken in the substratum or in a stroma, rounded or stellate, for a long time enclosed in a tough covering which at maturity becomes torn; paraphyses usually longer than the asci, much branched, forming an epithecium. 116 PLANT DISEASE FUNGI Phacidiaceae Apothecia sunken, more or less erumpent, disk-like or elongate, single or grouped, leathery or carbonous, black, firm, opening by lobes or rifts; hypothecium thin, poorly developed. Key to Genera of Phacidiaceae Apothecia firmly united to the substratum II. Phacidieae. Apothecia separate, no stroma Spores ellipsoid or globoid, 2 to 4-celled, brown 1. Keithia, p. 116. Spores fihform or needle-Hke, 1 to many- celled 2. Coccomyces, p. 117. Apothecia collected on a stroma, opening elon- gate, spores 1-celled, hyaline, filiform or needle-like 3. Rhytisma, p. 119. Keithia Saccardo Ascoma erumpent, disk black, asci 8-spored, paraphysate. Spores 1 -septate, ellipsoid-ovate, brown. K. thujina Dur. Ascoma epiphyllous, erumpent, at first buried beneath the epidermis which is lifted up, breaks around the margin, and finally falls away as an entire flap or scale, exposing the ascoma in the form of a cushion-like elevation. Ascoma circular to elongate- elliptic, straight or curved, convex above, 0.5 mm. broad, 1.25 mm. long: disk olive to olive-brown. Asci clavate, stout, 80-100 x 18- 20 M, opening by a pore. Spores 2, at first hyaline, finally olive- brown, broadly ellipsoid or piriform-ellipsoid, at first continuous, finally divided by a single transverse wall close to the distal end into very unequal cells, epispore with minute pits over its whole surface, 22-25 x 15-16 ju. Paraphyses branched below, septate, strongly clavate-thickened in the distal third, olive colored. The cause of black leaf spot of arbor-vitse. K. tsugae (Farl.) Dur. Ascomata hypophyllous, numerous, scattered, minute, at first buried beneath the epidermis which is finally ruptured and turned to one side as a scale, dark brown, orbicular to elliptic, 0.3-0.5 mm. in diameter. Asci oblong-clavate, apex rounded, 58-65 x 13-16 /x. Spores 4, uniseriate, at first hyaline, finally greenish-brown, ellip- PLANT DISEASE FUNGI 117 soid-ovoid, divided by one septum into two unequal cells of which the proximal is smaller, constricted at septum, 13-16 x 6-8 /x, smooth. Paraphyses cylindric, septate, hyahne below, the tips clavate, olive-brown, 4-5 ^ thick. On hemlock. Coccomyces DeNot (p. 116) C. hiemalis Higgins Ascocarps embedded in the tissue of the leaf, usually filling the entire space between the lower and the upper epidermis. Ovate to orbicular, dark brown or black. At maturity opening by irregular stellate slits on the under side of the leaves, 125-210 ix in diameter; asci 8- spored, 70-95 x 11-14 /x; paraphyses filiform, septate, apex slightly enlarged, often hooked or forked; ascospores linear, 33-50 x 3.5-4.5 /x, con- tinuous or 1 to 2-septate; apothecial conidia produced on short conidiophores in apothecia after shedding of ascospores, long, slender, 50-80 x 2.5-4 IX, curved, continuous or 1 to 2-septate. Conidial stage (=Cylindrosporium hiemalis): Fiq. in.— Cocco- Mycelium intercellular with small haustoria young haustoria in i«i J. J. i.v. i^ i. 11 r !_• leaf cells. After which penetrate the host cells; acervuli amphig- Higgins. enous, subepidermal, finally erumpent, exposing the spores; conidia elongate, curved or flexuous, 45-65 x 2.5-4 fx, continuous or 1 to 2-septate; microconidia (spermatia?) pro- duced in same acervulus in late summer and fall, small, continuous 4-5 x 1.55 ix. Conidial stage parasitic in leaves of Prunus avium, P. cerasus, and P. pennsylvanica. Ascig- erous stage saprophytic, appearing the last of April to June, on fallen leaves of the same hosts following the conidial stage. C. prunophorae. Higgins. Ascocarps hypoph- ^'?nV?u7u^TauTtoHa jHous, usually aggregated, subepidermal, erum- ioundeTry^cdiuiose P^^^' 125-250 X 100-160 fx, black, at maturity sheaths. After Hig- Opening in a stellate manner; asci 63-87 x 9- 12 /x; spores slender, straight, curved near the end, 40-60 x 2.5-3.5 At, continuous or 1 to 3-septate; paraphyses simple or branched, enlarged at apex, septate, apothecial conidia produced on short conidiophores inside the apothecia, following 118 PLANT DISEASE FUNGI the asci, usually 1-septate, 40-60 x 2.5-3.5 fx, resembling asco- spores, but usually stouter. Conidial stage ( = Cylindrosporium prunophorae) : Mycelium in- tercellular with haustoria which enter host cells; acervuli subepider- mal, amphigenous, finally breaking through exposing the white mass of spores, conidia elongate, slender, straight or curved, 46-65 x 3.5-5 /x, usually 1-septate; microconidia (spermatia?) found in same acervuli in late summer, small, continuous 4-5 x 1.5 /x. Conidial stage parasitic in leaves of plums, P. domestica, P. insititia, P. amer- icana and probably P. spinosa. Ascigerous stage saprophytic on fallen leaves of the same hosts. C. lutescens Higgins. Ascocarps hypoph- yllous, subepidermal, erumpent, 130-300 on Fig. 113. — Coccomyces w^^ _ . . . , Prunus, showing enlarge- X 70-150 /I, opcniug lu au irrcgular manner, ment of a layer of cells and • ■, , — ^ o/^ -^ a i r\ ^ their final separation causing aSCl ClavatC, 70-80 X 14-19 )U; SpOreS ClOU- Stir^H^'inl'^'''''"'^ ''''"'• gate, fascicled in end of ascus, 40-51 x 3.5- 4.5 /x, continuous or occasionally once or twice septate; paraphyses usually simple though occasionally branched, slightly enlarged at tip; apothecial conidia very long, 58- 87 X 3.5-5 /i, 1-septate with usually a single vacuole in each cell. Conidial stage ( = Cylin- drosporium lutescens) : My- celium intercellular, with haustoria which penetrate the host cells, acervuli subepi- dermal, amphigenous; conidia exuding in masses or in long tendrils from the break in the host epidermis, long, slender, 50-87 X 3.5-5 ^t, continuous, 1 to 3-septate, microconidia (spermatia?) produced in the same acervuli in late summer, small, continuous, 4-5 x 1 ;u. Conidial stage parasitic in leaves of P. serotina and in leaves and fruits of P. virginiana and P. mahaleb. Ascigerous stage saprophytic on fallen leaves of the same species. Fio. 114. — Coccomyces on Prunus. An acervulus showing the thin stromatic layer. After Hig- gins. PLANT DISEASE FUNGI 119 The three closely related species given above cause the ''shot holes" in leaves of the genus Prunus so long attributed to the species Cylindrosporium padi described by Karsten in 1884. The mycelium (on P. virginiana) is intercellular with haustoria which pene- trate the host cells; Fig. 112. The host cells are not killed at first and appar- ently die eventually from drying rather than from toxic action. The absciss layer causing the "shot holes'' is produced by the rapid enlarge- ment of a layer of cells at some distance from the ends of the mycelium. Fig. 113. The structure of the acervulus and of the ascocarp is shown in Figs. 114, 115. Positive inoculations have been secured both by conidia and by ascospores. C. pini (Alb. & Schw.) Karst.^ Ascocarp emergent, lacinate-dehiscent, disc. 1.5-4 mm. broad; asci long-pedicellate, 100-130 x 10-15 ai, 8-spored; spores filiform, clavate, 5 to 9-septate, 65-80 x 3^ /x; paraphyses filiform; conidial stage ( = Cylindrosporium sp) ; spores filiform, hyaline, continuous, 10 x 1 M. On white pine causing blight of the bark on twigs. Fig. 115. — An ascocarp of C hie- malis on its thick stroma. Af- ter Higgins. Rhytisma Fries (p. 116) To Rhytisma belong about 70 species which cause very conspic- uous, though but slightly injurious, black leaf spots. The spots, which are white within, are due to sclerotial cushions formed in the host tissue. Thickening of the leaf occurs in the infected part. One-celled conidia are abundantly produced in pycnidia early in the season, followed by sclerotium formation. Much later, usually well into winter or the following spring, the apothecia appear. Be- sides the ascospore-producing forms several species of which the ascospores are unknown have been referred here. Ascoma on a sclerotial stromatic layer, which is black above, white within; ascocarps elongate, opening by a lip-like slit; asci clavate, often blunt pointed, 8-spored; spores filiform or needle- 1 Graves, A. H. Notes on diseases of trees in the southern Appalachians. Phytop. 3: 129, 1913. 120 PLANT DISEASE FUNGI X «.' M. Fio. 116. — R. acerinum; conidial layer. After Tulasne. like, hyaline, mostly 1-celled, lyin^ parallel and lengthwise of the ascus; paraphyses filiform, hyaline, often arched above. R. acerinum (Pers.) Fr. The spot is at first yellow and thickened and in this stage bears numerous conidia upon short conidiophores. The apothecia ripen in spring and rupture by numerous irregular fissures which follow the ridges of the wrinkled surface. Klebahn secured infec- tion by ascospores resulting in three weeks in yellow spots and in eight weeks in conidiospores. The conidia are supposed to aid in spreading the fungus during the summer. Apothecia radiately 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 fx; paraphyses numerous, incurved or hooked. Conidia (=Melasmia acerina Lev.) preceding the asci, producing numerous, small, hyaline, 1-celled spores in an extended hymenial layer. On various species of maple, consisting of biologic races. R. punctatum (Pers.) Fr. also occurs on maple. It may be distinguished from the preceding by its small, speck-like stromata. R. salicinum (Pers.) Fr., found on willow, is quite fig. ii7. similar in external appearance to R. acerina. R. symmetricum Miill. is another willow inhabit- ing species. Hysteriales (p. 94) 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. Hypodermataceae Ascocarp flattened, rounded or elongate, rarely branched, im- mersed, united to the substratum; opening by a slit; asci 4 to 8- — Rhy- tisma. Ascus and paraphyses. After Rehm. PLANT DISEASE FUNGI 121 spored; paraphyses apically branched, the branches forming an epithecium, or hooked or crimped. Key to Geneka of Hypodermataceae Spores elongate, rather broad Spores 1-celled, hyaHne, asci 4-spored.. . 1. Hypodermella, p. 121. Spores 2-celled, hyaHne, apothecium black 2. Hypoderma, p. 121. Spores filiform, 1-celled 3. Lophodermium, p. 122. Hypodermella Tubeuf This differs from the next genus in its pyriform, unicellular spores; asci 4-spored. H. larius Tub. occurs on larch. Hypoderma De Candolle 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 is found on pine needles. r. n ff /^ W Amphigenous; asci broadly clavate, sessile; spores hya- line, linear-elliptic, obtuse and 2-rowed. H. laricis, and H. pinicola, produce premature leaf fall in various conifers. H. deformans Weir.^ Apothecia black, shiny, averaging 10 mm. in length and 1 mm. in breadth; open- ing with a longitudinal medial split. Asci fusiform, 8-spored, 26-43 X 159-207 /x. Spores parallel or obliquely arranged in the ascus, generally slightly curved, rod-shaped, ends blunt, 1 -septate when ma- ture, septum conspicuous, cells often apparently separated, pale ^ Weir, James R. Hypoderma deformans. An undescribed needle fungus of the western yellow pine. Jour. Agr. Res. 6: 277, 1916. Fig. 118. — Asci, spores, and paraphyses of Hypo- derma defermans. After Weir. 122 PLANT DISEASE FUNGI olive, almost hyaline, 6-10 x 90-131 m; paraphyses numerous, fila- mentous, swollen at the ends or recurved. Spermatia elongate, straight, sometimes slightly curved, hyaline, continuous, averag- ing 1 X 8 M- On pine needles causing their death. The fungus also reaches into the twigs causing hypertrophy and preventing proper develop- ment of the terminal shoots. Lophodermium Chevallier (p. 121) Spores long, thread-like, continuous; conidiospores in pycnidia. L. pinastri (Schr.) Chev. occurs on Pinus sylvestris especially on young plants causing the leaves to fall. The first year pycnidia only are formed, the asci not appearing until the second year. 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. Co- nidia cylindric, hyaline, continuous, 6-8 x 1 ;u. L. brachysporum Rost. = Hypoderma strobi- cola Tub. Perithecia epiphyllous; asci cylindric, short- stalked, apex rounded, 120 x 20-25 /jl; 8-spored; paraphyses bacillar, apex curved; spores oblong, 1-rowed, hyaline, 28-30 x 9-10 /x. It is common on pine leaves. Several other species are parasitic upon various conifers, among them: L. nervisequum (DC.) Fig. 119— L. pinastri. Fr. on fir Icavcs, causing defoliation and death; H, habit sketch; J, , • i i • i -ii tt i i • • ascus and paraphy- perhaps identical With Hypodcrma desmazieri see. After Rehm. -r-. i Aspergillales (p. 94) The Aspergillales are clearly distinguished from the other As- comycetes by the possession of a closed, astromate ascocarp, in which the asci are not collected in a hymenium but are irregularly scattered. The forms with the least developed peridium are ev- idently related to the Endomycetacese ; the forms with a more highly developed peridium, to the Pyrenomycetes, particularly to the Perisporiales. Conidial forms are usually present, indeed in many cases they preponderate almost to the entire exclusion of PLANT DISEASE FUNGI 123 the ascigerous form which may be seen only under very exceptional conditions. Sexual reproduction has been demonstrated in several families. In the Gymnoascacese there are usually two twisted branches which conjugate. These branches are multinucleate at the time of fusion. The ascogonium develops from this fertilization much as is described on pages 89, 90. In the Aspergillacese similar sexual organs are formed but parthenogenesis or a much reduced form of fertilization is often met. Aspergillaceae The ascocarp, in many forms but rarely seen, is a small spherical or tuber-shaped body, astromate, usually indehiscent, rarely open- ing by a pore. The spherical or pyriform asci bear from 2 to 8 spores which may be from 1 to many-celled. Conidia are produced in great abundance. In Aspergillus and Penicillium fertilization is accomplished by conjugation of a straight oogonium with a spirally coiled antherid- ium, this act resulting in an ascogenous hypha. A reduced form of sexuality consisting of fusion of the nuclei of the ascogonium with each other probably also occurs. Key to Genera of Aspergillaceae Spores 1-celled, perithecium not beaked, un- appendaged; peridium membranous or fleshy Conidia borne directly on the mycelium; chlamydospores borne in chains 1. Thielavia, p. 123. Conidia borne on distinct conidiophores in chains Conidiophores enlarged apically bearing nu- merous sterigmata 2. Aspergillus p. 124. Conidiophores bushy branched, single; peri- thecia sessile 3. Penicillium p. 125. Thielavia Zopf T. basicola (B. & Br.) Zopf This, the one species of the genus, is on the boundary between the Aspergillales and the Perisporiales and is classed by some with the one, by some with the other order. The ascocarps, which are the form less commonly seen, are 124 PLANT DISEASE FUNGI round, brown, completely closed and have no appendages. The asexual spores are of two kinds. First: hyaline conidia produced endogenously within '' pistol-formed" conidiophores from the ends of which they are expelled. Second: short cylindrical co- nidia or chlamydospores with a thick brown wall; borne in series of three to six on the ends of hyaline branches. Fig. 120. These conidia fall apart as they age. The hyaline conidia pre- ponderate in early disease, giving the surface of the root a mildewed appearance ; the dark conidia preponder- ate later, covering the root with a black coating. Fi- nally, after the host is dead, the ascocarps appear. Very young seedlings may be killed. Older plants are 17 ,or. ^ u • 1 u • . • ,• , . invaded onlv in the roots, I-IG. 120. — r. basicola, snowing two comdial forms . " , , , i and ascus and ascospores. After Van Hook and the rOOt tlSSUe bemg brO\Vned and killed. The delicate hyaline mycelium wanders through the affected root disorganizing its tissue. The superficial mycelium is lightly tinted. Perithecia 80-100 /jl; asci ovate, 8-spored; spores lenticular, vacuolate, 1-celled, chocolate-colored, 8-12 x 4-5 fx; chlamydo- spores in chains, at maturity separating, short-cylindric, about 5-8 x 12 jLt; the entire group 25-65 ^ long; conidia hyaline, about 10-20 X 4-5 M. It primarily attacks legumes, cucurbits and the Solanacese, but is known in fifteen other families on nearly 100 hosts, among them Aralia, Begonia, Catalpa, Cyclamen, cotton, Linaria, Lupinus, Nas- turtium, tobacco, bean, pea, sweet pea, clover, ginseng, cowpea, violet. Aspergillus Micheli (p. 123) The ascocarps are small, spherical, indehiscent, smooth bodies which at maturity are entirely filled with 8-spored asci; spores PLANT DISEASE FUNGI 125 1 -celled. The conidiophores, which serve better to characterize the genus, are swollen at the end, and bear numerous sterigmata on which the spores are borne basipetally in chains. (See p. 380.) Penicillium Link (p. 123) The ascocarp is much as in the last genus, with the asci 4 to 8-spored. It may develop directly from the mycelium or with the intervention of a sclerotial stage. The characteristic conidiophore serves to distinguish the genus by its mode of branching. Fig. 347. Instead of being apically swollen as in the preceding genus it branches repeatedly, the branches bearing terminal sterigmata and giving the conidiophore the appearance of a brush; hence the name. For species see page 381. Myriangiales ^ (p. 94) Ascocarp stromatic, superficial, immersed or erumpent; asci irregularly disposed. PlectodiscelleaB Ascocarp innate, indefinite; stroma colorless, prosenchymatic, with a dark, clypeus-like cover. Plectodiscella Woronin Spores colorless, transversely 4-celled. P. veneta Burk. Ascocarp pulvinate, minute (75 /x) , brown to black, scattered or grouped, stromatic. Asci globose, thick-walled, 24-30 ji in diam- eter, 8-spored, scattered irregularly in the stroma. Spores ovate, 4-celled, 18-21 x 6-8 /x, hyaline, constricted at the septa. Conidial stage (=Gloeosporium venetum Speg.) caulicolous or foliicolous; spots orbicular or elliptic, border raised, darker, 2-3 mm. in diameter; conidia in acervuli on short, simple conidiophores, continuous, oblong, elliptic, 5-7 x 3 /z, in mass amber-colored. The fungus occurs on all aerial parts of the raspberry causing serious disease. It was first reported in Italy in 1879. On canes small purple spots first show near the ground, enlarge and soon develop ashen centers. The leaf spots are small, often scarcely 1 mm. in diameter. ^ Theissen and Sydow, Syn. Taf . 1. c. 126 PLANT DISEASE FUNGI The ascocarps appear in August and the asci mature, usually, in the following spring, the spores being liberated by disintegra- tion of the overlying stromatic tissue. Hibernation is chiefly as Fig. 121. — P. veneta, ascocarp showing arrangement of the asci in the stroma, After Burkholder. mycelium within the canes. On canes infection results in death and collapse of the epidermal and cortical cells accompanied by hyperplasia of the parenchyma and phloem. Abnormal growth tensions develop leading to fissures. Myriangiaceae Perithecia erumpent, free, definitely formed. Stroma not slimy incrusted. Interascicular stroma cellular, not paraphysate; asci in several series. Myriangium Mont. & Berk. Ascigerous region locally limited from a sterile basal stroma, spores hyaline, muriform; no free mycelium. A species has been reported on the pecan. Pyrenomycetes The following five orders are usually grouped together as the Pyrenomycetes; separated from the preceding forms by their closed ascocarp with the asci arranged in a hymenium. They constitute a vast assemblage of more than ten thousand species, the large PLANT DISEASE FUNGI 127 majority saprophytic and unimportant except in the general economy as scavengers. Perisporiales (p. 94) The present order is characterized by its almost universally par- asitic habit, the evident mycelium and the globoid perithecia with- out ostioles. The mycelium is superficial upon the host and fre- quently quite conspicuous. Key to Families of Perisporiales Mycelium white; perithecia with appendages. . 1. Erysiphaceae p. 127. External mycelium dark colored or wanting Mycelium not slimy, straight- walled ; peri- thecium not slimy 2. Perisporiaceae, p. 142. Mycelium dematioid or straight-walled, but then slimy 3. Capnodiaceae, p. 144. Erysiphaceae ^ ,2,3 This family on account of its abundance everywhere, its sim- plicity of structure, and its possession of typical ascigerous and conidial stages forms a favor- ite type for introductory study of the Ascomycetes. Its members are easy of rec- ognition, forming a coating of white conidia, conidiophores and mycelium upon the sur- face of its hosts and giving them an appearance much as though they had been lightly dusted with flour. Later in the season the white patches are more or less liberally sprinkled with the black peri- thecia leading to the common name powdery mildew. The mycelium except in Phyllactinia is entirely superficial. It is usually quite hyaline and is branched, septate and its cells uni- 1 Salmon, E. S. Monograph of the Erysiphaceae. Mem. Torr. Bot. CI. 9: 1900. 2 Halstead, B. D. N. J. Agr. Exp. Sta. Rept. 24: 517-536, 1903. ^ Reed, G. M. The powdery mildews. Erysiphacese. Trans. Amer. Micr. Soc. 32: 219, 1913. Fig. 122. — I, E. graminis, showing branching hau3- toria. .3.3, Phyllactinia, intercellular hyphse. After Smith. 128 PLANT DISEASE FUNGI nucleate. It fastens to the host and penetrates its epidermal cells by uninucleate haustoria which by their various lobings aid in specific characterization. Figs. 122, 123. Haustoria may be grouped in three general classes; (1) those arising directly from the lower surface of the mycelium; (2) those arising at the side of the mycelium as small semicircular processes ; (3) arising from more or less deeply-lobed lateral swellings of the mycelium. The conidia arise in basipetal succession on simple, scattered conidiophores (Fig. 129); are hyaline, oval or barrel-shaped, smooth, 1 -celled. They vary greatly in size with nutrition con- ditions. Conidia germinate readily at once in dry air, better in humid air, producing from one to three germ tubes. Haustoria are formed at once and the mycelium develops to a more or less cir- cular colony, producing new conidia in a few days. Artificial in- oculations on susceptible plants, using conidia, usually result within two to five days in typical mildew spots. Neger who studied the germination of conidia extensively has shown that light hastens the growth of the germ tubes, which in many cases are negatively phototropic. Con- tact stimulus leads to the growth of ap- pressoria. The perithecia are subspherical, often some- what flattened, white to yellow when young. Fig. 123.— Erysiphe, show- dark to black and reticulated when mature; ief sai'mon^''"'^''"^* ^^' are without ostiole but are provided with ap- pendages of various types. Figs. 130, 131, 134, which give main characters to mark the genera. The append- ages serve by hygroscopic movements to aid in the distribution of the fungus. The ascospores become free after dissolution of the perithecium by weathering. The asci are either solitary or quite numerous within the perithecium and bear two to eight hyaline spores each. The conidia are short-lived, summer spores. The perithecia mature more slowly and constitute the hibernating condition. In some instances the ascus-f orm is unknown ; the fungus is then clas- sified solely by its conidial stage and falls under the form genus Oidium (see p. 379). In Sphserotheca an antheridial and an oogonial branch, each uninucleate, are developed, and cut off by septa. The oogonium PLANT DISEASE FUNGI 129 124. — Ascogonium- tube with five nuclei. Af- ter Harper. enlarges; the antheridium lengthens, its nucleus divides, and a septum is run in separating the stalk cell from the antheridium. The sperm nucleus enters the oogonium and fuses with the oogonial nucleus. Simultaneous with fertilization occurs, from the stalk cell of the oogonium, the development of a sterile sj^stem of envel- oping threads which surround and protect the fertilized oogonium and eventually mature into the perithecial wall. The fertilized oogonium divides several times transversely producing a series of cells, one of which is binucleate. This binucleate cell after fusion of its nuclei develops into the one ascus, char- acteristic of the genus. The ascus nucleus by division gives rise to the spore nuclei and the fig spores are cut out of the periplasm by re- flexion of the astral rays. In Erysiphe the oogonium and antheridium arise in a very similar way, the oogonium being somewhat curved. Fertilization is also similar consisting of the union of two gametic nuclei. After fertilization the oospore nucleus divides and the oogonium de- velops into a short bent tube, which contains from five to eight nuclei. Septa now appear cutting off cells, some uninucleate, some with two or more nuclei. The ascogenous hyphse develop a knot and soon divide into two or three cells each and give rise to the asci which are in the be- ginning binucleate. In Phyllactinia the oogonium, antheridium and fertilizations are as in Erysiphe, though the oogonium may be quite curved TT 10- TDv, 11 ^- • 1 ^ f , so as to make almost a com- FiG. 12o. — Phyllactinia, male and femala branches; uninucleate oogonium and anther- pletc tum arOUud the anther- idium. After Harper. . ,. -r-,. -,^_ idmm. Fig. 125. After fertilization the antheridium degenerates and enveloping protective hyphse arise both from the oogonium and the anther- idium stalk cells. The oogonium becomes three to five nucleate and develops to a row of cells of which the penultimate cell has more than one nucleus. The ascigerous hypha) arise from this binu- cleate cell, perhaps also from other cells of the series, become septate and form the asci either terminally, laterally or inter- 130 PLANT DISEASE FUNGI calary. The young ascus is binucleate, fusion follows and the spores develop as in the preceding genera. The family contains, according to Salmon, forty-nine species and eleven varieties; according to Saccardo more than one hun- dred species. These are parasitic on some one thousand five hun- dred hosts, some of them upon economic plants and of marked harmfulness. The matter of delimiting species and even genera is often diffi- cult, owing to intergrading forms. This question is complicated still further by biologic specialization, such that forms, which are indistinguishable under the microscope, show in inoculation tests different abilities regarding host infection. Thus Neger, Salmon, Reed, and others have shown that spores borne on a particular host are capable of infecting only that host or in other cases only nearly related species of the same host genus. Forms which can pass from one genus to another are less common. Forms morpho- logically distinct are regarded as separate species. Differentia- tions within such species, regarding the species of host plant which they parasitize, give rise to '' biologic species" or ''biologic varieties." Reed writes of these biologic forms thus: "So far as investigated, Erysiphe cichoracearum, is the only one with doubtful exceptions, . . . shown to be capable of in- fecting plants belonging to more than one genus." "There are other cases where the mildew is limited closely to plants of a single genus," and "Several cases are recorded where the mildew from one species will not infect other species of the same genus. Most of these claims, however, rest on insufficient data." Some morphological species show a very wide range of hosts; one species, Phyllactinia corylea is known on forty-eight genera in twenty-seven families, others are limited to single genera or to single species of host plant. Two, three, and even five species are recorded for some species of host. Geographically the Erysiphacese are widely distributed, prac- tically of world distribution, but they are more abundant in the temperate zones than elsewhere. A pycnidium-bearing parasite, Cicinnobolus is quite frequently found on the mycelium and conidiophores of the Erysiphaceae. Owing to the extreme variability of the perithecial characters this family presents a most difficult problem to the taxonomist who must either segregate or "lump" species. No middle ground seems open at present. PLANT DISEASE FUNGI 131 Key to Subfamilies and Genera of Erysiphaceae Mycelium wholly external to the tissues of the host plant, usually sending haustoria into the epidermal cells only, perithecial appendages various, more or less flaccid I. Erysipheae. Perithecial appendages indeterminate, similar to the mycelium, simple or ir- regularly branched Perithecia containing a single ascus. ... 1. Sphserotheca, p. 131. Perithecia containing several asci 2. Erysiphe, p. 133. Perithecial appendages determinate Appendages hooked or coiled at the apex 3. Uncinula, p. 136. Appendages dichotomous at the apex Perithecia containing a single ascus ... 4. Podosphaera, p. 137. Perithecia containing several asci .... 5. Microsphaera, p. 139. Mj^celium with special intercellular haus- toria-bearing branches which enter the host by the stomata; perithecial ap- pendages rigid, with a bulbous base. ... II. Phyllactinieae. A single genus 6. Phyllactinia, p. 141. Sphaerotheca, Leveille Perithecia subglobose; appendages floccose, brown or hyaline, spreading horizontally and often interwoven with the mycelium, simple or vaguely branched, frequently obsolete; ascus single, 8-spored. Five species, according to Salmon; Lindau gives four- teen. S. humuli (DC.) Burr. Amphigenous; mycelium usually evanescent; perithecia usually somewhat gregarious, but varying from scattered to cespitose, 58-120 M in diameter; cells small, averaging 15 /x; appendages few or numerous, usually long, often exceeding nine times the diameter of the perithecium, more or less straight, septate, dark brown throughout: variations are; short, flexuose, pearly-brown, white or even obsolete. Ascus broadly-elliptic to subglobose, rarely abruptly stalked, 45-90 x 50-72 /i; spores 20-25 x 12-18 fx, rarely larger, averaging 22 x 15 ijl. Conidia ( = Oidium fragarise) ovate, white, membrane smooth. Subjecting the conidia of this variety to low temperature, 0° two hours, increases their germinating power. 132 PLANT DISEASE FUNGI The species is cosmopolitan and among its numerous hosts are the economic genera Dipsacus, Fragaria, Humulus, Phlox, Pyrus, Rosa, Ribes, Rubus, Scabiosa, Spirea and Viola. A degree of host specialization exists. It is a common rose mildew and is also destructive on the straw- berry. S. humuli var. fuliginea (Schl.) Salm. Perithecia usuall}^ smaller than in the last, sometimes only 50 m in diameter, wall usually harder and more brittle, cells larger, ir- regularly shaped, averaging 25 fi; appendages usually short, pale brown; spores 20-25 x 12-15 m- It is recorded on Arnica, Calendula, Coreopsis, Fragaria, Gail- lardia, Impatiens, Phlox, Scabiosa, Taraxacum, Verbena, Viola. S. pannosa (Wallr.) Lev. Mycelium persistent, forming dense satiny patches on the stem, calyx, petiole, and rarely on leaves, at first shiny white, then becoming gray, buff or rarely brown; perithecia more or less, usually completely, immersed in the persistent mycelium, glo- bose to pyriform, 85-120 // in diameter, usually about 100 n, cells obscure, about 10 /jl wide; appendages few, often obsolete, very short, tortuous, pale brown, septate; ascus broadly-oblong to globose, 88-115 fx, averaging 100 x 60-75 m; spores 20-27 x 12-15 m- Conidia (= Oidium leucoco- nium) ovoid, 20-30 x 13-16 fi, hyaline; conidiophores short. Hosts: peach and rose. The conidia are very common on the rose, but the perithecia are rare. What often passes for this species on roses in America is in reahty S. humili. S. mors-uvae (Schw.) B. & C. The mycelium at first white, is exceptional among the Erysiphese in that it later becomes quite brown. It is found in closely felted patches on stems and fruit. Perithecia begin to form in June. Amphigenous; mycelium persistent, at maturity forming dense pannose patches of brownish hyphae; perithecia gregarious, more Fig. 126. — S. mors-uvae, a perithecium dis- charging its single ascus which contains eight spores. After Longyear. PLANT DISEASE FUNGI 133 or less immersed in the persistent mycelium, subglobose, 76-110 ju in diameter; cells large, at first well defined, then becoming obscure, 10-25 ix wide; appendages usually few or even obsolete, pale-brown, short, rarely longer, up to five times the diameter of the perithecium, tortuous; ascus elliptic-oblong to subglobose, 70-92, rarely 100 x 50-62 m; spores 20-25 x 12-15 m- On wild and cultivated species of Ribes in America; whence it was introduced into Europe where it is very destructive. S. lanestris Hark, occurs on various species of oaks. Erysiphe Hedwig (p. 131) Perithecia globose, or slightly depressed, rarely concave; ap- pendages floccose, simple or irregularly branched, sometimes obsolete, usuallj^ more or less similar to the mycelium and inter- woven with it; asci several, 2 to 8-spored. Salmon recognizes eight species; Lindau, twenty. E. polygoni DC. Amphigenous; mycelium very variable, persistent, thin, effused and arachnoid, rarely thick, or more often evanescent; perithecia gregarious or scattered, usually rather small, averaging 90 /*, but ranging from 65 to 180 ^i; cells usually distinct, 10-15 /u wide; appendages very variable in number and length, few or many, distinct or more or less interwoven with the mycelium, brown or colorless; asci 2-8 or rarely as many as 22, variable in shape and size, usually small and ovate, with or without a short stalk, 46-72 ^ig. 127.— e. poiy X 30-45 At; spores 3-8 rarely 2, 19-25 x 9-14 11. ^^^ a^d. After Sai- Conidiophores (=Oidium balsamii). Destructive to the pea and turnip. It was studied by Salmon on one hundred ninet}^ host species belonging to eight3^-nine genera; one hundred forty-six more hosts, some doubtful, are reported. Among the economic host genera are Adonis, Alyssum, Anemone, Aquilegia, Brassica, Calendula, Catalpa, Clematis, Cucumis (?), Cucurbita (?), Dahlia, Daucus, Delphinium, Dier- yilla, Dipsacus, Fagopyrum, Lupinus, Lycopersicum, Medicago, Pseonia, Phaseolus, Pisum, Tragopogon, Trifolium, Verbena, Vicia, Vigna (cowpea) Scabiosa, Symphytum, Valeriana. This is the most variable species of this genus, varying widely in its every character. It includes several species which have by 134 PLANT DISEASE FUNGI some been set aside as distinct, e. g., E. martii, E. umbelliferarum and E. liriodendri. Salmon found that the conidia of this form grown on Trifolium pratense were unable to infect other species of Trifolium. E. cichoracearum DC. Amphigenous; mycelium usually evanescent, rarely persistent, white or sometimes pink; perithecia gregarious or scattered, 80- 140 or rarely 180 /jl; cells variable, often very distinct, 10-20 n; appendages variable in numl3er and size, some shade of brown; asci usually numerous, about 10- 15, but varying from 4 to 36, variable in size and shape, nar- rowly ovate or subcylindric to broadly-ovate, more or less stalked, 58-90 X 30-35 /x; spores 2, rarely 3, 20-28 X 12-20 jjl. Conidiophores (= Oidium am- brosise Thiim), short; conidia mi- nute, elliptic, white, 4-5 x 2.5-3 fi. The species is quite variable, sometimes closely approaching E. polygoni. The hosts are very numerous, among them being: Calendula, Centaurea, Cichorium, Clematis, Fig. 128.— E. cichoracearum, asci and CuCUrbita, Dahlia, HelianthuS, spores. After Salmon. -rr ^ -i\ /r j i -nt* j- Humulus, Mentha, JNicotiana, Phlox, Tragopogon, Valeriana, Verbena, Symphytum. It is of especial import on composites and cucurbits. Reed has made very extensive culture studies of this species and concludes that the same form of "Erysiphe cichoracearum DC, occurs on at least eleven species of the cucurbits, belonging to seven genera, infection occurring in these cases in fifty per cent or more of the trials. Six other species were also infected, but in a smaller percentage of cases. ... It is also plain that the biologic form of Erysiphe cichoracearum, occurring on so many cucurbits is not entirely confined to the species of this one family. Out of fifty-four leaves of Plantago rugelii, a species belonging to the Plantaginacese, which were inoculated, ten became infected. . . . Furthermore out of ten leaves of squash seedlings, inoculated with conidia from plantain, six became infected . . . and the sunflower, PLANT DISEASE FUNGI 135 Helianthus ami mis, was infected in thirty-five per cent of the trials in which conidia from the squash were sown on leaves of seedlings. . . . The cucurbit mildew could not be transferred to asters and goldenrods nor was the mildew occurring on these in nature able to infect the squash. Neither the aster mildew nor the cucurbit mildew proved able to infect a goldenrod, Solidago csesia. Nor was the mildew on this host able to infect asters or squashes." E. graminis DC. Usually epiphyllous, rarely amphigenous; mycelium more or less persistent, forming scattered patches, at first white, then brown or gray; perithecia large, 135-280 m, usually about 200 ju, scattered or gregarious, cells ob- scure; appendages rudimentary, few or numer- ous, very short, pale brown; asci numerous, 9- 30, cylindric to ovate-oblong, more or less long- pedicellate, 70-108 X 25-40 //; spores 8, rarely 4, 20-23 X 10-13 fjL, seldom produced on the living plant. Conidial form(=Oidium monilioicles) with a grayish cast; conidiophores medium tall; conidia ovoid, white or sordid, 25-30 x 8-10 fj,. It is found on a large number of species of the Graminese including species of Avena, Fes- tuca, Hordeum, Phleum, Poa, Saccharum, Secale, and Triticum. The asci are peculiar in that they usually con- tain undifferentiated granular protoplasm, not spores, though in some cases the spores, normally 8, are present. This species on grasses shows no morphologi- cal differences, vet inoculation tests have re- vealed in it numerous biologic varieties. Reed summarizes the results of his own work together with that of Marchal and Salmon as follows : ''So far as tested, all species of Avena are susceptible to the oat mildew. All species of Triticum are likewise susceptible to the wheat mildew. We find, however, that certain varieties of Triticum dicoccum are prac- tically immune to the wheat mildew. Other varieties of this same species are entirely susceptible. Some species of Hordeum are immune to the barley mildews, and the same seems to Fig. 129.— E. gram- inis, conidial stage. After Salmon. 136 PLANT DISEASE FUNGI be true of certain species of Secale with reference to the rye mildew. "To these general statements there are two possible exceptions. Marchal states that the oat mildew will infect Arrhenatherum elatius. Salmon, however, obtained a negative result with the oat mildew on this grass. The evidence is not conclusive either way. The other exception is that, according to Salmon, conidia from wheat can infect Hordeum silvaticum. "It would seem then that under normal conditions there are well-defined forms of Erysiphe graminis occurring respectively on the species of each of the four cereals." It is thought that some hosts may act as bridging species and enable the parasite to pass from one host to another to which it could not pass directly. Uncinula Leveille (p. 131) Perithecia globose to globose-depressed; appendages simple or rarely once or twice dichotomously forked, uncinate at the apex, usually colorless, rarely dark brown at base or throughout; asci several, 2 to 8-spored. There are eighteen or twenty species. U. necator (Schw.) Burr. Amphigenous ; mycelium subpersistent ; perithecia usually epiph- yllous, occasionally hypophyllous or on the inflorescence, more or less scattered, 70-128 m; cells distinct, rather irregular in shape, 10-20 m; appendages very variable in number and length, 7-32, rarely up to 40, 1 to 4-times the diameter of the perithecium, sep- tate, thin walled, light or dark amber-brown basally, rarely branched, asci 4-6 rarely up to 9, broadly-ovate or ovate-oblong to subglobose, with or without a short stalk, 50-60 x 30-40 jjl; spores 4-7, 18-25 x 10-12 fi. Conidial form ( = Oidium tuckeri) , conidiophores short ; conidia elliptic, oblong, or obtusely rounded, 2 to 3-catenulate, hyaline, 25-30 X 15-17 M- Hosts: Vitis, Ampelopsis and Actinidia. This species is one of the worst pests of the family. The mycelium is thin walled and sparingly septate. The haus- toria arise from lobed lateral swellings of the hyphse, penetrate the epidermis with a filamentous projection and swell within the host cell to a bladder-like body. The parasitized cells and later the neighboring ones turn brown and die. PLANT DISEASE FUNGI 137 The conidia germinate readily in moist air or in water, sending forth from one to several germ tubes. The perithecia are found well developed as early as June or July in the United States and are rather evenly scattered over the affected surfaces. A period of warm moist weather which favors luxuriant mycelial growth, followed by sudden low- ering of temperature to about 50° F., fa- vors their most rapid formation. They are at first hyaline, later brown. After their form and walls become definite, usually during winter, the appendages (g- develop as outgrowths from the outer walls. During winter the appendages break off. Galloway failed to secure ger- mination of ascospores earlier than Feb- ruary or March, but perithecia which had been exposed to the weather until spring and were then placed in a hanging drop culture afforded spores, some of which grew though many of them burst as they emerged from the perithecium. Asco- ^^^: i3o.— u necator ii. Peri- ^ *^ •I'll thecium snowing /, append- spores are known to have remained viable ages, and a, asci. iv. Group • of SiSci rGmovGQ from pGrithc- for at least eighteen months. No success- dum emitting s, ascospores. /. 1 • /. . • 1 r After Viali. lul imections were made irom ascospores. Though perithecia are frequently found in America they were not found in Europe until 1892 and are now found there but rarely. It appears that in their absence the fungus hibernates in specially resistant cells of the mycelium which develop within knotty swell- ings near the haustoria. Other species are U. salicis (DC.) Wint. on willow and poplar, U. aceris (DC). Sacc. and U. circinata C. &. P. on maple, U. flexuosa Pk. on ^sculus, and elm, U. clandestina (Biv.) Schr. on elm, U. prunastri (DC.) Sacc. on Prunus. Podosphsera Kunze (p. 131) Perithecia globose or globose-depressed; ascus solitary, sub- globose, 8-spored; appendages equatorial or apical, dark-brown or colorless, dichotomously branched at the apex, branches simple and straight or swollen and knob-shaped; appendages rarely of 138 PLANT DISEASE FUNGI two kinds, one set apical, brown, rigid, unbranched or rarely 1 to 2-times dichotomous at the apex, the other set basal, short, flexuous, frequently .obsolete. Salmon recognizes four species; Lindau seven. P. oxyacanthae (DC.) de Bary Amphigenous; mycelium variable, persistent in thin patches or evanescent; perithecia scattered or more or less gregarious, subglobose, 64-90 ju; cells 10-18 ;u; appendages spreading more or less, equatorial, variable in number and length, from 4-30 in number and from 3^-6 or even 10- times the diameter of the perithecium, usually unequal in length, dark brown for more than half their length from the base, apex 2 to 4- times dichotomously branched, branches usually ^^?hi,^app«iS^t5S' short and equal, ultimate branches rounded. After Salmon. swollcu, and more or less knob-shaped. Fig. 131, ascus broadly obovate, or subglobose, 58-90 x 45-75 /x; spores 8, rarely 6, 18-30 x 10-17 ix. Conidia ( = Oidium cratsegi) . On some hosts perithecia are rare. It is thought that the my- celium remains alive over winter. Hosts: Amelanchier, Crataegus, Diospyros, Prunus, Pyrus, Spirea and Vaccinium. Especially damaging to cherry and apple. Throughout the northern hemisphere. P. tridactyla (Wallr.) de Bary is considered by Salmon as a variety of the last species. Hosts: Plum and other species of Prunus and of Spirea. Similar to the preceding in habit and general character but differing in more critical characters. Perithecia 70-105 ju; cells 10-15 ix] appendages 2-8 usually 4, 1 to 8-times the diameter of the perithecium, apical in origin, more or less erect, apically 3-5 or 6-times dichotomously branched, primary branches usually more or less elongate, sometimes slightly recurved; asci globose or subglobose, 60-78 x 60-70 m; spores 8, 20-30 x 13-15 ix. P. leucotricha (E. & E.) Salm. Mycelium amphigenous, persistent, thin, effused; perithecia densely gregarious, rarely more or less scattered, 75-96 ^, sub- globose, cells 10-16 /z; appendages of two kinds, one set apical the other basal; apical appendages 3-11 in number, more or less widely spreading, or erect-fasciculate, 4 to 7-times the diameter of the perithecium, apex undivided and blunt or rarely once or PLANT DISEASE FUNGI 139 twice dichotomously branched, brown basally; basal appendages nearly obsolete or well developed, short, tortuous, pale brown, simple or irregularly branched; ascus oblong to subglobose, 55-70 X 44-50 /i, spores 22-26 x 12-14 n, crowded in the ascus. Conidia (=Oidium farinosum): elhpsoid, trun- cate, hyahne, 28-30 x 12 ^x. This and P. oxyacanthse, the apple mildews of America, have been variously treated by writers so that the literature presents an almost inextric- able tangle, Podosphsera oxyacanthse being fre- quently reported instead of P. leucotricha. Sphse- rotheca mali and Podosphaera oxyacanthse have also been much confused, due to similarity of habit and the frequent abnormal development of the appendages, so that the published references are not always reliable. Though invasion is only into the epidermis by haustoria the infected leaves are stunted, the internodes shortened; also twigs may be thickened. It has been demonstrated that the mycelium passes the winter in a dormant condition within buds and as these open in the spring growth resumes. Fig. 132.— p. leuco- tricha, appendage tips. After Sal- mon. Microsphaera Levielle (p. 131) Perithecia globose to subglobose; asci several, 2 to 8-spored appendages not interwoven with the mycelium, branched in a definite manner at the apex, usually dichotomously and often very ornately, rarely undivided or merely once dichotomous. According to Salmon there are thirteen species; Lindau recognizes thirty. M. grossulariae (Wallr.) Salmon Epiphyllous or amphigenous; mycelium evanescent or subper- or densely aggregated, globose- depressed, 65-130 n] cells 14-20 /i; appendages 5-22, colorless, 1-1 J^ times the diameter of the perithecium, 4 to 5-times closely dichotomously branched, branches of first and second order very short, all segments deeply divided, tips not recurved; asci 4-10, Fig. 133. — M. grossularise appendage tips After Salmon. sistent; perithecia scattered 140 PLANT DISEASE FUNGI broadly ovate or oblonj>;, usually with a very short stalk, 46-62 X 28-38 m; spores 4-6, rarely 3, 20-28 x 12-16 fi. On five species of Ribes and two of Sambucus. This is the European gooseberry-mildew, common on America only on the elder. M. alni (Wallr.) Lev. Amphigenous; mycelium evanescent or persistent; perithecia scattered to gregarious, globose-depressed, very variable in size, usually small, 66-110 jjl, or even up to 135 fj,; cells 10-15 /x wide; appendages variable in number (4-26) and length, Ys to 23/^ times the diameter of the perithecium, more or less rigid, color- less throughout or amber-brown at base, apex variously, but not always, more or less closely 3 to 6-times dichotomously branched, tips of ultimate branches regularly and distinctly recurved; asci 3-8, ovate to ovate-globose, 42-70 x 32- 50 fjL, usually but not always short stalked; 4 to 8-spored; spores 18-23 x 10-12 M- This species is the most variable of the Erysiphese showing large latitude in number of spores in the ascus, in length, F.o. i34.-M.^^aim^^apjjendage tips. ^^j^^. ^^^ branching of appendages, in size of perithecia. It occurs upon very numerous hosts. The economic ones on which it is most common are: Syringa, Lonicera, Alnus, Betula, Quercus, Carya, Pecan, Castanea, Juglans, Platanus, Sweet pea. It is confined to the northern hemisphere. Salmon recognizes in addition to the typical form six va- rieties. M, diffusa C. & P. Amphigenous; mycelium persistent, thin and effused, or sub- persistent and forming vague patches, or quite evanescent; peri- thecia scattered or gregarious, globose-depressed, very variable in size, 55-126 fx in diameter, averaging 90-100 fi, cells 10-20 /x wide; appendages very variable in number and length, 4-30, or rarely crowded and as many as 50, 13^ to 7-times the diameter of the perithecium, smooth, aseptate or 1 to 3-septate in the lower half, colorless or pale brown towards the base, flaccid when long, thin-walled above, becoming thick-walled towards the base, apex 3 to 5-times dichotomously or subdichotomously divided, branch- ing diffuse and irregular, branches of the higher orders sub-nod- PLANT DISEASE FUNGI 141 ulose, often apparently lateral, tips of ultimate branches not recurved; asci 4-9, 48-60 x 28-30 fx, ovate-oblong with a very short stalk; spores 3-6, usually 4, 18-22 x 9-1 l^t. Hosts; Desmodium, Glycyrrhiza, Lespedeza, Phaseolus, Sjon- phoricarpus. M. euphorbiae (Pk.) B. & C. occurs on various hosts including Astragalus, Colutea, Cuphea and Euphorbia. Its only economic importance is as the cause of a disease of the roselle and cowpea on which it is very common. Amphigenous; mycelium usually subgeniculate; perithecia gregarious in floccose patches or scattered, 85-145 /z, rarely 180 /i, cells 10-15 ix] appetidages 7-28, usually narrow, more or less flexuose and nodose, 2.5 to 8-times the diameter of the perithecium, colorless above, 3 to 4-times dichotomously branched, branching, irregular and lax, asci 4-13, rarely up to 26, ovate or ovate-oblong, short-stalked, 48-66 x 26-35 ix; spores usually 4, rarely 3, 5 or 6, 16-21 X 10-12 11. Phyllactinia Leveille (p. 131) Perithecia large, globose-depressed to lenticular; asci many, 2 or 3-spored; appendages equatorial, rigid, acicular, with a bul- bous base; apex of perithecium with a mass of densely crowded branched outgrowths. Typical epidermal haustoria are not produced but the mycelium sends special branches through the stomata into the intercellular spaces of the leaf. These branches attain some length and con- stitute a limited internal mycelium, a character that is considered by some as of sufficient importance to set the genus apart in a separate family. The internal mycelium gives off haustoria which penetrate cells of the mesophyll. The appendages exhibit striking hygroscopic movements and aid in dissemination. Only one species is recognized by Salmon. P. corylea (Pers.) Karst. Hypophyllous or rarely amphigenous; mycelium evanescent or more or less persistent; perithecia usually scattered, rarely gregarious, 140-270 /z, rarely up to 350 /x; cells rather obscure, 15-20 II) the apical outgrowth becomes mucilaginous attaching the perithecium firmly to places where it may fall; appendages 5-18, equatorial, 1 to 3-times the diameter of the perithecium; asci 5^5, subcylindric to ovate-oblong, 60-105 x 25-40 /z, more or less stalked, 2, rarely 3-spored; spores 30-42 x 16-25 /x. 142 PLANT DISEASE FUNGI Conidia ( =Ovulariopsis), acrogenous, solitary, hyaline, sub- clavate. On Magnolia, Liriodendron, Berberis, Xanthoxylum, Ilex, Celas- trus, Acer, Desmodium, Crataegus, Heuchera, Ribes, Hamamelis, Fig. 135. — Phyllactinia coryloa. 1. Natural size, on chestnut leaf. 2. Perithecium enlarged. 3. Two asci. 4. Three spores. 5. Conidia-bearing hyphae. 6. Conidium germinating. After Anderson. Fraxinus, Asclepias, Catalpa, Cornus, Ulmus, Betula, Alnus, Corylus, Ostrya, Carpinus, Quercus, Castanea, Fagus, and Typha. Perisporiaceae (p. 127) Mycelium mostly superficial, dark, not dematioid, no typical ostiole. Cleistothecopsis Stevens & True C. circinans. Stevens & True Perithecia superficial, irregularly globular, 89.6-313.6 jx in di- PLANT DISEASE FUNGI 143 ameter, dark brown to black, no ostiole, surface reticulate, often with numerous short hairs extending out from surface cells, en- tirely pseudoparenchymatous, outer layer of darker, thick-walled cells; asci clavate, basal, evanescent, 8-spored, approximately 72-96 X 19-24 //; paraphyses present but evanescent; ascospores iiL.^^ Fig. 136. — A perithecium of Celistothecopsis with mature free spores. After Stevens and True. muriform, dark, obtuse at each end, usually with 4-7 transverse and 1-2 longitudinal septa, 24-36 x 9.6-14.4 yu. Its conidial form is Volutella circinans. Sporodochia scattered or often in concentric circles, usually in the centers of infected areas, numerous, black, subepidermal, erumpent, becoming cov- ered with loose mycelium, 1-2 mm. in diameter, 1 mm. in eleva- tion. Mycelium hyaline, becoming dark, rather coarse, 3.6-10.8 fi wide, branching irregularly, and with characteristic darkening of end cells where mycelium is superficial. Setae one to many, scattered throughout, dark brown to black, 125-240 fi long, 4 n Avide at base, tapering to apex. Conidiophores straight, simple, hyaline, few-septate, obtuse, 24-48 x 2.4 /x, bearing conidia acro- genously. Conidia falcate, acute at each end, continuous, hyaline, 19-26 X 3.6-7.2 fx. On onions, developing particularly during storage. The dark coarse, septate mycelium forms dense mats within the onion tis- sue, either inter- or intracellular or even superficial. Under suit- able conditions a sporodochium, which has been described both as 144 PLANT DISEASE FUNGI a pycnidium and as an acervulus develops and bears the spores. Perithecia are but rarely seen. Capnodiaceae (p. 127) Fungus superficial. Mycelium dematium-like or if straight- walled, slimy: hyphopodia rare. This family constituting the " sooty molds" ^ consists of numerous genera. They, so far as is known, do not penetrate the host at all and probably, strictly speaking, do not cause disease. They are especially abundant in the tropics and sub-tropics and are inju- rious in that they disfigure leaves or fruit. Those on the orange and camellia are of most importance. Frequently, especially in extra tropical regions, the mycelium only is present, usually consisting of char- acteristic, beaded cells, Fig. 137, which was once given the form genus name Fumago. Under favorable conditions perithecia and pycnidia also develop, both of these being variable in character thus rendering ex- ceedingly difficult the tax- onomy of this group. The mycelium alone is quite in- adequate for classification and, in the absence of peri- thecia, no classification is possible. These uncertainties have led to much confusion. Thus the form on Citrus has been variously placed in the genera Fum- ago, Capnodium, Meliola, Morfea and Limacinia; and even re- garded as consisting of three species bearing for example the names Limacinia citri, L. penzigi, L. camellise. All of these Arnaud unites under the name Pleosphaeria citri Arn. Fig. 137. — Beaded mycelium of the sooty mold. After Mendoza. 1 Arnaud, G. Contribution k I'etude des Fumagines Ann. d. i'ecole nationale d'agriculture de Montpellier, 10; 211, 1910-11; 12: 23, 1912. PLANT DISEASE FUNGI 145 Hemisphaeriales ' (p. 95) Perithecia dimidiate, superficial or subcuticular. Microthyriaceae Mycelium superficial, dark, filamentous or lacking, perithecia superficial, shield-shaped, black, radiate, Asci 4 to 8-spored; short, paraphyses usually present. Gloeodes (see p. 360) probably is an imperfect form of some member of this order. Diplocarpon Wolf D. rosae Wolf. (=Actinonema rosse) The vegetative body of the fungus consists of two parts, the subcuticular mycelium, made up of a net-work of branched radiat- ing strands, and the internal mycelium which furnishes nutriment for the subcuticular part and is connected with it by hyphse which penetrate the epidermal cells or pass between them. Single fila- FiG. 138. — D. rosse rhizomorph-like strands of mycelium. After Wolf. Fig. 139. — Vertical section show- ing the mycelium of D. rosse under the cuticle and also within the epidermis and meso- phyll. Alter Wolf. ments are often more or less coralloid in appearance. At certain definite points on the mycelium a stroma begins to form, seated directly upon the epidermal cells. From these arise the conidia or summer spores, which soon become divided by a cross wall. In the following spring perithecia develop on the overwintered leaves. iTheissen, F., and Sydow, H. Synoptische Tafeln. Ann. Myc. 15: 396, 1917. 146 PLANT DISEASE FUNGI Fig. 140. — D. rosae vertical section through an acervulus. After Wolf. Perithecia epiphyllous, spherical to discform, 100-250 fx in diame- ter, radiate; asci 70-80 x 15 m, 8-spored; spores 20-25 x 5-6 ii, un- equally, 2-celled, hyaline. Conidia in an acervulus, 18-25 X 5-6 M- Parasitic on rose leaves. Hypocreales ^- - (p. 95) The chief character 1^ separating this order from other Pyrenomycetes is Fia. 141.— D. rosae vertical section through a mature per- fUcv KvirrVi+ov /^r»lr»v irol ithecium. After Wolf. ^^^^ DHgnter COlOl yCl- low, purple, scarlet, red, etc. — and the more tender texture of its perithecia, — soft, fleshy, cottony, patellate or effused. The perithecium also differs from that of the preceding orders, excepting the last, in the possession of a distinct opening, ostiole, for the exit of spores. Perithecia globose to cylindric or flask-shaped, free on the sub- stratum, rarely subepidermal, or united by a common matrix, which varies from a cottony subiculum to a distinct fleshy stroma, wall membranous or at least not truly carbonous; asci cylindric, ^ Seaver, F. J. Hypocreales. North American Fungi. 3: 1, 1910. 2 Seaver, F. J. Some North Dakota Hypocreales. Bull. Torr. Bot. Club. 35: 527. PLANT DISEASE FUNGI 147 clavate or subovoid, mostly 4 to 8-spored but often becoming 16-spored by the separation of each original spore into two globose or subglobose cells ; spores simple or compound, hyaline or colored, globose to filiform. Conidia are usually produced freely, each genus usually possess- ing at least one form of free-borne conidia, while in some genera several different kinds of conidia are found. Pycnidia are rare. Often the ascigerous stage is nearly suppressed and rare when one or more of the conidial forms predominates. Such form genera as Fusarium, Verticillium, Tubercularia, Sphacelia, Sphaercstilbe and Isaria are connected with the Hypo- creales. The order includes over sixty genera and more than eight hun- dred species. Of these few genera contain important plant parasites. The rest are saprophytes, insect parasites, etc., of little or no economic significance. Only seven genera will be considered and they may be classified by the following key. Key to Genera of Hypocreales Spores 2-celled Stroma cottony 1. Hypomyces, p. 147. Stroma not cottony Spores hyaline 2. Nectria, p. 148. Spores brown 3. Neocosmospora. Spores 1-many celled Perithecium not blue 4. Calonectria, p. 150. Perithecium blue 5. Gibberella, p. 150. Spores filiform Asci preceded by conidia 6. Claviceps, p. 151. Asci preceded by smut-like chlamydo- spores 7. Ustilaginoidea, p. 153. Hypomyces (Fries) Tub Stroma an effused cottony subiculum, often of considerable ex- tent; perithecia numerous, usually thickly scattered and immersed in the subiculum, rarely superficial; asci cylindric, 8-spored; spores fusoid or fusifonri, usually apiculate, rarely blunt, 2-celled, hya- line; conidial phase variable. This genus contains but few saprophytes, the majority being parasitic, chiefly on the larger fungi. Chlamydospores and conid- 148 PLANT DISEASE FUNGI Fig. 142. — Hypomyces ochraceus. B, perithecia; C, asci and spores; D, spores; E, conidia; F, chlamy- dospores. After Tulasne. iospores develop, belonging to various form genera as Verticillium, Mycogone, Fuligo, Diplocladium, Dac- tylium, Sepedonium, Blas- totrichum. Allied to this genus are probably Mycogone rosea and M. perniciosa, which are destructive enemies of mushroom culture. (See p. 393.) Nectria Fries (p. 147) Stroma absent or tuber- cular, fleshy, bright col- ored; perithecia single or gregarious, on or in the stroma or among cottony hyphse, globose or ovate, walls fleshy, yellow, red or brown, smooth or hairy; ostiole papillate or not; asci cylindric or clavate, 8-spored; spores elongate, blunt or pointed, hyaline, rarely red, 2-celled, forming conidia in the ascus; paraphyses usually none. As conidial stages occur the form genera Cephalosporium, Tubercularia, Fusarium, Spicaria, Fusidium and Chaetostroma. Much doubt exists as to specific limitations, and as to the life his- tories of the species. Several are credited with causing serious diseases, most of them occurring as wound parasites and unable to effect entrance into sound tissue. Other species are saprophytes and harmless. N. cinnabarina (Tode) Fr. Stroma erumpent, tubercular, at first pinkish or yellowish-red, darker with age, 1-2 mm. high and broad; perithecia almost glo- bose, the ostiole rather prominent, becoming slightly collapsed, at first bright cinnabar-red, darker with age, granular, 375-400 ix in diameter; asci clavate, 50-90 x 7-12 ix] spores mostly 2-seriate, elliptic elongate, ends obtuse, slightly curved, 12-20 x 4-6 /i; para- physes delicate. Tubercularia vulgaris borne on the stroma is the conidial stage. Conidiophores aggregated into tubercular masses each 50-100 m PLANT DISEASE FUNGI 149 Fig. 143. — N. cinnabarina, perithecia in stroma, ascospores issuing in cirri; ger- minating spores. After Hartig. long; conidia on short lateral branches, elliptic, hyaline, 4-6 x 2 /i, no chlamydospores. The closely septate delicate hyphse grow rapidly through the wood or bark, penetrating nearly every cell, turning the wood black and collecting to form stro- mata on or in the bark. These stromata in fall or spring break through the epidermis and produce warty, gray to pink, excrescences, which at first bear profuse conidia both terminally and laterally on short stalks and later dark-red ascigerous structures; though the latter are much less common. The fungus is said to be unable to affect living cambium and cortex. It is found saprophytically on many decayed woody plants that have been frost killed, and parasiti- cally on pear, currant, linden, horse chestnut, Chinaberry, birch, elm, Carya, Prunus, maple, mulberry, oak, etc. Mayer germinated spores on a cut branch; the my- celium spread to and killed the main stem; tubercles appeared and during the following year perithecia developed on these tubercles. N. galligena Bres. = Fusarium willkommii Lind. Perithecia red, ovoid, 400-450 x 275-325 /x; ascospores ovoid, 1-septate, 14-16 x 5-7.25 /x; conidia cylindrical, mostly 5-septate, 57-73 X 4.75-6 ix, but 30% of all conidia may be 6-septate, with average length up to 82 /i. No true chlamydospores are present. A wound parasite, cause of canker on apple trees and associated with canker on various other trees. This fungus is often confused with Nectria ditissima TuL, a probable saprophyte, which has shorter ascospores, 12-14 /x long. N. cucurbitula Sacc. Perithecial clusters erumpent, often irregular in form, 1-2 mm. in diameter; perithecia densely clustered, bright red, ovate, with a prominent ostiole, rarely collapsing; asci cylindric to clavate, 75-100 X 6-8 ix] spores at first crowded and partially 2-seriate, finally becoming 1-seriate, lying obliquely in the ascus, broad, fusoid, rarely subelliptic, 14-16 x 5-7 ti. 150 PLANT DISEASE FUNGI Its hosts are spruce fir, pine, and other conifers. The fungus is usually a wound parasite, often following hail. Germ tubes from ascospores or conidia enter the cortex and develop a rich mycelium in the sieve tubes and soft bast. This advances most rapidly during the dormant period of the bast. White or yellow stromata the size of a pinhead appear and bear numerous conidia. Later come the red perithecia whose asco- spores ripen in winter or spring. Other species are on cherry, alder, arbor-vitse, ash, beech, birch, box elder, Chinaberry, dogwood, elm, fir, hazel, iEsculus, linden, maple, mulberry, oak, pine, spruce, walnut. Calonectria De Not.^- ^ (p. 147) Perithecia free, often closely gregarious, true stroma wanting but perithecia often surrounded by a radiate, white mycelium which may simulate a stroma; perithecia globose to ovate, red or yellow; asci elongate, 8-spored; spores elongate, more than 2-celled. C. graminicola (Berk. & Br.) Woll. = Nectria graminicola Berk. & B. Perithecia brown, average diameter 125-200 /jl (limits 75-300 n); ascospores fusoid, 1 to 3-septate, 12-15 x 2.75-3.75 /x. Conidia (Fusarium) ochreous to salmon-colored, 3-septate, 23- 26 X 3.25^ jjL, formed as a slightly curved comma. Instead of true chlamydospores a plectenchyma is present. Cause of seedling blight, snow mould disease, on cereals. Gibberella Saccardo (p. 147) Stromata tuberculate, more or less effused; perithecia cespitose or occasionally scattered on or surrounding the stroma; asci clavate, 8-spored; spores fusoid, 4 to many-celled, hyaline; conidial phase a Fusarium. G. saubinetii (Mont.) Sacc.^ Perithecia blue, 150-250 x 100- 250 fjL, scattered, papillate, free on the surface of the host or em- bedded in mycelium or on a stroma. Asci 60-76 x 10-12 /x. As- ^ Weese, J. Beitrage zur Kenntnis der Gattung Calonectria. Myc. Cent. 4: 121, 1914. 2 Wollenweber, H. W. Studies on the Fusarium problem. Phytop. 3: 24, 1913. ^ Atanasoff, D. Fusarium-l)light (scab) of wheat and other cereals. Jour. Agr. Res. 20: 1. 1920. PLANT DISEASE FUNGI 151 oospores sickle-shaped, 3-septate, 20-30 x 3.75-4 /j,. Conidia similar to tliose of the section discolor of the genus Fusarium, 3 to 5-septate, 30-60 x 4.25-5.5. fx. No true chlamydospores are present. The cause of kernel scab and seedling blight, foot disease, on cereals especially wheat, emmer, rye, oats, spelt, and corn, also on clover. On the roots and bases of young small grains enumerated above the fungus causes rot followed by wilting; on the nodes or heads blighting results. The mycelium and the conidial stages often coat the grains and heads of cereals with red or pink. Perithecia are less common as shin- Fig. 144.— Conidia of g. ing dark dots on the grains in the late season. nasoff!^^"" *^^ '^*^" The Fusarium stage is also the cause of a clover and alfalfa disease and the fungus by inoculation and cul- ture is shown to be identical on wheat, clover, barley, rye, spelt, emmer, oat and some other grasses. It is carried from season to season on infected seed and causes large loss of young plants. It survives the winter also in perithecia. Root infection follows in about seven days after inoculation : head infection in 3-6 days. Claviceps Tulasne (p. 147) Sclerotium formed within the hypertrophied tissues of the ovary of the host, succeeding the conidial stage which is a Spha- celia; stroma erect, with a long sterile base and a fertile, 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, 8-spored; spores hyaline, continuous. Several species are recorded all affecting the ovaries of the Gramineae. 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 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, hya- 152 PLANT DISEASE FUNGI line, 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. Fig. 145. — C. purpurea. D, Sphaeelia stage; E, germinated sclerotia; G, section of stroma; H, section of a perithecium, /, ascus with spores. After Tulasne. 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, numerous conidia and a sweet fluid is exuded. The conidia, carried by in- sects, spread summer infection. Later the stroma, losing a large PLANT DISEASE FUNGI 153 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. This species is differentiated into a number of biologic races. C. microcephala (Wallr.) Tul. infects numerous grasses being especially destructive to blue grass. Two species C. paspali S. & H. and C. rolfsii S. &. H. occur on Paspalum. Ustilaginoidea Brefeld (p. 147) Sclerotium formed in the grain of the host, resembling super- ficially a smut sorus, in the center composed of closely interwoven hyphse, 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 as- cigerous stage, the other on rice, the ascigerous stage of which 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 spherical, about 5 mm. in diameter; conidia spherical, at first smooth- walled, hyaline, at maturity echinulate and ohve green, 4-6 M- The short thick walled hyphse of the interior of the sclerotium are closely interwoven to a false tissue, toward the periphery they become parallel and are directed radially. Here a yellow layer is produced and spores are formed laterally on the hyphse. When mature the spores are in mass dark olive-green and form an outer green layer on the Fig. 146. — U. virens; a, spores germinated in water; b, germinated in bouillon. After Fulton. 154 PLANT DISEASE FUNGI sclerotium. The spores germinate in water, producing a vegeta- tive mycelium which bears secondary spores and somewhat re- sembles the mycelium of the Ustilaginales. Dothideales (p. 95) ' Ascomycetes, simple or stromate; ascigerous loculi without a proper membrane. Conidia of various forms are present. Though numerous genera occur, only the two following need be mentioned. Phyllachora Nitschke ^' ^ Stromata in the mesophyll and remaining covered, with cutic- ular or epidermal clypeus; structure prosenchymatic-dothideoid, or of more or less irregular hyphse; loculi sunken in the leaf, the apex growing into the clypeus; spores 1 -celled, hyaline; paraphysate. Three hun- dred twenty-two species are given by Theissen & Sydow on many hosts. P. graminis (Pers.) Fcl. Stromata variable in size and form but usually about 4x1 mm., caus- ing conspicuous, black spots on leaves, visible from both sides; locules 186-220 /x in diameter, 145-175 deep; asci short-pedicellate, cylindric, 60-70 X 8-10 fi, 8-spored; spores elliptical, hyaline, 9-11 x4-5 fj,; paraphyses filiform. This fungus occurs on many grasses with but slight injury to them. As generally understood it is a collective species which will doubtless be segregated later. Many other species are recorded on various grasses and one on corn. Fig. 147. — P. gram- inis. B, stroma in section; C, an ascus and spores. After Winter. 1 Theissen, F. and Sydow, H. Die Dothideales Ann. Myc. 13: 149, 1915. 2 Dalbey, Nora. Phyllachora as the cause of a disease of corn, and a general con- sideration of the genus Phyllachora. Trans. 111. Acad. Sc. 10: 230, 1917. ^ Clevenger, J. F., Notes on some North American Phyllachoras. Jour. Myc. 11: 159, 1905. PLANT DISEASE FUNGI 155 Dibotryon Theissen & Sydow Loculi closely placed on a compact stroma, free; connected with the stroma by a short basal column which also affords the thin cov- ering of the locules; no ostiole; locales 230 n high x 180-220 /jl broad. ^ IsS \^ 'O d Fig. 148. — D. morbosum. b, magnified section of a knot showing the peri- thecia; c, conidiophores and conidia; d, seotion of a perithecium showing numerous asci, one of which is shown more highly magnified at e; /, sev- eral of the two-celled ascospores germinating in water. After Longyear. 156 PLANT DISEASE FUNGI D. morbosum (Sch.) Theiss. & Sydow ^' - Plowrightia morbosa (Schw.) Sacc. Stromata formed within the tissues of the host plant, erumpent, tubercular or cushion-shaped, depressed or elevated, smooth, later frequently wrinkled, white within; elongate, up to 2 or 3 dm. long; perithecia scattered, often entirely suppressed; asci cylindrical, 8-spored, about 120 jjl long; spores 2-celled, hyaline to light green, variously arranged in the ascus, 16-20 x 8-10 fx, ovate, the cells usually unequal; paraphyses filiform. Conidia (=Cladosporium sp.) produced 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 conidiophore, obovate, unicellular, light brown, about 6- 8 X 2-5 fi. 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. It has been shown that biologic specialization occurs. The mycelium invades the cambium of twigs, usually in early spring, 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 visi- ble in this black stroma and in January or later the asci mature. That the fungus is the actual cause of the black knot was first demonstrated by Farlow in 1876, though the fungus was de- scribed as early as 1821 by Schweinitz. ^ Formerly known as Plowrightia morbosa this species was, together with cer- tain species of Botryosphseria that lack paraphyses, recently moved into a new family, the Pseudosphaeriales, by Theissen and Sydow. 2 Stewart, A. Some observations on the anatomy and other features of "black knot." Am. Jour. Bot. 1: 113, 1914. See Annales Mycologi 16: 1, 1918. PLANT DISEASE FUNGI 157 Sphaeriales (p. 95) 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 crust aceous 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 ascigerous form developing only after the death of the part of the host in- volved. The order is very large, embracing according to Lindau some eighteen families and over six thousand species. Key to Families of Sphaeriales Perithecia free, either without a stroma, partly seated in a loose mass of mycelium, or ses- sile above an imperfect stroma Walls of the perithecia thin and membra- nous; asci soon disappearing. Perithecia usually sunken, with only short hairs about the mouth 1. Sordariaceae, p. 158. Walls of the perithecia coriaceous or carbon- ous Perithecia either entirely free, or with the base slightly sunken in the substra- tum or stromatic layer Stroma wanting or only thread-like or to- mentose Mouths of the perithecia mostly in the form of short papillse 2. Sphaeriaceae, p. 159. Mouths of the perithecia more or less elongate, often hair-like 3. Ceratostomataceae, Perithecia without a stroma, and sunken in the p. 164. substratum, or within a stroma Stromata none; perithecia rarely united above by a black tissue (clypeus ) Asci not thickened at the apex, mostly pro- jecting at maturity. Walls of the 158 PLANT DISEASE FUNGI perithecium thin, coriaceous; mouth mostly short or plane Asci clinging together in fascicles, without paraphyses 4. Mycosphaerellaceae, p. 165. Asci not fasciculate; with paraphyses. . 5. Pleosporaceae, Asci usually thickened apically, opening by p. 178. a pore; perithecia usually beaked, without a clypeus 6. Gnomoniaceae, Perithecia firmly imbedded in a stroma, the p. 189. mouths only projecting, or becoming free by the breaking away of the outer stro- matic layers Stromata fused with the substratum Conidia produced in pycnidia 7. Valsaceae, p. 199. Conidia developed from a flattened surface 8. Melanconidaceae, Stromata formed almost wholly of hard- p. 202. ened fungal hyphae Spores rather large, 1 to many-celled, hyaline or brown, conidia mostly in cavities in the stroma 9. Melogrammatacese, Spores 1-celled, rarely 2-celled, black- p. 203. ish brown. Conidia developed on the upper surface of the young stroma 10. Xylariaceae, p. 207. Sordariaceae (p. 157) 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 papilli- form beaks; asci usually very delicate, cylindric, 8-spored; spore, usually dark-colored; paraphrases abundant. A small order, chiefly dung inhabiting. Acanthorhynchus Shear Perithecia scattered, submembranous, buried, beaked, the beak with non-septate spines; asci opening by an apical pore; paraphyses present, septate; spores contirmous, brownish-yellow. There is a single species, A. vaccinii Sh. which produces rot of cranberries, also leaf spots, but the fructification of the fungus PLANT DISEASE FUNGI 159 is rarely found in nature except on old fallen leaves. Remarkable appressoria are produced by the gerni tubes from the spores, Fig. 150. Fig. 149. — A single perithecium of A. vaccinii taken from a pure cul- ture on corn meal. After Shear. Fig. 150. — Acantho- rhynchus; 16, a ger- minating ascospore bearing the peculiar appressorium. 17, view from above. After Shear. Sphaeriaceae (p. 157) 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 Sphseriaceae Perithecia hairy above, rarely smooth above and hairy beneath Spores 1 or 2-ceIled; perithecia thick, leath- ery or carbonous Spores hj^aline 1. Trichosphagria, p. 160. Spores dark colored, 2-celled 2. Neopeckia, p. 161. Spores more than 2-celled Perithecia thin, leathery or cuticularized 3. Acanthostigma, p. 161. Perithecia thick, carbonous or woody; spores spindle-form, many-celled, concolorous, hyaline or brown 4. Herpotrichia, p. 162. Perithecia smooth, neither hairy nor tuber- culate; spores 1-celled, dark, unappen- daged; perithecia carbonous 5. Rosellinia, p. 163. 160 PLANT DISEASE FUNGI Trichosphaeria Fuckel (p. 159) Perithecia usually free, globose, woody or carbonous, hairy, ostiole flat or papillate; asci cylindric, 8-spored; spores 1 to 2- celled, hyaline; paraphyses present. The species are mainly saprophytes. T. sacchari Mass. Perithecia broadly ovate, dark-brown, beset with brown hairs; spores elongate-ellipsoid, 1-celled; the conidial forms are various ( :i ■'.'i^-- ■via;;-,--,;? Fig. 151. — 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 ju, (2) The macroconidia ( = Thielaviopsis ethaceticus) see p. 396, are often found forming intensely black, velvety layers lining cracks and cavities in diseased canes. (3) Microconidia produced on the surface in Oidium-like chains. Their connection with this fungus is disputed and uncertain. It is a sugar-cane parasite. PLANT DISEASE FUNGI 161 Neopeckia Saccardo ^ (p. 159) Perithecia carbonous, superficial, setose, papillate, asci 8-spored, many-paraphysate ; spores dark, 2-celled. N. coulteri (Pk.) Sacc. Peri- thecia spherical, 0.32-0.5 mm. in diameter, immersed in a dark brown, felt-like subicu- lum, 0.4-0.53 mm. thick; asci cylindrical, 150-185 x 15-18 /x; paraphyses filiform, fugacious; spores obliquely uniseriate in the asci, blunt-elliptical, at first pale brownish, later dark- brown, 1-septate, constricted at the septum, 20-29 x 9.5-10 ju. On living; leaves and twigs F^^- 152.— N. coulteri a penthecium, ascus and „ . spores. After Sturgis. of pme. Acanthostigma de Notaris (p. 159) Perithecia free, globose or ovate, very small; walls leathery, black, be- set with stiff bristles, ostiole short; asci usually cylindric, rarely ovate, 8-spored; spores spindle-shaped, multi- cellular by cross walls, hyaline; par- aphyses few or none. A. parasiticum (Hartig) Sacc. Perithecia globose, minute, with rigid divergent hairs, 0.1-0.25 mm. in diameter; asci 50 /i long, early dis- appearing; spores fusoid, straight or .curved, smoky, 15-20 jjl, continuous or 2 to 3-septate. Common on leaves of fir, hemlock and other conifers. The hyaline mycelium grows on the lower sides ^ , -o T. u • r A . . of branches and on the leaves kill- FiG. lo3. — Penthecium of A. parasiti- • , i i . , cum, showing ostiole, bristles, asci, lug thcm and mattmg them to the paraphyses and spores. After Hartig. ^ ^ mi ^• i i • i , branches. The mycelial cushions later turn brownish and eventually very small perithecia form on them. ^Sturgis W. C, Herpotrichia and Neopeckia on Conifers. Phytop. 3: 152, 1913. 162 PLANT DISEASE FUNGI Herpotrichia Fuckel (p. 159) 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 grow- ing on woody plants, are mostly saprophytes. H. nigra (Pk.) Sacc. Perithecia spherical with slightly prominent ostiole, 0 . 25-0 . 45 mm. in diameter, semi-immersed in a dark brown, felt-like subiculum, 0.27-0.5 mm. thick; asci FiQ. 154. — H. nigra, a perithecium, ascus and spores. After Sturgis. Fig. 155. — Herpotrichia. B, ascus; C, spore. After Winter. club-shaped, 128-155 x 14-18 /x; paraphyses filiform, fugacious; ascospores irregularly biseriate in the asci, elliptical, at first 1 to 3-septate, hyaline, later 3-septate, more or less constricted at the septa, pale to darker olivaceous-brown, 22-33 x 8.5-9 ix] conidia borne singly on short hyphae, dark brown, 3 to 6-septate, con- stricted at the septa, 27.5-29 x 9-10 ^t. On living leaves and twigs of spruce, pine, juniper and fir. A felt-like growth of dark brown mycelium spreads over the affected leaves killing them and portions of the branches. PLANT DISEASE FUNGI 163 Rosellinia Cesati & de Notaris (p. 159) Perithecia superficial, but often with the bases more or less sunken in the substratum, coriaceous or carbonous; brittle, spher- ical 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 con- sists of a vigorous white mycelium, which remains for a long time sterile, developing large branching and interlacing rhizomorphs (Dematophora) which later become brown. These resemble somewhat, but are distinguishable from, the rhizomorphs of Armil- laria mellea; again, they are Rhizoctonia-like. There are over one hun- dred seventy species, mostly saprophytic. R. necatrix (Hart.) Berl. A destructive fungus, long known as Dematophora neca- trix, possesses a white my- celium which invades the small roots, thence passes to larger ones, extending in trees through the cambium and wood to the trunk, occa- sionally rupturing the • bark and producing white floccose tufts. Sclerotia of one or more kinds are produced in the bark and often give rise to conidia on tufted conidiophores in a Coremium-like layer (Fig. 156). The mycelium, when old, turns brown and produces large branch- ing, interlacing rhizomorphic strands which spread to the soil, or wind about the roots. Perithecia found on old wood, long dead from such attack, be- long to the genus Rosellinia and are believed to present the as- Fig. 156. — R. necatrix. 4, coremium and conidia; 5, perithecia extruding spores; 6, asci and par- aphyses. After Hartig, Prillieux and Viala. 164 PLANT DISEASE FUNGI cigerous form of Dematophora necatrix. Similar claims of rela- tionship of this fungus to several other genera have been made and its actual position cannot be considered as established with certainty. The fungus attacks many kinds of plants. R. caryae Bonar.^ Perithecia superficial or slightly sunken in the outer bark, scattered or gregarious, carbonaceous, brittle, slightly bristly or smooth, broadly flask-shaped, with a short distinct ostiole; asci cylindric, 8-spored, averaging 50 x 6-8 //; spores uniseriate, sub-globose, one celled, dark brown, 5-7 x 3 . 5- 4.5 /x; paraphyses filiform. Conidia=Dothichiza caryae Bonar. Pycnidia scattered, erum- pent, dome-shaped, non-ostiolate, irregularly dehiscent, wall dis- tinct except at base, hymenial layer continuous over the inner surface, conidiophores short; spores 1-celled, hyaline, broadly fusoid, 5-7 X 2 . 5-3 /x. The cause of canker on Carya. R. massinkii Sacc. was reported by Halsted on hyacinth bulbs. R. quercina Hartig is parasitic on roots and stems of young oaks. R. radiciperda Mass., closely allied to R. necatrix, affects a large number of hosts, among them apple, pear, peach, cabbage, and potato. Ceratostomataceae (p. 157) 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. 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 Hedgcock who recognizes several species as discoloring lumber. C. pilifera (Fr.) Wint. has been described in detail by von Schrenk as the cause of a blue color in pine wood. 1 Bonar, Lee. The life history of Rosellinia Caryce Sp. Nov. causing a hickory canker and disease. Phytop. 12: 381, 1922. PIANT DISEASE FUNGI 165 Mycosphaerellaceae (p. 158) Perithecia mostly subepidermal, rarely subcuticular, finally more or less erumpent or even superficial, membranous or leathery, 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-celled or not clearly 2-celled Perithecia very small, on a basal growth of thick branched hyphse 1. Ascospora, p. 165. Perithecia without such a basal growth, spores usually unequally 2-celled ... 2. Guignardia, p. 166. Spores 2-celled Perithecia produced on living plants.. . . 3. Stigmatea, p. 171. Perithecia appearing only after the death of the host 4. Mycosphserella, p. 171. Spores several-celled, hyaline Spores elongate transversely divided, many celled 5. Sphaerulina, p. 177. Spores muriform 6. Pleosphaerulina p. 177. Ascospora Fries Perithecia borne on a subiculum of thick, brown, much-branched hyphse, globoid, black, carbonous; asci clavate, clustered, 8-spored, small; spores 1-celled, hyaline; paraphyses none. A. beyerinckii Vuil. Perithecia black, depressed- globose, apapillate; ostiole indistinct or absent, 100-130 fx in diameter; spores elliptic-fusoid, ends obtuse, continuous, hyaline, guttulate, 15 x 5-7 fx. Conidia, 1. (=Phyllosticta beyerinckii) pycnidia fig. 157.— Ascospora globoid with hyaline spores. AfTer^'wlnter. ^ ^ ^ " Conidia, 2. (=Coryneum beyerinckii) conidio- phores short, crowded, from a minute subepidermal stroma; co- nidia single, elhptic-oblong, 1 to 5-septate, brown, about 36 x 15 /x. On drupaceous hosts, especially the peach, causing spots on the leaves, fruit and shoots, accompanied by a gummy exudate. 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 166 PLANT DISEASE FUNGI 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- FiG. 158 — 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 ascigerous stage was found. Guignardia Viala & Ravaz (p. 165) Perithecia sunken, globoid or flattened, black, leathery; ostiole flattened or papillate; asci clavate, 8-spored; spores ellipsoid or fusiform, hyaline, somewhat arched, 1 or 2-celled; paraphyses none. Over one hundred thirty species are known. Some are impor- tant parasites. Conidial forms are found in Phyllosticta and Phoma. G. bidwellii (Ellis) V. & R. Perithecia minute, globose, subepidemial, erumpent, perforate; asci clavate-cylindric, obtuse, 60-70 x 10-13 n; spores elliptic to oblong, continuous, 12-17 x 434~5 M- Conidia ( = Phoma uvicola, Phyllosticta labrusca?) borne in pycnidia 180 x 180 fx, subepidermal, elliptic, thick-walled; conid- iophores short, simple; conidia ovate to elliptic, 8-10 x 7-8 fi. Fili- form microconidia ''spermatia" are borne in flask-shaped pyc- nidia, 0.1-0.2 x 0.45-0.46 m- PLANT DISEASE FUNGI 167 The fungus has been placed successively in the genera Sphseria, Phj^salospora, Laestadia and Guignardia. Perithecia were first found in 1880 by Dr. Bidwell in New Jersey. They are abundant on berries which have wintered out of doors. oscospore germ/naf/o/T Fig. 159. — Diagrammatic section of a perithecium containing ascospores. Germination of a spore at the right. After Reddick. It is found on all green parts of Vitis and Ampelopsis, the as- cigerous stage common only on the mummified fruits. The myce- lium kills the host cells and causes collapse of the spongy paren- chyma. Reddick describes the development of the spots essentially as follows : On the leaves the first evidence of the spot is the slight blanching of a single one of the smaller areolae of the leaf. Soon the blanch- ing extends to adjacent areolae, 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 little later the margin is a brownish band and the brown gradually ex- tends inward until the whole spot is covered. As soon as the brown 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 leaves a marginal band of a deeper brown than 168 PLANT DISEASE FUNGI the central disc. Spots vary in size from 1 mm. up to 8 mm. in di- ameter, but in general are 3 to 5 mm. or larger. Occasionally the whole leaf is destroyed but this the result of the coalescence of jorcs. Germinated @E^ Spores Fig. 100. — Diagrammatic section through a pycnidium, showing how the spores are produced and how they germinate. After Reddick. many spots. When the spot has attained full size pycnidia pro- trude from under the cuticle and either dot the entire surface of the spot with 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 the leaf on ^IpJ such varieties as have leaves which are smooth beneath. The pycnidia, however, have never been seen on the under side of the leaf in our va- rieties. On stems, tendrils, pedun- cles, petioles and leaf veins the spot in its first appear- ance is a small darkened de- pression 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 Fio. IGl. — Section of a pustule showing microco- nidia. After Longyear. PLANT DISEASE FUNGI 169 this occasionally happens, rarely so on peduncles, and quite com- monly 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 shght as to be detected only by careful observation. It rapidly becomes more apparent, due to the appearance of a brownish line at the margin. 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 diameter, 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 light brown one which have in some cases a much lighter line between them. The aureola 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 white center of the spot. In five hours more they are so numerous as to give a blackish ap- pearance. In New York, Reddick found that the asci began 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 thrown to a height of 2 to 4 cm. There is at one end of the ascospore 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 determined 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 hyahne appendage though others by careful study fail to find it. These spores often live Fig 162.— G. bidwellii; 26, nearly mature ascus with spores; 27, mature ascospores; 28, ger- minating ascospores, 29, same with appres- soria. After Reddick. 170 PLANT DISEASE FUNGI over winter. The microconidia which develop in pycnidia similar to those of the macroconidia do not occur so abundantly early in the season as they do later and seem to be mainly limited to the fruits. Sporeless pycnidia, pycnosclerotia, also occur and may eventually develop into perithecia. Conidia on hyphse, of questionable relation- ship 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 re- quired. 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- oculations under all conceivable conditions, failed utterly of posi- tive results. G. vaccinii Sh. Perithecia on young fruit or flowers, subepidermal, globose, walls thick, carbonous; asci clavate, 60-80 }i long; spores elliptic or subrhomboidal, hyaline, becoming tinted. Conidia (=Phyllosticta) borne in pycnidia similar to the perithecia but thinner-walled, 100-120 11] conidia hyaline, obovoid, 10.5- 13.5 X 5-6 ix. On Vaccinium. In the decaying berries all sporing forms of the fungus are rare though in the softened tissues fungous hyphse abound. Transferred to culture media these hyphse grow readily and produce spores abundantly. G. ffisculi (Pk.) Stew.i Perithecia 175 /z broad, covered by epi- dermis; asci subclavate; spores hyaline, 7-10x5-6 ^i. Conidia (= Phyllosticta pa vise Desm. = P. sphseropsidea E. & E.) epiphyl- lous; spots reddish-brown, scattered or confluent, 1-2 cm.; pycnidia scattered, immersed, punctiform, erumpent above, subepidermal; conidia globose to broadly ellipsoid, hyaline, 12-15 x 8-10 ix. On horse chestnut causing leaf spot. ^ Stewart, V. B. The leaf blotch disease of horse chestnut. Phytop. 6: 5, 1916. Fig. 163. — A vertical section of a perithecium of Guig- nardia vaccinii, showing asci. After Shear. PLANT DISEASE FUNGI 171 Stigmatea Fries (p. 165) Perithecia subepidermal, or subcuticular, thin, black; asci ob- long, subsessile, 8-spored; spores ovoid-ellipsoid, 2-celled, yellowish or hyaline; paraphyses present. The ascigerous stage of two spe- cies of Entomosporium are said by Lindau to belong to this genus. Atkinson, however, places them in the genus Fabraea, see p. 112. S. juniperi (Desm.) Wint., is found on living leaves of Juniperus and Sequoia. Perithecia scattered, lenticular or subhemi- spheric, rough, 200-300 ix in diameter, asci rounded and obtuse above, abruptly tapering below into a short stipe, 60-70 x 20 m; spores ^^^ i64._stigmatea. ovate-lanceolate, unequally 2-celled, yellowish- Asci and spores, hyaline, 16-25 x 6-8 ii. Mycosphaerella Johans.^ (p. 165) Sphserella Ces. & De Not. 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 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 Septogloeum. 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. M. fragariae (Schw.) Lind. Perithecia on leaves are produced late in the season, globose, subepidermal, membranous, black, thin-walled; asci few, clavate, 8-spored, 40 ix long; spores hyaline, 2-celled, with acute tips, 15 x 3^ At. Conidia ( = Ramularia tulasnei) abundant in early summer on reddish spots, stromatic, conidiophores simple; conidia elliptic, 20-40 X 3-5 )Uj 2 to 3-celled. On strawberry. The life history was first studied in 1863 by the Tulasne brothers 1 Grove, W. B. Sphserella vs. Mycosphaerella. Jour. Bot. 40: 89, 1912. 172 PLANT DISEASE FUNGI under the name Stigmatea. The generic name was changed to Sphserella in 1882 and later to Mycosphserella, because the name Sphserella was preoccupied by an algal genus. The slender mycelium pervades the diseased areas disorganizing the host cells and resulting in reddish coloring of the sap. Ob- servations indicate that the mycelium or portions of it can re- main alive over winter in the host tissue ready to produce abun- dant conidia in the spring. The common conidial stage is the Ramularia-form 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 numer- ous ''spermatia" 1x3^. Perithecia abound in autumn. These are larger than the speniiogonia and are usually embedded in the leaf tissue, though they sometimes appear superficially. Co- nidiophores are often borne directly on the perithecium wall. As- cospores germinate within the ascus. From the mycelium re- sulting from ascospores typical summer conidia have been secured. M. grossulariae (Fr.) Lind. Perithecia hypophyllous, gregarious, spherical, with minute ostiole, black; asci short-pedunculate, clavate, 55-66 x 8-12 fx; spores fusoid, filiform, curved or straight, uniseptate, hyaline, 26-35 X 3-4 M. On the gooseberry, conidia= Septoria ribis Desm. M. rubina (Pk.) Jacz. Perithecia minute, gregarious, submembranous, obscurel}" papil- late, subglobose or depressed, erumpent, black; asci cylindric, subsessile, 70-80 x 10-12 fx; 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 Cer- cospora cerasella common on cherry. M. aurea Stone, on Ribes, has as a conidial stage, Septoria aurea E. &. E. PLANT DISEASE FUNGI 173 M. rubi Roark.^ Perithecia mainly hypophyllous, usually gregarious, erumpent, globose, 60-80 ix in transverse diameter with a short papilliform ostiole; asci aparaphysate, eight-spored, 42- 45 X 8-10 ix] ascospores hyaline, fusiform, of two equal cells, straight or slightly curved, 20-25 X 3.50^.25 At; conidial stage (=Septoria rubi West.) The cause of leaf spots on Rubus. M. nigerristigma Higgins. Perithecia black, on spots killed by pycnidial mycelium or scattered over the entire leaf, 90-110 x 45- Fio.165.-M. nigerristigma. ^5 M, immcrSCd, with the short beak pro- Mycelium ^ within the truding; asci clustered, aparaphysate, 35-45 showing constrictions X 7 /ii sporcs fusiform, colorlcss, l-septatc, 16- where passing through _^ o C^ Q walls of host cells. After ZY X Z.o~0 fJL. ^'^^'''^- Pycnidial stage: spots at first glaucous but soon turning brown, often dropping out, 2-5 mm. in diameter; pycnidia colorless or light brown, amphigenous, immersed, globose, with a single large ostiole; spores colorless, long, slender, Fig. 166. — M. niggeristigma. Mature pycnidium. After Higgins. Fig. 167. — M. niggerristigma. Mature perithecium with asci and spores in various stages of development. After Hig- gins. flexuous, 35-56 x 2-3 fj,, continuous or 1 to 4-septate. ''Sper- matia" produced in '^spermogonia" or in the pycnidia in late autumn, 4-5 x 1 ^u. Pycnidial stage parasitic in leaves of Prunus pennsylvanica, ascogenous stage saprophytic in leaves of the same host. M. sentina (Fr.) Schr. 1 Roark, E. W. The Septoria leaf spot of Rubus. Phytop. 11: 328, 1921. 174 PLANT DISEASE FUNGI Perithecia, 80-110 ii] on dead spots of leaves, the long ostiole erumpent; asci clavate, 60-75 x 11-13 /a, colorless; spores fusi- form, curved or straight, 26-33 x 4 /i. 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 /x. On pear and apple. The conidial form was mentioned in America as early as 1897 by Atkinson. The ascigerous stage was demonstrated, by Kle- bahn in 1908. 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. M. citruUina (C. O. Sm.) Gros. Perithecia roughish, dark-brown or black, de- pressed-globose to inverted top-shaped, usually with a papillate ostiole, densely scattered, erum- pent, 100-165 /x; asci cylindric to clavate, 45-58 X 7-10 fx', spores hyaline, oblong-fusoid, con- stricted at the septum. Conidia (=Diplodina citrullina). Pycnidia similar to the perithecia, spores 2-celled, hya- FiQ. 168.— M. sentina. line. Straight or curved, more or less cylindric, Conidial layer, co- irk_iQ ^ Q_Pi nidiophores and co- -'-O loXoO/i. bahn ^^^^^ ^^^' ^^^ fungus was isolated in pure culture by Grossenbacher from muskmelons by direct trans- fer 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 inoculation. The brownish pycnidia originate from an extensive subepidermal, partially cortical, much-branched, brownish mycelium but soon break through and appear almost superficial. When moistened spores issue in coils. Darker perithecia, nearly superficial, are found on old diseased spots. Both ascospores and conidia are capable of causing infection. Inoculations on pumpkin and water- melon gave positive results. PLANT DISEASE FUNGI 175 M. tabifica (P. & D.) Johns. Perithecia rounded, brown; asci oblong-clavate, 8-spored; spores hyaline, upper cell larger, 21 x 7.5 /x. Pycnidia (=Phoma) subglobose; co- nidia elliptic, hyahne, 5-7 x 3.5 /x, escap- ing as a gelatinous cirrus. This conidial form, common on beets causing leaf spot throughout the summer, ^^ is said to be connected with M. tabifica ^T' the perithecial form, which is found upon ^^^ the dead petioles at the end of the season. The conidial stage is variously known as Phoma betse, Phoma sphserosperma, Phyllosticta tabifica. The Phoma-forai from stems and rotten roots and the Phyllosticta-fornis from leaves were both studied in pure cultures on many media and many inoculations were made, all leading to the conclusion that the Phoma and the Phyllosticta are identical. 169. — M. sentina, peri- thecium and asci. After Kle- bahn. ^"^m^^^^ Fio. 170. — M. citrullina, A, pycnidium (Diplndia) in section, B and C, perithecium and an ascus and spores. After Grosscnbacher. M. tulasnei Jacz. Perithecia subglobose, minute; asci cylindric fusoid; spores oblong, rather pointed, upper cell in the ascus somewhat larger than the others, 28 x 6.5 /x. 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; 176 PLANT DISEASE FUNGI conidia often in chains of 2 or 3, subcylindric pale-olive, 1 to 3-septate, 10-15 x 4-7 /i. (2) ( = Hormodendrum cladosporioides Sacc.) Hyphse erect, simple, bearing apically or laterally a tuft of small, elliptic, continuous, brown conidia in simple or branched chains. It is the cause of serious disease of cereals and is found also parasitic on pea, apple, raspberry, cycad, agave and as a sap- rophyte almost anywhere. M. gossypina (Atk.) Earle Perithecia ovate, blackish, partly immersed, 60-70 x 65-91 n; asci subcylindric, 8-10 x 40-45 /jl; spores elliptic to fusoid, con- stricted at the septum, 3-4 x 15-18 ^u. Conidia ( = Cercospora gossypina) ; hyphse flexuose, brown, 120-150 /JL high; conidia attenuate above, 5 to 7-septate, hyaline, 70-100 X 3 /x. On cotton. The intercellular mycelium is irregular, branched, septate, and produces tuberculate stromata from which the brownish hyphse arise. The perithecia, much less common, are partly immersed in old leaves. M. pinodes (Berk. & Blox.) Stone. ^ Perithecia numerous, 100- 140 /x; asci oblong-c^dindric, 58-62 x 12 /x; spores 2-rowed, 14- 16 X 5 /x. Pycnidia ( =Ascochyta pisi). Spots variable in size, roundish, yellowish with brown margin; pycnidia centrally located, black, of angular cells, 5-7 /x; ostiole rounded, surface reddish brown. On peas, beans, vetch, Cercis, etc. The pycnidia are visible on the dead areas of the stems, leaves, pods or seeds. The mycelium hibernates in affected seeds, reduces their germinating power and carries the fungus over to the succeeding crop. Inoculations with ascospores have resulted in about five days in charcteristic brown lesions resembling in every way those caused by Ascochyta pisi. In ten days pycnidia with mature Ascochyta spores were obtained. M. ontarioensis Stone ( = Ascochyta lathyri) occurs on Lathy- rus (grass pea). M. brassicicola (Duby) Lindau ( = Phyllosticta brassicicola McAlpine) occurs on cabbage and cauliflower causing leaf spot. M. ulmi Kleb. This is the ascigerous stage of Phleospora ulmi ^ Stone, R. E. The life history of Ascochyta on some leguminous plants. Ann, Myc. 10: 564, 1912. PLANT DISEASE FUNGI 177 (Fr.) Wallr. = Septogloeum ulmi (Fr.) Bri. and Cav. On elm numerous, small, reddish-brown spots appear on the upper side of the leaves, which gradually turn yellow, the margin becomes brown and rolls up, and the leaves fall early in the season. The spores ooze out in minute cirri which dry on the lower side of the leaf surface and form small whitish patches. M. rosigena E. &. E. Amphigenous on reddish-brown, purple-bordered spots which are about 3-4 mm. in diameter; perithecia thickly scattered over the spots, minute, 60-75 />t, partly erumpent, black; asci subclavate to oblong, 25-30 x 8-10 yu; spores biseriate, clavate-oblong, hyahne, 1-septate, 10-12 x 2 ^t, ends subacute. It causes leaf spots of rose. Other species are on quince, grape. Citrus, sugar-cane, rice, Morus, oak, lime, hazel, beech, balsam, yew, larch, coffee, Poplar, pecan, Hedera, Ficus elastica, primrose, lilies, gladiolus, ferns. Sphaerulina Saccardo (p. 165) Perithecia globose, membranaceous, ostiolate, asci aparaphysate, 8-spored; spores cylindrical or oblong, 3 to many- septate, hyaline. S. trifolii E. Rostr.i Spot circular, 2-3 mm. in diameter; perithecia epiphyllous; asci 8-spored; spores hyaline, oblong, 3-septate, 32-33 X 12-15 jjL. The disease on various clovers is exhibited at first as minute, black lesions on the leaf blades, petioles and stipules, often the leaflets turn yellow and fall. Later these small spots enlarge and have a light brown to gray center surrounded by a dark reddish-brown ^":^''J}:::^r±^ .^±^1 margin; lesions occur also on the pe- duncle, calyx and corolla. an immature ascus from white clover. C, mature asci and ascospores. After Hopkins. Pleosphaerulina Passer (p. 165) Perithecia subepidermal, erumpent, small, globoid or lenticular, black; asci 8-spored, clavate; spores muriform, hyaline; paraphyses none. 1 Hopkins, E. F. The Sphaerulina leaf spot of clover. Phytop. 13: 117, 1923. 178 PLANT DISEASE FUNGI P. briosiana Pol. Perithecia few, immersed then erumpent; asci aparaphysate, 80-90 x 30-40 /x; spores oblong -fusoid, 3-4 trans- verse septa, often with 1-2 longitudinal septa, 20-25 x 6-8 ti. The cause of a spot on alfalfa and clover. Pleosporaceae (p. 158) 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 saprophytes, although several are parasites, some of considerable importance. Key to Genera of Pleosporaceae Spores 1-celled, unappendaged, elongate, hyaline or light yellow 1. Physalospora, p. 178. Spores 2- celled. Perithecia hairy; spores hyaline or brown. 2. Venturia, p. 182. Perithecia smooth; not stromatic, spores brown Aparaphysate 3. Didymellina, p. 184. Paraphysate 4. Didymosphaeria, p. 184. Spores more than 2-celled, not muriform Spores elongate, not appendaged Spores fusoid or elongate, blunt, never filiform or separating into cells Spores 3 to many-celled, hyaline or brown Spores without thick epispore, elongate, perithecia smooth ; spores yellow or dark-brown . . 5. Leptosphaeria, p. 184. Spores filiform, often separating into cells; perithecia smooth 6. Ophiobolus, p. 186. Spores muriform, asci 8-spored, spores not appendaged Perithecia hairy 7. Pyrenophora, p. 189. Perithecia smooth 8. Pleospora, p. 188. Physalospora Niessl. Perithecia subglobose, covered, membranous or coriaceous, black, with the ostiole erumpent; asci clavate-cylindric; spores ovoid or oblong, continuous, hyaline or subhyaline; paraphyses present. PLANT DISEASE FUNGI 179 This genus contains over one hundred thirty species, a few of which are parasitic on twigs and leaves. Some species possess a Gloeosporium as the conidial form. P. cydoniae Arn. (=Sph8e- ropsis cydoniae C. & E. = Sphaeropsis malorum Pk.) Perithecia scattered, astro- mate, buried, with a short protruding, papillate ostiole, globose, 180-235 m high, 300- 400 // broad; asci usually 8- spored, paraphysate, clavate, 21-32 X 130-180 M, apex thick- ened, spores elHptical, 11-15 x 23-24 ix, hyaline to greenish- yellow. Pycnidia usually scattered, 200-300 ix, ostiolate. Co- nidiophores 8-30 /x long; spores 7-16 x 16-36 m, brown, elhpsoidal, Fig. 172. — Physalospora. Perithecia and aacus. After Winter. FiQ. 173. — P. cydoniae. Histological changes in the fruit of apple. Healthy tissue at left, diseased at right. After Hesler. usually continuous, occasionally 1 or even 3-septate. MyceHum hyaline when young, brown when old. 180 PLANT DISEASE FUNGI On apple, pear, hawthorn, quince, crab apple, peach, witch hazel, oak, on fruit leaves and branches. r^^ FiQ. 174. — Pycnidium of P. cydoniae. After Hesler. FiQ. 175. — Asci and paraphyses of P. cydoniae. After Hesler. The fungus winters as mycelium in the host tissues and as pycnospores in pycnidia. New infections are by pycnospores and usually through wounds. The species appears to consist of many biologic races. Fio. 176. — P. cydoniae, longitudinal section of a part of apple twig, showing brown deposit in woody elements and mycelium in the xylem ducts. After Hesler. The mycelium is usually intercellular and in fruit is found in advance of the pathological color changes that it causes. In PLANT DISEASE FUNGI 181 the leaves hyperplasia of the palisade and the spongy tissue re- sults. In the wood the mycelium is found in the ducts and wood parenchyma, and a brown deposit is made (Fig. 176). In super- ficial bark cankers a protective cork layer (Fig. 177) develops be- low the invaded region. Other species are on willow, strawberry, birch, chestnut, oak, fir, mulberry, elm, magnolia. Fig. 177. — -P. cydonise, showing brown deposit in medullary ray cells and phloem parenchyma. Below the diseased region is seen the cork layer. After Hesler. Venturia Cesati & de Notaris (p. 178) Perithecia superficial or erumpent, bristly, ostiolate, membra- nous, dark colored; asci sessile or short stipitafce, ovate or saccate; spores oblong to oviod elliptic, hyaline or yellowish; paraphyses usually none. The conidial stages in some cases belong to the form genus Fusicladium and consti fcute the parasitic portion of the life history of the fungus, the ascigerous form usually being limited to old or wintered parts of the host. 182 PLANT DISEASE FUNGI V. pirina Aderh. Perithecia gregarious, smooth or bristly, globoid, 120-160 ^; asci cylindric; spores unequally 2-celled, yellowish-green, 14-20 x 5-8 /x- 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 /x. It is found on the pear wintering in perithecial form on leaves, and in conidial form, or as mycelium on twigs. Fig. 178. — Mature perithecium of V. insequalis, showing mature ascospores, the method of ejection of ascospores, and the bristles that sometimes occur about the ostiole. After Wallace. V. inaequalis (Cke.) Wint. (= V. pomi [Fries] Winter) Perithecia globose, short-necked, 90-160 /x, smooth or bristly above; asci cylindric, 55-75 x 6-12 /x, without paraphyses, 8-spored; spores yellowish-green, unequally 2-celled, upper cell shorter and broader, 11-15 x 5 /x. Conidia ( = Fusicladium dendriticum) effused, velvety, forming dentritic patches of compact masses of erect closely septate, brown mycelium; conidiophores closely septate, brown, 50-60 x 4-6 /x, wavy or nodulose; conidia solitary, terminal, obclavate, yellowish- olive, continuous when young but at length septate, 12-22 x 6-9 n. Its hosts are apple and other pomaceous fruits except the pear. PLANT DISEASE FUNGI 183 The two conidial forms have l:>een 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 de- velopment is also said often to be subcuticular, resulting in a sep- aration of the cuticle from the epidermis. Fig. 179. — V. insequalis. A, portion of a section through a scab spot on apple; b, spreading under and Ufting the cuticle, a; c, partly disorganized cells of the apple; e, healthy cells of the apple. B, two conidiophores with summer spores /. C.spores germinating. After Longyear. 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. 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. Cultures from ascospores gave rise to typical conidia. Other species are found on hawthorn, cherry, birch, aspen and sorbus. 184 PLANT DISEASE FUNGI Fig. 180. — D. iridis; perithecium show ing asci and spores. After Tisdale. Didymellina v. Hohn. (p. 178) Perithecia covered, membranous, globose-depressed, minutely papillate, black; asci cylindric or clavate; spores ellipsoid or ovate, 2-celled, hyaline; paraphyses none. Like Didymella except lack- ing paraphyses. D. iridis. (Desm.) v. Hohn. Perithecia scattered, smooth, globose, dark, 130-246 ijl, subepi- dermal, ostiole papillate; asci 36-54 x 72-117 jji, no paraphyses; spores oval or elliptical, 1-septate, constricted, 10-16 X 30-54 IJL. Conidia (=Het- erosporium gracile Sacc). Conidio- phores olivaceous, crooked, 11-150 m; conidia echinulate, cylindrical, ends rounded, 2 to 3-septate, 14-19 x 40-60 ju. It causes a spot on the iris leaves. Didymosphaeria Fuckel (p. 178) Perithecia immersed, later erumpent; asci cylindric to clavate, 8-spored; spores elliptical to ovate, 2-celled, brown. This genus differs from Didymella chiefly in the dark-colored spores. It contains some one hundred twenty species and has occa- sional parasitic representatives on leaves and twigs. D. catalpae Parker 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 fx; ostiole broadly conical, erumpent; asci 8-spored, cylindrical, usually somewhat curved; paraphyses few or wanting; spores oblong-elHptical, hyaline or yellowish, uniseptate, constricted in the middle, 9.6-13 x 3-4 /i. On Catalpa. Leptosphaeria Cesati & de Notaris (p. 178) Perithecia at first subepidermal, at last more or less erumpent, subglobose to globose, coriaceo-membranous, ostiole usually papil- Fio. 181. — Didymosphaeria. C, an ascus; D, conidio- phore and conidia. Af- ter Brefeld. PLANT DISEASE FUNGI 185 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, Sporo- desmium, Septoria, 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 m; spores 1-rowed, oblong, 3-septate, constricted, fuscous, 10-15 X 3.5-4 /jl. Fig. 182. — Cross-section of raspberry bark showing two peri- thecia of L. coniothyrium at the top, A, and two pycnidia of Coniothyrium fuckeHi, at the bottom, B. 4. An ascus of L. coniothyrium. 5. Spores of L. coniothyrium. After Stewart. Pycnidia (= Coniothyrium fuckelii) superficial, scattered, dark, 180-200 iJL, globose-depressed; conidia numerous, globose to short- elliptic, 2.4-5 X 2-3.5 fjL. It occurs on black and red raspberries causing cane-blight; also as the cause of rose and apple canker and apple fruit rot. L. avenaria Weber. ^ Conidia (= Septoria avense Frank.) Pycnidia more or less scattered, often in rows, subepidermal, ^ Weber, George F. Septoria diseases of cereals, Phytop. 12: 10, 449; 1922. 186 PLANT DISEASE FUNGI globose to subglobose, 90-150 /x in diameter, ostiole slightly elevated, 20-30 ^ in diameter; spores rod-shaped, 3-septate when mature, hyaline, 3-4 x 25-45 /jl; perithecia globose to subglobose, 60-130 fjL in diameter; ostiole usually round, not protruding, 12-20 fi in diameter; asci narrowly clavate with rounded tips, hyaline, thin walled, 10-18 x 30-100 n; asci 8-spored; ascospores fusoid; 3-septate, constricted, light yellow to slightly olivaceous, 4.5-6 X 23-38 n; paraphyses cyHndrical, hyaUne, 2 x 60 ju. On oats. L. tritici (Gar.) Pass. Perithecia innate, globose, black, papillate; asci clavate, short- stipitate, 8-spored; paraphyses filiform, 48-50 x 15-16 fx; spores 2- seriate, round, fusoid, 3-septate, constricted, pale, 18-19 x 4.2-5.5. /x. Conidia ( = Ascochyta graminicola) . Pycnidiospores usually 2-celled, 12-20 x 3.5 fx. On wheat. Others are on grape, rye, sugar cane, rice, rape, clover, alfalfa, potato, beet, phlox, rhododendron. Ophiobolus Riess (p. 178) Perithecia scattered, subglobose, submembranous, covered or sub- erumpent, ostiole papillate or elon- gate; asci cylindric; spores fusi- form, hyaline or yellowish. A genus of some one hundred twenty-five species. O. cariceti (B. & Br.) Sacc.^- ^ O. graminis Sacc. Parasitic on wheat, barley, rye and various wild grasses, causing the take-all disease. The mycelium permeates the roots of the host causing them to become brittle and easily broken away and de- velops profusely above the crown Fig. 183.— Asci and spores of o. cariceti, of the plant in and about the andKiSy. '^^*'' Fitzpatrick, Thcmas j^^f ghcaths. It fomis a definite, thick plate between the inner leaf sheath and the culm; the mycelial plate usually adhering to ^ Kirby, R. S. The take-all disease of cereals and grasses. Phytop. 12: G6, 1922. 2 Fitzpatrick, H. M., Thomas, H. E., Kirby, R. S. The Ophiobolus causing take-all of wheat. Mycol. 14: 30, 1922. PLANT DISEASE FUNGI 187 the culm when the leaf sheaths are stripped away, composed of coarse, dark-brown hyphse, 3-6 ix in diameter, which frequently run parallel to one another forming broad, flat, ribbon-like strands resembling somewhat compressed rhizomorphs; perithecia mem- branaceo-carbonaceous, dark-brown to black, smooth, rostrate, ostiolate, occurring on the roots of the host, singly or in groups, the individuals in a group occasionally fused laterally but no true stro- matic tissue developed, often developed in great numbers, when young hidden from view but, at maturity the beaks protruding Fig. 184. — O. cariceti, portion of the mycelial plate formed around the culm. After Fitzpatrick et al. and prominent. The obliquely attached curved beak is so char- acteristic of the species as to be almost diagnostic. Ascigerous portion of the perithecium globose or subglobose, 330-500 n in di- ameter, narrowing gradually into the truncate-conoid to cylindrical beak; asci numerous, fascicled, elongate-clavate, straight or curved, short-stipitate to subsessile, 90-115 x 10-13 ix, rounded at the apex, 8-spored, thin-walled; paraphyses abundant, thread-like, flexuous, unbranched, hyaline; ascospores hyaline to faintly yellowish in mass, linear, curved, broader at the middle and tapering gradually toward the ends, the upper end rounded, the basal end more acute, 60-90 x 3 /i, when young, continuous and multiguttulate, at matur- 188 PLANT DISEASE FUNGI ity 5 to 7-septate, not reaching morphological maturity until late autumn or winter. Inoculations with pure cultures have produced the typical take- all disease on wheat, barle}^, rye and members of eight other grass genera. Mature perithecia were found about ten weeks after in- oculation. Pleospora Rabenhorst (p. 178) 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. Conidia occur as Macrosporium, Alternaria, Cladosporium, Sporodesmium, Phoma, Helminthosporium. There are over two hundred twenty-five species, mostly saprophytic. Many co- nidial forms whose connection to this genus have not yet been definitely proved proba])ly belong to it and are in many in- stances parasites. P. tropeoli Hals, is reported as the cause of disease of the cultivated Nas- turtium. X400 £5o Perithecia pyriform, 140-160 ^x', asci oval. Fig. 185.— Pleospora from pas- onc-sided, spores hyaline or very light- X400 sion-fruit. The spores are nlivflppniiq 9^-'\^ V fi-S n just beginning to germinate, OUVateOUb, ^O OO X U O /i. the end cells starting first. After Cobb. The Alternaria form was grown from the ascopores by Halsted and from the Alternaria spores, grown in pure culture, perithecia were obtained in about twelve days. Others are on orange, chicory, pea, tobacco, rice, carrot, elm, box-elder, hyancinth. 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 PLANT DISEASE FUGNI 189 of all of these grain Pleosporas, but recent work of Diedicke shows that one form which he regards as P. trichostoma (Fr.) Wint. possesses an Alternaria conidal form. Following Diedicke, the forms given below would be recognized. The discussion of the conidial forms is given on page 404. P. bromi Died. Perithecia brown; hairy; asci 189-288 x 34-59 /z, saccate, thin- walled; spores 2-seriate, golden-brown, 4-celled, 48-83 x 19-33 fx. Conidia (=Helminthosporium bromi) on brownish spots, 108- 150 X 13-20 fjL, 5 to 7-celled, dark colored. On Bromus. P. gramineum Died. Conidia (=Helminthosporium gramineum); conidiophores short, subflexuose, light-brown; conidia solitary, elongate-cylin- dric, 4 to 7-celled, 15- 19 M wide and of varia- ble length. On barley and rye. P. tritici- repentis Died, is found on Triti- cum repens. (Conidia = Helminthosporium tri- tici repentis.) P. trichostoma (Fr.) Wint . ( = Pyrenophora trichostoma (Fr.) Sacc.) Perithecia ffreearioUS, ^ig. ISe.— p. trichostoma. l, group of asci, 2 a single .■,■,-, 1 spore at the apex of an ascus. After Diedicke. mnate, conical, black, ostiole surrounded by black hairs, which are simple, septate, 6-8/x in circumference; asci clavate, 300 x 40 /jl; spores broadly oblong, obtuse, unequally 4 to 6-septate, muriform, brownish, 52 x 20 ^i; paraphyses branched. On rye with the conidial form = Alternaria trichostoma Died. Gnomoniaceae (p. 158) 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 over one hundred fifty species; two genera con- tain important pathogens. 190 PLANT DISEASE FUNGI Key to Genera of Gnomoniaceae Spores 1 -celled, mouth of the perithecium elongate, beak-like, straight; asci 8-spored; spores ellipsoid or fusoid; stroma present . . 1. Glomerella, p. 190. Spores 2 or more-celled; asci 8-spored; spores elongate, 2 to 4-celled 2. Gnomonia, p. 196. Glomerella Spaiilding & von Schrenk ^ 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, hya- line, oblong, 1-celled, slightly curved or straight, elliptic; pa- raphyses usually none. Conidia in part = Colletotrichum and Gloeosporium, a genetic connection first proved by Atkinson in 1898. 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 conidio- spores. This leads to great un- certainty as to specific limita- tions. The conidial forms are very common and are usually parasitic. The ascigerous stages are comparatively rare. Some- times they are found in nature; again only in artificial culture. Some forms known to be ascigerous may in one culture yield abundant perithecia while other cultures of the same fungus may persistently refuse to bear asci at all. G. cingulata (Stonem) S. & v. S. As the cause of the bitter rot of apples this fungus may be described as follows. Perithecia on decaying fruits, subspherical, more or less grouped; 6 Fig. 187. — 7, Perithecium of G. cingulata show- ing asci in situ; 6, asci showing detail. After Spaulding and von Schrenk. ^ Shear, C. L. and Wood, A. K. Studies of fungous parasites belonging to the genus Glomerella. U. S. Dept. Agr. Bur. PI. Ind. Bui. 253, 1913. PLANT DISEASE FUNGI 191 asci subclavate, fugaceous, 55-70 /z; ascospores allantoid, 12- 22 X 3-5 IX] conidial stage 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 ii. 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. The ascigerous stage was found by Clinton in 1902. 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 discoloration of cells and dissolution of their connection with neighboring cells. The mycelium is first hyaline but later, especially in the stromata, it may be quite dark. Acervuli soon appear, often in concentric rings, lifting the epidermis with their palisades of conidiophores. The latter, at first hy- aline, later olivaceous, bear the numerous conidia, which are pinkish, rarely cream- colored, in mass. In germination the co- nidia become unisep- tate and often on the tips of the young my- celium develop the dark thick-walled ir- regular shaped spore- Fio. ISS.— G. cingulata, germinating conidia. Note septa like structures so ^°^ appressoria. After Spaulding and von Schrenk. common on the sporelings of the Melanconiales, which serve as organs of attachment to aid in infection. Perithecia, which are often 4-5 mm. in diameter varying from one to many in each such stroma, appear in black knotted masses of mycelium. The asci were evanescent, disappearing soon after the spores mature. In canker formation the mycelium grows in the live bark, kill- ing it and the cambium. The cankers are thought to be compara- tively short lived, perhaps surviving only the third year. Recipro- 192 PLANT DISEASE FUNGI cal 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 mycelium hibernates in limb cankers and in mummified fruit. The fungus produces amylase, invertase, cytase and inulase acting on carbohy- drates, also emulsin, lipolytic enzymes, protease, erepsin, and amidase. From extensive cultural studies of both conidial and ascigerous material and trials by cross inoculation Shear and Wood conclude that this spe- cies is indistinguishable from fungi described under other names as follows: Glomerella psidii (Del.) Shel. on guava. Glomerella rubicola (Sto- nem.) S. & v. S. on Rubus. Glomerella rufomaculans (Berk.) S. & v. S. on apple. Colletotrichum camelliae Mass. on Camellia and tea. Colletotrichum carica Stev. and Hall on fig. Colletotrichum gloeosporioides Penz. on sweet orange and pomelo. Colletotrichum theobromicolum Del. on Theobroma. Gloeosporium cingulatum Atk. on privet. Gloeosporium fructigenum Berk, on apple. Gloeosporium ribicolum E. & E. on Ribes. Gloeosporium rubi E. & E. on Rubus. Gloeosporium ruformaculans (Berk.) Thlim. on Vitis. Lsestadia camelliae (Cke.) Berl. & Vogl. on tea. Neozimmermannia elasticae (Zimm.) Koord. on rubber plant, and that it also parasitizes quince, loquat, mango, avocado, coffee, palm, sweet pea, arrowroot, ginkgo, Gleditschia, Carya and other hosts, at least 34 all told. Varieties of the species have been described on cranberries and cyclamen. Fig. 189. — Plate culture of G. cingulata show- ing perithecia-bearing masses. After Spauld- ing and von Schrenk. PLANT DISEASE FUNGI 193 G. lindemuthianum Shear. i=Colletotrichum lindemuthianum (Sacc. & Magn.) Bri. & Cav. Perithecia as in G. cingulata. Spots subelliptic to irregular, depressed, brownish; acervuli scattered, surrounded by a few not very conspicuous black setse; conidia oblong, ends rounded, straight or curved, 13-32 x 3.5-5.3 )u; conidiophores cylindric, simple, 45-55 iJL. On the bean it attacks stems, leaves, cotyledons, or the pods, producing sunken spots of dead tissue which bear the numerous ^ntn^a(mse Canker deed Coat Starch Grains Fig. 190. — -C. lindemuthianum. Showing relation of the fungus to the tissues of the bean. To the left above is a diagram of a section across a bean pod through a canker. The drawing below is a much enlarged largely diagrammatic view of a portion of this same section. It shows how the mycelial threads of the fungus may penetrate the seed coat and enter the starchy tissue of the seed, there to remain dormant until the following season. On the left is a spore germinat- ing and penetrating the epidermis. To the right a magnified view of spores, one germinated. After Whetzel. pink acervuli. The fungus enters the host through the cuticle by an invading hypha produced by an appressorium. Once within the host cell it penetrates into other cells. The protoplasm of invaded cells is killed and turns brown soon after being attacked. As the host cells collapse the mycelium develops to form a stroma, the base of the acervulus. Perithecia have been seen only in pure cultures. It has been shown that the mycelium on the fruit may penetrate through the pericarp and into the seeds beneath and there hibernate. Biologic specialization within the species has been shown to exist. 1 Barrus, M. F. Bean anthracnose. Cornell Agr. Exp. Sta. Mem. 42, 1921. 194 PLANT DISEASE FUNGI Colletotrichum lagenarium (Pers.) E. & H. on fruit, leaves and stems of cucumbers, watermelons, squash, pumpkins aPxd citron and C. oligochaetum on cucurbits, are possibly identical with G. lindemuthianum. G. piperata (E. & E.) S. & v. S. Perithecia cespitose, thinly membranous, dark-brown, pyriform, hairy; asci clavate; spores slightly curved, elliptic, 12-18 x 4-6 n. Conidia ( = Glceosporium piperatum) on circular or oval spots; acervuli pustular, concentrically arranged, conidia 12-23 x 5-6 n. The ascigerous stage was grown from pure cultures of the conidia taken from pepper by Miss Stoneman, the perithecia appearing Fig. 191. — G. piperata, 99, perithecium external and in section. 100, asci in detail. After Stoneman. about a month after inoculation. Typical conidia were also se- cured from ascospore sowings. It is possible that this is identical with G. cingulata. G. gossypii (South.) Edg. Perithecia distinct or crowded, very abundant, covered, dark brown to black, subglobose to pyriform, 80-120 x 100-160 n, beak up to 60 fj. long; asci numerous, clavate, 55-70 x 10-14 ju; PLANT DISEASE FUNGI 195 spores elliptic, hyaline, rarely curved, 12-20 x 5-8 //; paraphyses long and slender, very abundant. Conidia ( = Colletotrichum gossypii), acervuli erumpent, conid- iophores colorless, longer than the spores, 12-28 x 5 fx; conidia irregularly oblong, hyaline or flesh-colored in mass; setae single or tufted, dark at base, color- less above, straight, rarely branched. The conidial stage of this fungus was de- scribed by Southworth and independently by Atkinson on cotton. The ascigerous stage was first seen by Shear & Wood in artificial culture. The mycelium is richly branched and septate, usually hyaline but sometimes slightly smoky. It grows between and in the host cells which are often filled with it, causing loss of chlo- rophyll, browning and collapse. Studies by Atkinson and by Barre show that in case of diseased bolls the mycelium may extend through the pericarp, sporing on its inner wall; extend thence to the seeds; penetrate and grow in them, Fig. 192, and in the cells of the lint. Barre has fiq. 192.— g. gossypii. shown that even the endosperm and cotyledons Jhow?ng°^the^°fungu3 may be invaded, Fig. 192, and spores produced penetrating the huii , 1 •! • t • 1 1 ri 1 ^^^ entering the upon them while withm the seed coats. Such young seed, spores 1 ^ ^' , J n ii i are being produced seeds and Imt may appear outwardly as though upon the outer portion perfectly normal. the*^^sur"ace^''of ""X The conidia are formed in acervuli, sub- feTfilrre!^ ^°^*' ^^" tended by stromata. Setae, from few to many increasing with age of the acervulus, are present and conidia are occasionally found on them. In germination conidia usually de- velop one, sometimes two septa and produce dark chlamydo- spores. Acervuli are common on bolls, less so and smaller on leaves and stems. The perithecia as found in the field by Edgerton in Louisiana were usually entirely embedded, with the beaks only protruding and were often numerous and crowded. The fungus has repeatedly been 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. 196 PLANT DISEASE FUNGI 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 of dehiscence of the carpels. Accord- ing to Barre, there is evidence that the fungus may destroy the con- tents of the boll before it shows upon the outside. Atkinson found that conidia five months old were alive, but that at seven months they failed to ger- minate. 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. Fig. 193. — G. gossypii, D, and E, fungus growing in cotton lint fibers. After Barre. Gnomonia Cesati & de Notaris (p. 190) Perithecia covered or erumpent, submembranous, glabrous, ostiole more or less elongate; asci ellipsoid or fusoid, apically thick- ened, opening by a pore; spores elongate, hyahne, 2 to 4-celled; paraphyses none. There are some sixty species. Fusicoccum, Myxosporium, Sporonema, Gloeosporium, Marssonina, 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. Perithecia immersed, subglobose or slightly flattened, 150- 200 iJL, short, rostrate; asci long-clavate, 48-60 x 12-15 fx, generally bent at right angles at the base, apically very thick, opening by a pore; spores 14-19 x 4-5 fx, straight or slightly curved, unequally 2-celled, the upper cell longer. Conidia variable in habitat and habit. (1) ( = Gloeosporium nervisequum) acervuli subcuticular, 100-300 /jl; conidiophores short; conidia oozing out in a creamy-white mass, hyaline, ellip- soid, 10-14 X 4-6 IJL, pointed at one end and rounded at the other. (2) ( = G. platani) acervuli subepidermal, conidiophores long; conidia as above. (3) ( = Discula platani = Myxosporium val- soideum) forming minute, subepidermal, erumpent pustules on PLANT DISEASE FUNGI 197 twigs; conidia elliptic to oblong, hyaline, 8-14 x 4-6 ^; (4) ( = Sporonema platani = Fuscicoccum veronense). Pycnidia formed on old leaves on the ground, erumpent, subcuticular, brown, 200- 300 ix; conidia numerous, oblong, ovoid to fusoid, 7-11 x 3-4 ix. 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 surrounding tissue. A stroma Fig. 194. — G. veneta, perithecium. After EdgertoD. Fig. 195. — G. veneta, asci and spores. After Ed- gerton. is formed on the outer layers of the mesophyll and from this arise the short conidiophores to constitute the acervulus. The ascigerous form was first found by Klebahn on old leaves on which it matures about Christmas time. 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. tilmea (Schw.) Thiim.^ Perithecia subspherical, 250-300 ijl broad, 150-200 /x deep, os- tiole 100 ii long, 75 wide; asci 8-spored, aparaphysate, oblong, 45-55 X 9-11 ju; spores hyaline, unequally 2-celled, with a septum near the lower end, 8-10 x 3-3.5 At, small cell 2 ^. Conidia (=Gloeosporium ulmeum Miles). Acervuli somewhat gregarious, often confluent, borne on black stromata, usually over the base of the developing perithecium, covered by the darkened cuticle which later splits and cracks irregularly and finally breaks away entirely, subrotund or irregular, averaging 500 ijl in diameter, but often as large as 800 //, usually epiphyllous; conidiophores 1 Miles, L. E. Leafspots of the elm. Bot. Gaz. 71: 161, 1921. 198 PLANT DISEASE FUNGI cylindrical, crowded, 8-12 x 1.5-2 fj,, temiinating in a threadlike projection on which the spores are borne; conidia elongate-oblong or cylindric, bacillar, pointed at one or both ends, straight or very slightly curved, hyaline, 1-celled, 8-10 x 2-2.5 fi, when freshly collected extruded in small white masses. The disease caused on various species of elm appears first in spring as small whitish or yellowish flecks on the upper side of the leaf soon after it unfolds. Black specks soon develop in this area Fig. 196. — Two porithecia of G. ulmea in nearly mature condition. After Miles. and by coalescence often form large (0.5-3 mm.), coal black spots, due to a stroma-like subcuticular structure. In June the perithe- cia here form, completing development in the following March. The connection between the conidial and ascigerous stages was demonstrated by inoculations. G. leptostyla (Fr.) Ces. & d. Not. Perithecia conic, short-beaked; asci subclavate, 45-65 x 10-12 m; spores fusoid, curved, 18-22 x 4 ^u, hyaline. Conidial phase = Marssonina juglandis. Acervuli gregarious, hypophyllous, rounded; conidia obovoid, 8-10 x 4-5 fi, 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 PLANT DISEASE FUNGI 199 infection. Tlie conidial form is common on walnut leaves, also especially severe on the butternut, often defoliating this host in midsummer. Other species are recorded on cherry, blackberry, rice, oak. Valsaceae (p. 158) 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 of Valsaceae Spores 1-celled, ellipsoid, with a hyaline mem- brane 1. Valsa, p. 199. Spores 2 to 4-celled, with cross walls only, hy- aline, ellipsoid or fusoid 2. Diaporthe, p. 200. Valsa Fries 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 hyaline or light-brown; Fig. 197. — Valsa. a, habit sketch; B, perithecia; C. asci. , After Tulasne. paraphyses none. V. leucostoma (Pers.) Fr. Stroma strongly convex, 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 /z. Conidia (=Cytospora rubescens); stromate, erumpent, reddish; conidia allantoid, 4 fx. On pome and stone fruits causing ^'dieback" of twigs, and canker of limbs. On twigs infection often takes place through the buds. Diseased twigs show the mycelium matted in the cambium region. Other species are on apple, plum, Ficus, cacao, Alnus, and Hevea. 200 PLANT DISEASE FUNGI Diaporthe Nitschke (p. 199) Stroma variable, usually definite; perithecia membranous sub- coriaceous, generally pale-cinereous within, with a cylindric or filiform beak; asci fusoid; spores fusoid to subelliptic, 2-celled, hyaline, appendaged or not; paraphyses none. Conidia=Phoma, Cytospora, etc. D. taleola (Fr.) Sacc. Stroma cortical, definite, depressed, pulvinate, 2^ mm., cov- ered; perithecia few, 4-10, buried, their ostioles converging, erum- Fio. 198. — Valsa leucostoma. Cross-section of a Fig. 199. — Diaporthe. B, stroma, in sec- pycnidium showing locules. After Stevens. tion; C, asci. After Tulasne. pent in a small light-colored disk; asci cylindric, 120-140 x 10-12 /z, spores elliptic, uniseptate, constricted, with setaceous appendages, 15-22 X 8-9 M- It causes canker on oak, killing the cortex over large areas. A year later the cushion-like stromata appear. The mycelium pene- trates both wood and bark, probablv entering through wounds. D. batatatis (E. & H.) Harter & Field.^ Stromata valsoid, immersed, erumpent, carbonaceous, with ^ Harter, L. L. & Field, E. C. Sweet potato storage-rots. Jour. Agr. Res. 15: 337, 1918. PLANT DISEASE FUNGI 201 exserted beaks 0.5-3 mm. long; perithecia 9-25, immersed, 120- 370 M broad; asci aparaphysate, 8-spored, 25-38 x 7-12 /x; spores subelliptical, hyaline, 1-septate, constricted, 8-12 x 4-6 ^l. Pycnidia ( = Phoma batatae) black, ostiolate, with irregular cavity; spores oblong-fusoid, 6-8 x 3-5 tx, continuous, hyaline; conidiophores filiform; stylospores in same or separate pycnidia. Fig. 200. — Crypto- sporella viticola. Fusicoccum stage from mummied grape. After Gregory. Fig. 201. — C. viticola portion of a pycnidium showing conidiophores, conidia and scolecospores. After Shear. In roots, stems and leaves of sweet potato. Ascigerous stage seen only in culture. The contents of the cells turn brown and the whole potato becomes dry and powdery. D. umbrina Jenk. Pycnidia subglobose to lens-shaped; pycnospores subfusoid, straight or slightly curved, hyaline, 5-11 x 2-3 /i; sporophores simple or branched, tapering above, 12-40 ix in length; perithecia, two to five, immersed in a valsoid stroma, globose, with beak scarcely projecting above the epidermis, 110-290 ^i in diameter; beaks 150-195 /i in length; asci clavate, subsessile, aparaphysate, 30-50 X 6-8 ix; spores elliptical, usually hyahne, when mature sometimes light to olivaceous, continuous or sometimes with one pseudo-septum, 8-11 x 3-4 yi. It forms cankers on the stems of cultivated roses. 202 PLANT DISEASE FUNGI D. phaseolarum (C. & E.) Sacc.^ ( = Phoma subcircinata E. & E.). Perithecia gregarious, 158-355 /x, buried, ostiole protruding; asci 28-46 x 58 /jl, spores oblong-lanceolate, 6-12 x 2-4 /x; pycnidia 158-475 fx in diameter; spores hyaline, oblong or fusoid, 1-celled, 6-9 X 2-4 jLi; stylospores present or absent, slender, hyaline, 12- 31 X 1.5-2 M- This fungus causes spots in leaves, pods and stems of Lima beans. The life history and connection of the various morpho- logical forms have been made from study of single-spore cultures. Wounds are not necessary to infection, the entrance being stomatal. Other species of this genus are on pear, hop, dogwood, fir, rose. Melanconidaceae (p. 158) A small family of about two hundred species. Stroma pulvinate, sunken; perithecia sunken in the stroma, the mouth erumpent; asci cylindric or clavate; paraphyses present. Cryptosporella Tulasne Stroma valsoid, pustuliform, covered; perithecia embedded, HuJnpPtny. dA Fig. 202. — C. anomala. 31, stroma and perithecia; 32, an ascus; 33, spores. After Humphrey. Fig. 203. — Crypto- sporella viticola. Asci and paraphy- ses. After Shear. 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 ^ Harter, L. L. Podblight of the Lima bean caused by Diaporthe phaseolarum. Jour. Agr. Res. 11: 473, 1917. PLANT DISEASE FUNGI 203 and generally having a thin, black crust beneath them, disk con- vex or slightly depressed, cinerous to black; perithecia black; crowded, deeply embedded in the stroma, often elongate, ostioles scattered, asci short, broad, fugaceous; spores 7-8 jx. hyaline, elliptic, simple. On hazel and filbert causing the destruction of the tree tops. C. viticola (Red.) Sh. Pycnidia (=Fusicoccum) with labyrinthiform chambers, os- tiolate but frequently rupturing. Spores hyaline, continuous, of two fornis in the same cavity: 1. subfusoid, 7.5 x 2-5 /x; 2. long, slender, curved, 18-30 x 1-1.5 )u; perithecia buried in irregular pulvinate stromata, beak exserted; asci 60-72 x 7-8 ix', paraphyses slender, septate, wavy; ascospores subelliptic, hyaline, continuous, 11-15 X 4-6 II. Fig. 203. The conidial stage was described by Reddick as the cause of necrosis of grape vines. 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. Calosphaeria. Tulasne Perithecia astromate, free or on the inner bark, scattered or clustered, ostiole more or less elongate; asci clavate. fasciculate; spores small, cylindric, curved, hyaline, contin- uous; paraphyses longer than the asci, stout lanceo- late, evanescent. C. princeps Tul. Perithecia on the inner bark in orbicular or elliptic groups, generally densely crowded, globose, smooth and shining, necks long, Fig. 204.— Calosphaena princeps. A, group of peri- T Tin thecia; B, conidial stroma. After Tulasne. decumbent, liexuose, cy- lindric, erumpent; asci 12-26 x 4 /z; spores 5-6 x 1-5 /x. On plum, cherry, peach and even pomaceous trees. Melogrammataceae (p. 158) Stroma usually pulvinate, rarely effused, hemispheric, subperid- ial then erumpent and more or less superficial; perithecia sunken 204 PLANT DISEASE FUNGI in the stroma; conidia occur in acervuli on the surface of the young stromata or in pycnidia. A family of over one hundred twenty-five species. Key to Genera of Melogrammataceae Spores 1-celled, ellipsoid or ovate, asci clavate. .1. Botryosphaeria, p. 204. Spores 2-celled, with cross walls only, hyaline; paraphyses present; perithecia long-beaked. 2. Endothia, p. 205. 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, ostiole inconspicuous, papilliform; asci clavate; spores elliptic to oval, hyaline, continuous; paraphyses present. B. ribis G. & Dug. Stromata black, more or less pulvinate, outer surface botryose, 1^ mm. in diameter, usually 2-3 mm., and surrounded by the fissured periderm, regularly scattered or in more or less definite, longitudinal rows or elongated stromata. Perithecia somewhat top- shaped, with papillate os- tioles and usually project- ing, sometimes practically superficial, few to many in a stroma and usuallv interspersed among pyc- nidia, 175-250 jjL in width. Asci clavate, 80-120 x 17- 20 /x, and with numerous filiform paraphyses. Spores fusoid, continuous, hyaline, 16-23 X 5-7 /x. Pycnidia of the compound stylosporic form, Dothiorella, are borne in the same or similar stromata; spores fusoid, continuous, hyaline, 18-31 x 4.5-8 /x. Pycnidia of the simple stylosporic form, Macrophoma, are embedded in the outer bark under the much- raised primary cortex of young shoots, depressed globular, 175- 250 ju wide; spores fusoid, hyaline, continuous, 16-25 x 4.5-7.5 /x. The cause of a blight of canes of currants. £ c. Fig. 205. — Botryosphseria. B, stroma in section; C, part of perithecium and pycnidium in section. Af- ter Tulasne. PLANT DISEASE FUNGI 205 Extensive inoculation experiments and pure culture studies have definitely established pathogenicity. B. berengeriana de Not. Stromata erumpent-superficial, pulvinate; asci 70-80 x IS fj,, paraphyses filiform; spores 20-25 x 10-12 n, hyaline. On pecan causing die-back of twigs and limbs. B. fuliginosa (M. & N.) E. &. E. is the cause of a minor disease of cotton bolls. A pycnidial stage of it is a Macrophoma. Pycnidia black, 110-200 x 120-140 fx; spores 14-33 x 7-10 fx; perithecia 190-360 X 250-320 fx; ascospores 20-27 x 10-16 fx. B. marconii (Cav.) Charles and Jenkins ^ Perithecia globose, perforate, 140-160 fx in diameter; conidio- phores of the microconidia mostly dichotomously branched, septate, hyaline; microconidia polymorphic, ovate, elliptical, or terete, continuous, hyaline, 4-5.5 x 1.5-2 fx; macroconidia fusi- form or ellipsoid, continuous, hyaline, 16-18 x 5-6 jx; co- nidiophores of macroconidia slender, generally 12-15 /x in length; asci clavate, 8- spored, 80-90 x 13-15 fx; paraphyses filiform; spores fusoid, hyaline to pale green, 16-18 X 7-8 fx; microconidia, macroconidia, and asci pro- duced in the same perithe- cium. On hemp causing wilting and drooping of the leaves. The fungus also at- tacks the outer ends of the branches. Endothia Fries (p. 204) Stroma valsoid, covered, then erumpent ; perithecia with long ostioles; asci 8-spored; spores 2-celled, hyaline. ^ Charles, V. K. and Jenkins, A. E. A fungous disease of hemp. Jour. Agr. Res 3: 81, 1914. Fig. 206. — E. parasitica: section of a stroma show- ing perithecia with long ostioles. After Ander- son and Rankin. 206 PLANT DISEASE FUNGI E. parasitica (Murr.) And. & And. Stromata orange, later reddish-brown, erumpent. On smooth bark 2.4 x 1.2 mm; on rough bark coalescing in the crevices to stromata several centi- meters long; pycnidia on smooth bark, globose, solitary, astro- mate; conidiophores 20-40 x 1.5 /x, simple or branched; spores hyaline, sticky, issuing in cirri, 1.3 x 3.5 /x, oblong to cylindrical. Older pycnidia in stromata irregular or labyrynthif orm ; perithecia Fio. 208. — E. parasitica: section of wall of a pycnidium show- ing conidia and conidiophores. After Anderson & Rankin. Fig. 207. — E. parasitica: section of a stroma showing pycnidium of irregular shape. After Anderson and Rankin. Fig. 209. — E. parasitica: asci and ascospores. After An- derson & Rankin. 12-40 in a stroma, 350-400 fx wide, deeply buried, with an ostiole of a length 4-6 times the diameter of the perithecium; asci 8-spored, average size 51 x 9 /i; spores oblong to,oval, 2-celled, constricted, 4.5 X 8.6 /x; mycelium 1.5-12 fx thick, yellow, due to an alcohol-soluble pigment, forming fan-like mats in the diseased bark. Parasitic on chestnut causing bark cankers, and saprophytic on oak, sumac, maple, hickory. Inoculation by mycelium gives positive results PLANT DISEASE FUNGI 207 in about 2 weeks, spores 3-5 weeks, and it appears that a wound is necessary. After attaining vigor on wounded" cells the mycelium pushes en masse, not singly, into the living bark tissue. All walls of more or less pure cellulose, except medullary rays, are destroyed and replaced by mycelium. The destruction of various bark tissues is largely attributed to mechanical action. Xylariaceae (p. 158) 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. Key to Genera of Xylariaceae Stroma encrusted, shield-form, globose or hemispheric, without a sterile base; conidial layer beneath the surface of the stroma, erumpent 1. Nummularia, p. 207. Stroma erect, simple or branched, clavate or cylindric, with a sterile base 2. Xylaria, p. 210. Nummularia Tulasne Stroma orbicular, cupulate or discoid, becoming black, mar- ginate; perithecia monostichous, peripheral, immersed; asci cy- lindric; spores subelliptic, continuous, dark. N. discreta (Schw.) Tul. Stroma erumpent, orbicular, 2-4 mm., cupulate, with a thick raised margin. Perithecia ovate, cylindric, nearly 1 mm. long, abruptly contracted above into a short neck; asci 8-spored, 110- 180 X 10-15 m; spores subglobose, nearly hyaline, then opaque, 10-12 X 13-16 ^t; paraphyses filiform, shorfc and branched. Co- nidiophores arise from the stromata; conidia oval, acute at base, 5 X 8 iu. This fungus, usually a saprophyte, is a serious parasite on the apple. 208 PLANT DISEASE FUNGI The mycelium grows first in the wood attacking the paren- chyma cells and medullary rays, proceeding to the bark after the underlying tissues have been killed. From July to Sep- tember the stromata, 3-5 mm. in diameter, appear in the bark :-. ^ :; 0 0 D Fio. 210. — N. discreta. B, stroma and perithoria, C, a perithe- cium, D, asci. After Hasselbring. and bear conidia in the fall or early spring. The perithecia de- velop during the second or succeeding years. Infection occurs only through wounds. In living tissue the mycelium advances chiefly through the ducts and medullary rays. Cells are killed several centimeters distant from the fungus. The mycelial advance is faster in old, e. g., 4-year old wood, than in younger wood. PLANT DISEASE FUNGI 209 Fig. 211. — N. discreta, section of a stroma with ascospores within and conidia on the surface. After Cooper. f> ^J 0 o Fig. 212. — N. discreta, asci and asco- spores. After Cooper. Fig. 213. — N. discreta, cross section of apple wood showing mycelium. After Cooper. 210 PLANT DISEASE FUNGI Xylaria Hill (p 207) Stromata erect, corky or woody, simple or branched, black, with sterile stalk; perithecia in the upper parts of the stroma; asci 8-spored; spores 1-celled, black. X. hypoxylon (L.) Grev. A root rot of apple trees is due to a fungus closely related to the above named species, perhaps identical with it. X. polymorpha and X. digitata are also reported in similar connection. Roots of affected trees are covered with a thin, white, compact, mycelial growth which soon develops into a black stroma. Black, anastomosing rhizomorphs radiate from the stroma several centimeters along the root; the cortex below is disintegrated and distal parts of the root die. The myceUum extends also into the wood, turning it brown. BASIDIOMYCETES (p. 56) The basidium is the dis- tinguishing character of this class. It is typically a sporo- phore bearing short stalks on its distal end, the sterig- mata, usually four, on which are borne spores, basidio- spores, one on the tip of each sterigma, Fig. 214. In the great majority of genera the basidia are typi- cal and are clearly recog- nizable as such. In many of the lower basidiomycetes the basidia deviate somewhat from the typical form. Thus in the Hemibasidii, the smut fungi, Fio. 214.— The typical basidium with sterigmata the basidia are not typical TiLTBlry": '''^'""' ''""" °' development. .^ ^^^^ ^^^^ ^^^^^^ ^^^.^^ from chlamydospores, not directly from the mycelium. Figs. 216, 226, and that they may produce more than the normal number of four sporidia and these PLANT DISEASE FUNGI 211 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. Pecuhar cell connections known as clamp connections, or knee joints, Fig. 218, are often found. The basidia in many genera are borne on large complex sporophores composed of the mycelial threads interwoven to form a false parenchyma. The spores may germinate by tubes or by budding. Typical sexuality seems entirely wanting, even rudimentary or vestigial sexual organs, certainly recognizable, have not been found. The group is supposed in this regard, to represent the results of extreme simplification; the sexual organs to have long ago disappeared and the simple nuclear fusions that now exist to serve functionally as fertilization. Key to the Subclasses of Basidiomycetes Chlamydospores at maturity free in a sorus, produced intercalary, from the mycelium; basidiospores borne on a promycelium and simulating conidia 1. Hemibasidii, p. 211. Chlamydospores absent or when present borne on definite stalks Basidia septate, arising from a resting spore or borne directly on a hymenium 2. Protobasidii, p. 230. Basidia nonseptate, borne on a hymenium . . 3. Eubasidii, p. 280. Hemibasidii The Hemibasidii contain one order. Ustilaginales ^ Parasitic fungi, smut producers, mycelium consisting of hyaline, somewhat septate, branched, mostly intercellular filaments, prac- tically limited fco the interior of the host; at maturity often disap- pearing partially or wholly through gelatinization ; fertile mycelium compacting into masses and giving rise to numerous chlamydo- spores formed from its contents. Sporidia rarely develop on the ^ Clinton, G. P. North American Flora, 7: pt. 1 Ustilaginales. N. Y. Bot. Gard, 1906. 212 PLANT DISEASE FUNGI 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 com- » posed in part of sterile cells. The Ustilaginales are all para- sites on higher flowering plants. The vegetative mycelium is mostly inconspicuous and is often distrib- uted very widely in the host plant without giving external evidence of its presence until time of spore Fig. 215.— Ustilago spores showing devel- formation. It Seuds VarioUsly opment. After de Bary. ^^^^^^ botryOSe Or SphcHCal haUS- toria 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. Fig. 21G. — Ustilago. 2, promycelium with nucleus in mitosis; 5, with 4 nuclei; G, with sporidia. After Harper. The chlamydospores develop directly from the vegetative my- ceUum; new and numerous transverse cell-walls are formed; the resulting short cells swell, round off and become coated with a gel- atinous envelope. This later disappears and the spores develop a new, thick, usually dark, double wall which is variously marked. The chlamydospores may be simple or compound, fertile or in PLANT DISEASE FUXGI 213 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 families, Figs. 216, 226. From the promycelium of most species there develop spor- idia, often called conidia, 1-12 or even more. The promycelium is regarded as homologous with the basidium of the other basidio- mycetes and the sporidia as basidiospores. The sporidia in suitable nutrient solutions often undergo re- peated and indefinite budding closely simulating yeast cells in appearance. Fusion of sporidia is not uncommon. Fig. 217. Sporidia finding lodgment in suitable plant parts under suitable environmental conditions give rise to infection. The points at which infection can occur are very diverse with different species and will be considered under the sepa- rate species below. The vegetative cells are binucleate in Tilletia, multinucleate in the Ustilaginaceae. The young chlamyd- ospores in the case of Doassansia, Entyloma, Ustilago and Urocystis are binucleate. These two nuclei, according to Dangeard, later fuse rendering the mature spore uninu- cleate. In germination the one nucleus passes into the promy- ceUum, then divides mitotically, Fig. 216, 2. A second division gives four nuclei (Fig. 216, 5) the spore nuclei. In the fusions of salsify smut sporidia, Federly has found an accompanying nuclear fusion, while Lutman finds similar fusion in the conjugating promycelial 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. Key to Families of Ustilaginales Promycelium usually with sporidia lateral at septa 1. Ustilaginaceae, p. 214. Promycelium with clustered terminal sporidia. 2. Tilletiaceae, p. 222. WJ 1 Fig. 217. — Ustilago. 17, sporidia fus- ing; 19, promycelial cells with fusion tube, apical cell disorganizing. Af- ter Harper. 214 PLANT DISEASE FUNGI Ustilaginaceae (p. 213) 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 With false membrane of definite fungous cells 1. Ustilago, p. 214. 2. Sphacelotheca, p. 220. Ustilago (Persoon) Roussel 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-fashion. About two hundred species, seventy-two of which are given by Clinton as occurring in America. U. avense (Pers.) Jens. Sori in spikelets, rarely in leaves, forming a dusty, olive-brown spore-mass, about 6-12 mm. long by half as wide, usually rather completely destroying floral parts, eventually becoming dis- sipated; spores lighter colored on one side, sub- spherical to spherical though often elongate, minutely echinulate, 5-9 fx in length. Wide- spread on oats. The fungus was known by the name Ustilago as early as 1552 and was called U. avense in 1591. Fig. 218.— u. avense, The specics of Ustilago ou oats, wheat and bar- germinating in water. , . , i • i , • i , -i t i i After Clinton. ley wcrc considcrcd 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 accom- plished by germ tubes from sporidia and that plants are free from PLANT DISEASE FUNGI 215 infection after the growing leaves have pushed one centimeter through the sheath leaf. The mycelium, after infection, 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 hyphse. Germination occurs readily in water, a well developed promyce- Hum resulting in about twenty-four hours, Fig. 218. The sporidia are mostly narrowly elliptical. Fusion of sporidia is common. The promycelia are usually four-celled and occasionally branch, especially near the base. U. crameri Korn. Sori in the spikelets, infecting all of the spike, ovate, about 2- 4 mm. in length, chiefly destroying inner and basal parts; spores reddish-brown, chiefly ovoid to sub- spherical though oc- casionally more elon- gate and irregular, smooth, with usually pitted contents, chiefly 8-11 /x in length. The promycelium is much branched but no sporidia are produced. The smut commonly affects the ovaries of Panicum and Setaria. U. crus-galli T. & E. 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 fjL in length. Fio. 219. — Growing point of the stem of barley, much en- larged, showing smut mycelium. After Hecke. 216 PLANT DISEASE FUNGI On Panicum crus-galli. U. sacchari Rab. Spore-mass black, spores globose or angularly globose, 8-18 /z in diameter, olive-brown or rufous, epispore thick, smooth. On sugar-cane throughout the tropics, especially in the old world. 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 transparent basal parts of the glumes; spores lighter colored on one side, usually subspherical or spherical, smooth, 5-9 //, the most elongate rarely 9-11 /z in length. Common on barley. This was first recognized as distinct from the oat smut in 1591 by Lobelius. 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. Sori in spikelets, forming a black-brown, adhering spore-mass sometimes small and entirely concealed by the glumes, but usually evident and destroying inner and basal parts; spores lighter col- ored on one side, subspherical to spherical or rarely elongate, smooth, 5-9 fx, the most elongate rarely 11 m in length. On oats, probably 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. U. 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 rupturing and disclosing black-brown, dusty lines of spores; spores medium to dark reddish-brown, chiefly ovoid to spherical or occasionally somewhat irregular and elongate, coarsely verrucose, at circumference usually showing the projections as tinted, blunt, scale-like appendages, sometimes even semi-reticu- late, 12-19 fjL in length. On various species of Agropyron. U. nuda (Jens.) K. & S. 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 ])ecomes dissipated leaving the naked rachis PLANT DISEASE FUNGI 217 Fig. 220.— U. le- vis, germination in modified Cohn's solution. After Clinton. behind; spores lighter colored on one side, minutely echinulate, siibspherical to spherical or occasionally elongate, 5-9 /x in length. 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, except the awn and rachis, is entirely transformed into smut. In water and in nutrient solutions the spores germinate by a single promy- celium, 1 to 3-septate, and often branched, but with- out sporidia. That infection is floral in loose smut of both wheat and barley was first shown by Mad- dox. The mycelium 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 sections by Lang. The embryo was reached by the mycelium some four weeks after infection of the pistil. In resting grains the mycelium 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 infection 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 down on pedicels, oblong, about 3-8 mm. in length, with dusty, olive-brown spore masses; myce- lium perennial in perennial parts of host; spores chiefly subspher- ical, occasionally ovate to ellipsoidal, usually lighter colored on one side, more or less minutely echinulate, especially on the lighter side, 5-8 fj, in length. On the tall oat grass. U. tritici (Pers.) Rost. • Sori in spikelets, forming a dusty, olive-brown spore-mass, about 8-12 mm. long by half as wide, usually entirely destroying floral parts, and eventually becoming dissipated and leaving behind only 218 PLANT DISEASE FUNGI 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 wherever cultivated. The smut mass is covered at first by a very delicate membrane. Infection is floral as de- scribed 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 promycelium branches profusely but sporidia are few or are entirely absent. U. zeae (Beck.) Ung. Sori on any part of the corn plant, usually prominent, forming irregular swellings from a few millimeters to over a decimeter in diameter, at first protected by a sort of false, white membrane composed of host 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 ii, the most elongate 15 /u in length. Fio. 221. — U. tritici, germination in mod- ified Cohn's solution. After Kellerman and Swingle. Fig. 222. — U. zese, stages in spore development. After Knowles. The germination of the spores, which occurs but poorly in water, was first studied by Klihn in 1857 and in 1874 he saw the penetration of the germ tubes through the epidermis of the corn plant. Bre- feld showed that the spores germinate well in nutrient solutions and that secondary spores are formed; also that corn can be in- fected by the sporidia at any point on its surface above ground when the tissues are soft and actively growing; and that infection is local on the host. PLANT DISEASE FUNGI 219 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 chlamydospores produce conidia in the air freely. It is these, air-borne, arising from spores on the ground, manure, etc., which are chiefly responsible for infection. They must reach the plant on a susceptible part and under suitable conditions of mois- ture. The germ tubes from the sporidia pen- etrate the epidermis, grow through or be- tween the cells. Fig. 222, with an irregular mycelium which branches profusely and calls forth great hypertrophy of the surrounding host tis- sue. In sporing, the mycelium forms a great number of short, slender, irreg- ular branches which make up a close tan- gled network in the diseased tissue. These slender branches swell, gelatinize, and fiq. 22.3 portions of them round off as spores. Fig. 222. U. striaeformis (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 ruptured and dusty brown to black, linear masses of spores be- come scattered and the leaves become shredded; spores usually ellipsoidal to spherical, occasionally irregular, prominently echinu- late, chiefly 9-14 /x in length. _. U. zeae. 1, germination after three days in water; 2, similar but in air, showing air sporidia. After Clinton. 220 PLANT DISEASE FUNGI It appears to be perennial. The spores germinate sparsely. The promycelium is long, branched, septate, and produces no sporidia. On red top, timothy and species of Poa and Festuca. Other economic species of less import in America are in sor- ghum, barley, Panicum, bamboo, Tragopogon, tulip. Sphacelotheca de Bary (p. 214) Sori usually in the inflorescence, often limited to the ovaries, provided with a definite, more or less temporary, false membrane, ^H 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 fun- gous cells which are hyaline or slightly tinted, oblong to spheri- cal and usually more or less firmly bound together; spores single, usually reddish-brown, developed in a somewhat centripetal man- ner as in Cintractia, small to me- dium in size; germination as in Ustilago. Sixteen species are recorded by Clinton for America. Of these only three are of economic im- portance. By Lindau the genus is not separated from Ustilago. Sphacelotheca sorghi (Lk.) CI. Sori usually in the ovaries or stamens forming oblong to ovate bodies 3-12 mm. in length, rarely fusing the very young spikelets W.^U^, ^«:.f^^fl'.-o-"?'- ydi'-< --C Fig. 224. -S. sorghi, cross section through base of young infected body (ovary). a, false membrane of epidermal cells and sterile mycelium, b, mature spores, b', im- mature spores, c, columella. After Clin- [^^q irregular forms, protected for ton. some time by a false membrane upon the rupture of which the olive-brown spore-mass becomes scattered, leaving naked the distinct columella of plant tissue. The sterile cells of the membrane break up to some extent into groups, hyaline, oblong to subspherical, chiefly 7-18 ju in length; PLANT DISEASE FUNGI 221 spores subspherical to spherical, smooth, contents often granular, 5.5-8.5 At in diameter. On Johnson grass and sorghum throughout the world. The young pistil and usually the stamens as well are displaced by the fungous mycelium, the two being often blended together. The spores germinate readily in water, either when fresh or a year old, showing papillae in from three to ten hours. The promycelium is 2 to 3-septate and from the ends of one or more of its cells nar- row tubes appear. These later fuse with the adjacent cell, forming the ''buckle joints." Either infection tubes or sporidia may also Fig. 225. — S. reiliana, longitudinal section of a growing point showing position of hyphse. After Gilbert and Potter. arise from the promycelium. Infection is possible only with young plants. The mycelium in the host plant grows rapidly into long irregu- lar, hyaline, thin-walled threads 2-4 mm. thick, which run through and between the cells. It is most abundant in the parenchyma, advancing especially through the pith region with the growth of the host. The young ovaries and stamens are eventually reached and the mycelium there develops richly under the epidermis. The outer cells remain sterile and constitute the membrane; the inner gelatinize and develop into spores. 222 PLANT DISEASE FUNGI S. reiliana (Klihn) Cl.^ Sori very prominent forming irregular masses including more or less of the entire panicle, usually 5-15 cm. in length; often at first protected by the leaf-sheath. A whitish, false membrane encloses the black-brown spore-mass and the ray-like remains of the pe- duncles or columellas. In time it becomes ruptured and the spores scattered. Sterile cells are also scattered in groups through the spore-mass, chiefly subspherical, 7-15 ix in diameter; spores some- what opaque, chiefly subspherical to spherical or occasionally ovoid or slightly angled, minutely but abundantly verruculose, 9-14 iJL in length. This is a cosmopolitan but comparatively rare form on corn, affecting the ovaries. It occurs also on sorghum. In germination a 3 to 4-celled, often branched, promycelium is formed and sporidia are produced. The host is infected while young, but not from seed borne spores, and the disease is systemic, the lateral buds carrying the infection in their meristematic tissue. S. diplospora (E. & E.) CI. is found on Panicum crus-galli and related grasses in the lower Mississippi Valley. Tilletiaceae (p. 213) Sori either forming dusty, erumpent spore-masses or perma- nently embedded in the tissues. Germination by means of a short promycelium which usually gives rise to a terminal cluster of elongate sporidia, that, with or without fusing in pairs, produce similar or dissimilar secondary sporidia or germinate directly into infection threads. The American Tilletiacese embrace nine genera and about one hundred twenty-five species. Key to Genera of Tilletiaceae Spores single Sori dusty at maturity; spores without a conspicuous hyaline appendage 1. Tilletia, p. 223. Sori permanently embedded in the tissues, definite, small 2. Entyloma, p. 229. Spores in balls Sori dusty; spore-balls with sterile cortex. ... 3 Urocystis, p. 225. Sori rather permanently embedded in tis- sues, spore-balls with sterile cortex 4. Doassansia, p. 230. ^Potter, A. A. Head smut of sorghum and maize. Jour. Agr. Res. 2: 339, 1914. PLANT DISEASE FUNGI 223 Tilletia Tulasne (p. 222) Sori in various parts of the host, usually in the ovary, forming dusty spore-masses; spores single and usually foraied singly in the ends of the mycelial threads which disappear more or less completely through gelatinization, germination usually by a short promycelium which bears a terminal cluster of elongate sporidia that in nutrient solutions, with or without fusing in pairs, may give rise to a considerable mycelium bearing secondary air-sporidia. The genus closely resembles Ustilago except in its larger spores and mode of germination. Twenty-two American species are listed by Clinton. Only four are of economic importance. T. laevis Klihn Sori in ovaries, ovate or oblong, 5-8 mm. in length, more or less concealed by the glumes, all or only part of the ovaries of a spike infected; spores ligth to dark- brown, oblong to chiefly subspherical or spherical, occasionally somewhat angular, foetid, especially when young, smooth, chiefly 16-22 /jl, the most elongate rarely 28 /j. in length. On wheat wherever grown. Infection occurs as in oats in the very young plants. From the infection point the mycelium approaches the growing point and follows the development of its host, sending its branches into each spikelet and finally into the growing ovules. Here it develops a close knot and in the ends of the threads and in the short branches the spores form. The spores germinate by a rather long, continuous, thick promycelium on the tip of which a crown of long slender sporidia develops. The sporidia soon become arched and often fuse in pairs; they develop infection threads. T. tritici (Bjerk.) Wint. Sori in ovaries, ovate to oblong, 5-8 mm. in length, more or less concealed by the glumes; sterile cells few, hyaline, sub-spherical, Fig. 226.— T. Isevis. A, germi- nating spore producing spo- ridia; B, Sporidia which have united. One has produced a secondary sporidium at x and this is sending out an infec- tion thread. After Freeman and Stedman. 224 PLANT DISEASE FUxNGI with medium-thin wall, smaller than the fertile cells, which are chiefly subspherical, light to dark-brown, with winged reticulations about 1 M high by 2-4 /x wide, and are 16-22 /x in diameter. Common on wheat, occasional on rye. Experiments have shown this to be distinct from T. Isevis which it closely resembles except for its reticulate spores. T. texana Long Sori in ovaries, ovoid or oblong, about 3-5 mm. in length, more or less hidden by enveloping glumes, forming a somewhat agglu- Fio. 227. — Tilletia tritici. A, Two spores germinated in moist air, pro- mycelium and sporidia, several of which have fused in pairs. Second- ary sporidiaat C. B, Spores germinated in water, promycelia elon- gate, septate. The protoplasm passes over into the younger celb. After Tubeuf. tinated, light-reddish-brown spore-mass; sterile cells not very numerous, hyaline, with very thick, often lamellate walls; fertile cells very light colored, orange-yellow appearing as if imma- ture, chiefly subspherical or spherical, with prominent conical tubercles which extend out 2-3 ju, chiefly 19-25 ix in diameter, in- cluding envelope. On Hordeum nodosum in Texas. T. horrida Tak. Sori in the ovaries more or less destroying them, completely concealed by enveloping glumes; spores usually present in different stages of development, the mature spores almost opaque, chiefly subspherical to spherical, with very coarse hyaline or slightly tinted, somewhat curved scales which show at the circumference PLANT DISEASE FUNGI 225 of the spore as a band about 2-4 jjl wide and on its top as polyg- onal areas 2-3 yu across; hyaline membrane more or less evident and often at one side in a short thread-like projection, 22-33 /* in length. Cross sections of stems bearing smutted heads reveal the my- celium in the chlorophyll parenchyma between the fibrous tissue. On rice. Urocystis Rabenhorst (p. 222) Sori usually in the leaves or stems, occasionally in other parts, producing dark-colored, usually dusty, spore-masses; spore- balls permanent, composed of an enveloping cor- tex of tinted sterile cells and usually one to sev- eral interior fertile cells; fertile cells generally dark-colored; germination often by a short pro- mycelium which produces terminally-grouped ^^of u^'^^X^ ^Af- sporidia; these give rise to similar secondary ter Thaxter. sporidia or to infection-threads. U. cepulae Frost. ^ Sori in leaves, forming isolated pustules or affecting them for the greater part of their length and breadth, sometimes occur- ring at their bases, in the bulbs. Upon rupture of the covering mem- brane a dusty, black- brown spore-mass ap- pears; spore-balls ovoid to spherical, 17-25 /j, in length; sterile cells tinted, Fro. 229.— U. cepute. Showing infection through the OVOid tO Sphcrical, Small, epidermal cell, from the outside of the cotyledon, the ,,0+ U^vt. i^/-»TviT^l/:»+/:kK7- r./^t7- hypha seeking the nucleus. After Anderson. Idbimi LOlIipieieiy Cov- ering the spores, usually 4-8 Ai in length; fertile cells reddish-brown, ovoid to spherical, usually 1, rarely 2 in a ball, chiefly 12-16 /x in length. On Allium. Infection usually occurs within 2 weeks after planting, and seed- lings are not susceptible after the 17th day. It probably is always through the cotyledon. The fungus once through the epidermis remains intercellular, spreading in all directions, sending occasional haustoria into the host cells. ^ Anderson, J. P. Development and pathogenesis of the onion smut fungus. Mass. Agr. Exp. Sta. Tech. Bui. 4, 1921. 226 PLANT DISEASE FUNGI Fig. 230. — U. cepulse. Stages of sporogenisis. A-P, development of a hooked cell and origin of the enveloping hyphae. Q, section through a young spore; R, surface view of a young spore; S, section through a mature spore. After Anderson. Fig. 231. — U. cepulse, germination of spores. After Anderson. PLANT DISEASE FUNGI 227 As the time for spore formation approaches the mycelium masses between the cells and branches profusely, forming twisted tangles which develop into the spore masses, the mycelial cells changing directly into spore cells by the intricate steps shown in Fig. 230. In germination the central spore produces a hemispherical vesicle (Fig. 231), the promycelium, from which branches arise. Sporidia if they occur are rare. Fig. 232. — Germination of spores of Urocystis tritici. After Noble. The fungus can live saprophytically in soil probably for years. U. tritici Koern.^ Sori in leaves, leaf-sheaths, stems and occasionally on glumes, forming elongated parallel streaks, at first covered by the raised, leaden-colored epidermis, which gradually decays in patches allowing the escape of the black, powdery spores. Spore-balls ^ Noble, R. J. Studies on the parasitism of Urocystis tritici Koern., the organism causing flag smut of wheat. Jour. Agr. Res. 27: 451, 1924. 228 PLANT DISEASE FUNGI globose, ellipsoid or oblong, bright golden brown, variable in size and shape, 16-40 m diam., or 24-40 x 24-32 ju averaging 32x24 fx; spores spherical or oval, 1-4 in a ball, occasionally 5, 9-12 /jl in diameter, or 12-16 ^t long; sterile peripheral cells generally com- pletely investing spores, pale yellow, ellipsoid to globose, and bulging, 9-12 /x long. On wheat causing flag smut. This species is mainly separated from U. occulta biologically. The spores are commonly two in a ball, although three and four are also found. The investing layer of sterile cells is generally complete. The spore is delicately punctulate on the surface, but this is more marked in U. occulta. U. occulta (Wallr.) Rab. Sori in leaves, especially in the sheaths, culms and inflores- cence, forming linear striae usually of great length and often merged into a continuous stratum of dusty, reddish-black, spore- balls; spore-balls oblong to subspherical, 16-32 n in length; sterile cells often incompletely covering the spores, hyaline or yellowish, subspherical to oblong, usually with distended and uniformly thickened walls; fertile cells red- dish-brown, oblong to subspherical, often flat- tened, smooth, 1 to 4 in a ball, 11-18 m in length. On rye wherever cultivated, though not com- Fig. 233.— Spore^balls HlOU in AmcHca. Thaxter"'*^' ^^^^^ The scat of spore formation is most often on the stems or sheaths, though all aerial parts of the plant are susceptible. In the vegetative parts the fungus is com- monly found in the tissue between the vascular bundles. U. violse (Sow.) F. de W. Sori on stems, rootstocks, petioles and leaves of violets form- ing prominent irregular swellings. U. agropyri (Preu.) Schr. Sori in various parts, commonly in leaves, forming striae, which may be distinct or cover the surface of the leaf; at first lead-colored and protected by the epidermis but soon rupturing and scatter- ing the reddish-brown spores; spore-balls oblong to subspherical, 16-32 n in length; sterile cells hyaline to yellowish, oblong to subspherical, usually completely covering the fertile cells, outer wall thin and by collapsing giving a ridged effect to the covering; spores 1 or 2, rarely 3 or 4 in a ball, reddish-brown, oblong to sub- spherical, often flattened, smooth, 11-18 fx in length. PLANT DISEASE FUNGI 229 On Agropyron and some other coarse grasses. Other species are on Gladiolus, Ornithogalum, pansy, primrose. Entyloma de Bary (p. 222) Sori usually foliar, generall}'^ forming discolored, but not distorted areas, permanently embedded in the tissues; spores single, pro- duced terminally or intercalary in the mycelium which does not entirely disappear through gelatinization, free, sometimes irregu- larly adhering through pressure, hyaline to yellowish or reddish- yellow, rarely dark-colored, germination by a short promycelium bearing a terminal group of sporidia which usually conjugate in pairs and produce secondary sporidia or infection-threads; sporidia often formed by germination of the spores in situ, the promycelium protruding through the stomata. Twenty American species are recorded. E. crastophilum Sacc. Sori in leaves, subcircular to linear, about 0.25-2 mm. in length, usually distinct though occasionally merged, black, long covered by the epidermis; spores dark-brown, tightly packed and adhering more or less, chiefly ovoid to spherical or angled through pressure, rather thick-walled, 8-14 ji in length. On Poa, Phleum, Agrostis and other grasses. E. irregular e Joh. also occurs on species of Poa; E. polysporum (Pk.) Farl. on sunflower. E. ellisii Hals. Sori in leaves, forming pale white spots, indefinitely limited, FiQ. 234. — E. ellisii, chlamydospores germinating within the leaf tissue, sporidia superficial. After Halsted. subconfluent; spores hyaline or slightly yellowish, clustered in the intercellular spaces beneath the stomata, spherical, thick-walled, (2-5 m) chiefly 16-20 /x but varying from 11-25' /x in diameter; 230 PLANT DISEASE FUNGI sporidia hypophylloiis, abundant, acicular, small, 10-14 n by less than 1 fx. On spinach. The chlamydospores germinate in situ beneath the stomata and bear the sporidia on tufts of promycelia which emerge through the stomata, presenting much the appearance of a Hyphomycete. Other species are on beet, Poa, Physalis, Solanum, poppy, and various water-lilies. Doassansia Cornu (p. 222) Sori in various parts of the host, usually in the leaves, rather permanently embedded in the tissues; spore-balls conspicuous, permanent, consisting of a distinct cortical layer and a central mass of fertile cells en- tirely filling the interior, or with the inner- most cells supplanted by parenchymatous cells or hyphal threads ; spores hyaline or yel- lowish, with smooth, usually thin, walls; ger- mination often in situ, by means of a short Fio. 235. — Doassansia. Part t u • u • • x j. • i section through a spore promycehum which gives rise to a terminal Kil^Si'^^flef Die'ieL ^^^up of elougatc sporidia, these often bear- ing secondary and even tertiary groups. D. gossypii Lagerh. is on cotton. Graphiola Poit. on various palms, is usually referred, doubt- fully, to the Ustilaginales. Protobasidii (p. 211) Uredinales ^' ^' ^' ^ The order is separated from the other orders of the Protobasidii by the basidia which arise from chlamydospores and have trans- verse septa. It is further characterized as follows. Small fungi, mostly microscopic, parasitic in the tissues of ferns and seed plants. Mycelium much branched, septate, and with haustoria. Spores mainly borne in sori below the surface of the host, or rarely single within the host. Sori naked or covered ^ Klebahn, H. Die Wirtwechselnden Rostpilze, Berlin, 1904. ^ Sydow. Monographia Uredinearum, Leipsig, 1904. ^Arthur, J. C. North American Flora, Urediniales, 1907. * Grove, W. B. The British Rust Fungi. Cambridge University Press, 1913. PLANT DISEASE FUNGI 231 at times, enclosed by peridia or paraphyses. Spores of five mor- phological sorts, not all present in every genus; (1) basidiospores, minute, thin-walled, without surface sculpturing, (2) pycniospores, small, smooth, of unknown function, (3) aeciospores, verrucosely sculptured, borne in chains, (4) urediniospores, echinulately or verrucosely sculptured, borne singly, or sometimes in chains, (5) teliospores, smooth or variously sculptured, borne singly or in chains. The order of some two thousand species, constituting the ''rust" fungi, many of them living on cultivated plants of high value, is of great economic significance. Its members are strict, obligate parasites which in no stage of the life except in the promycelial stage can develop other than on the living host. The complexi- ties of the life histories of the species, with their five distinct spore forms, inhabit- ing at different seasonal pe- riods two different host plants, renders the order both dif- ficult and exceedingly inter- esting. The life history of the most complete of these fungi may be stated as follows: I. -^cia (aecidia) and O. pycnia, often called spermo- gonia or pycnidia. The my- , . . • (, 1 • T Fig. 236. — iEcium and pycnium. After Tavel. cehum arismg irom a basidio- spore invades the host plant and vegetates until vigor sufficient to spore formation is attained, meantime often producing local spot- ting, hypertrophy, or other injury to the host. The myceUum then develops a stroma which produces spore beds, sori, and ruptures the epidermis. These sori are usually deeply sunken in the host and cup-shaped and take the common name ''cluster cups," Fig. 236, technically aecia, or aecidia. The sporophores arise from a hyphal plexus at the base of the cup and the spores are borne catenulate in acropetal succession. The whole structure is usually red or yellow. The outer layer of the cup usually consists of a o(\ 232 PLANT DISEASE FUNGI palisade of sterile sporophores bearing sterile cells and constitutes the peridium. The sedospores are usually nearly globular, or angular by compression, reddish and rough and sometimes bear germ pores. They are capable of germination at once and on germination give rise to germ tubes which may infect susceptible hosts, leading to a mycelium. This in turn again produces sori which in some species may be aecia, in others telia, but in most species, uredinia. Associated with the aecia, occasionally with other spore forms, but never borne alone, are minute pycnia with sporophores arising from their walls and bases. These bear unicellular pycniospores. Sterile hairs usually protrude from the ostioles. The whole struc- ture in gross appearance is much like the pycnidium of Phoma or Phyllosticta but it is reddish or orange in color. These pycnia were formerly spoken of as ''spermogonia" and the spores as "spermatia," due to the thought that they stood for degenerated male organs. Germination has now been observed and fertilization is known to occur elsewhere in the life-history and there is no longer reason to regard them as sexual organs. II. Uredinia (uredo-sori). The seciospores may infect the same species of plant that produced the seciospores (autoecious) or plants of an entirely different species (hetercecious) . The my- celium produced by the seciospore develops within the host, usually remains local, and causes spotting. When it has attained sufficient vigor and age, usually after about two weeks, it pro- duces a subepidermal hyphal plexus from which arises a bed of sporophores which bear unicellular, hyaline to brown, globose or elongated, usually sculptured spores, each with from 2 to 15 germ-pores variously placed. These are the urediniospores borne in uredinia (uredo-sori). They may germinate at once producing a germ tube which develops to a mycelium. These spores falling on susceptible tissues, by infection, usually stomatal, continue the production of uredinia and spread the dis- ease. The urediniospores are usually short-lived and function to spread summer infection. They continue to form throughout the growing season. In a few species there are what are known as amphispores or resting forms of urediniospores provided with thickened walls. They have colorless contents and pedicels more persistent than those of the usual urediniospore. III. Telia (teleuto-sori) . Toward the latter part of the growing PLANT DISEASE FUNGI 233 season another kind of spore appears, often in the same sorus with the urediniospore and from the same mycehum. It is of various forms in different genera, one or more-celled, varies in shape, thickness of wall, surface marking, color, etc., but is uni- form in the character of the germination which is very different from that of any of the other rust-spores. In teliospore germination, typically each cell of the teliospore sends forth one germ tube. These tubes soon cease growth and by septation become 4-celled. Each cell then sends out a short branch, sterigma, on which there develops one round or oval, 1-celled, thin-w^alled spore, the basidiospore, often in this group called the sporidium. Morphologically the promycelium is a basidium bearing its four sterigmata and four basidiospores. Relationship is thus shown on the one hand to the Ustilagin- ales, on the other hand to the Auricu- lariales, an assumption that is borne out by cytological evidence. Deviations from the typical mode of germination are found in several genera mentioned below (e. g., Coleosporium) . Basidiospores germinate immediately by germ tubes which on suitable hosts give rise again to pycnia and secia or in some species to other spore forms com- pleting the life cycle. The most complex life cycle is thus Fig. 237.— Germination of telio- seen to comprise pycniospores, «cio- St ""^ ^- ^"''^"^^'- ^^'"' spores, urediniospores, teliospores and basidiospores. For brevity the first four stages are commonly designated by the following symbols: 0. Pycnia or pycnial stage 1. JEicia, or secial stage 11. Uredinia or uredinial stage III. Telia or telial stage The spores in all cases, except those of the basidiospores and pycniospores arise directly from the mycelium. 234 PLANT DISEASE FUNGI Mesospore is a term appled to occasional unicellular forms of teliospores found in Puccinia and related genera which do not usually have unicellular teliospores. As has been said the pycniospores seem to be functionless though by some it is thought that they do function but that man has yet failed to find the conditions under which they readily germinate and cause infection. The secial stage appearing first, Fig. 238. — Amphispores, urediniospores and teliospores of Puccinia vexana. After Holway. and thus commonly in the spring, is often called the ''spring stage." It serves as an early stage to propagate and spread the fungus. The uredinia, often called the ''summer stage," constitute the phase usually of longest duration and of most injury. Its function is preeminently to multiply and spread the fungus. The telia, often called the "winter stage," usually, but not al- ways, constitute the resting, hibernating stage. In many instances the teliospores must rest over winter before they are capable of germination. Classification is based primarily on the teliospores. PLANT DISEASE FUNGI 235 While all five of the spore forms discussed above are typical of many species there are many other species which do not possess all of these forms or indeed which may possess only one spore form. Schroter for convenience groups the rusts, according to the spore forms that they show, under the following type names though it must be recognized that such grouping is purely arti- ficial and does not necessarily bring together closely related species. Eu-type 0, I, II, III present; Brachy-type O, II, III present; I omitted. Opsis-type O, I, III present; II omitted. Hemi-type II, III present; O, I omitted. Micro-type only III present; germination only after a resting period. Lepto-type only III present; germination without a resting period. As examples of the above we have the following: Eu-type, Puccinia asparagi, 0, 1, II, and III, all on Aspar- agus. Brachy-type, Puccinia suaveolens, O, II, and III, all on thistle. Opsis-type, Puccinia podophyUi, O, I, and III, all on May apple. Hemi-type, Puccinia antirrhini II, and III, both on snapdragon. Micro-type, Puccina ribis. III, on Ribes. Lepto-type, Puccinia malvacea- rum. III, on hollyhock. Hundreds of the hemi-types will doubtless be revealed by study to be heteroecious eu-types, while the micro and lepto-types each represent conglomerates of two different groups; one group of short-cycled rusts, possessing pycnia and telia, and another group in which telia only are known. Heteroecism.^ All of the examples just given are autcecious, i. e., all known spore forms are found on the same species of host plant. In many other rusts, however, heteroecism prevails, i, e., one stage of the fungus is found on one species of host and another stage upon another host; rarely three host plants are involved in the cycle. Aside from the rusts only one other fungus (Sclerotinia ledi) is known to show heteroecism. 1 Arthur, J. C. Cultures of Uredineffi. 1899-1917. Mycol. 13: 232, 1021. 236 PLANT DISEASE FUNGI Heteroccism has l)cen experimentally proved in some two hundred cases and may be assumed to exist in many cases not yet investigated. Examples of hetercecism are as follows: Eu-type, Puccinia graminis, triticina, sorghi, Uromyces pisi, Opsis-type, Gj^mnosporangium Juniperi-virginianse li a Stages 0, I. Stages II, IIL Berber is Wheat Thalictrum u Oxalis Corn Euphorbia Pea 1 Apple Red cedar (III) It frequently happens that part of the life cycle is passed upon a monocotyledonous plant, the remainder upon a dicotyledon. In such event it is more often the II and III stages that are on the mono- cotyledon while the O and I stages are on the dicotyledon; examples of this are afforded in the nu- merous rusts of grasses, sedges and rushes. In one group the pycnia and the secia are on pines (Perider- mium) , while the other stages are on dicotyledons. In the Gymnosporan- giums the pycnial and sBcial stages are on Rosacea ; the telial on Juniperus and its kin. While a few general rules can be worked out concerning host relations there are many exceptions and to know one stage of a hetercecious rust generally gives little or no clue to what its com- plementary host may be. The mycelium of the rusts is usually intercellular and local though in a few instances it is extensive and even perennial in Fig. 239. — Urediniospore of P. asparagi germinating on surface of plant, and separate spores. After Smith. PLANT DISEASE FUNGI 237 the host. It is abundantly branched, closely septate, gives off haustoria and usually bears numerous oil drops to which the dis- solved carotin imparts a yellow or orange color. Irritation by the mycelium often induces marked hypertrophy or even witches' brooms or other deformation of the host. Hy- pertrophy is most common with the secia but may result from the telia as well, as is conspicuously shown in the genus Gymno- sporangium. In some instances the whole habit of the host plant is altered by the presence of the mycelium so as to render it almost unrecognizable, e. g., the secium of Uromyces pisi on Euphorbia. The host cells are seldom killed by the mycelium, which ab- stracts its food supply from the carbohydrates and other nutrients of the cell sap without direct injury to the protoplasm, though ultimately there is serious effect upon both growth of the host and its seed production. Cytology. The mvcelial cells of the rusts are binucleate, a condition which begins just below the secium. The origin and significance of this condition is of much interest. Tt-> oU r\f +V>/-k T.no+o FiQ. 240. — Cross section, showing infection from spore of P. in an OI T;ne rusts asparagi. After Smith. so far investigated that have an secium or primary uredinium there is in the secio- mycelium or the primary uredinio-mycelium a fusion of uninu- cleated cells, gametes. This cellular fusion is not, however, fol- lowed by a nuclear fusion until after long delay; but the two nuclei remain in the fusion cell and when this cell divides both nuclei divide mitotically and simultaneously but still independ- ently of each other, conjugate division. This process continues through the secial sporophores, or uredinial sporophores, and in the production of the spores, with the result that the cells of all of these are binucleate. The conjugate division continues further through the uredinia and until teliospore formation occurs, the 238 PLANT DISEASE FUNGI whole inter v^ening series of cells being binucleate. Prior to the formation of the promycelium and in the teliospore the nuclei unite, reducing the cells again to an uninucleate condition. In rusts which have only teliospores the binucleate condition begins somewhere in the mycelium from which the teliospores arise. It is generally held that the cellular fusion is a sexual act with long delayed fusion of the sexual nuclei, and consequently that the uninucleate phase is the gametophyte; that the beginning of the binucleate condition marks the origin of the sporophyte. VQ^- Cm. t Fig. 241. — Showing con- jugate nuclei and degenerating cells in conidiospore chain of ^cidium. After Sap- pin-Trouffy. / ■■ v>.;A;i Fig. 242. — Gymnospo- rangium clavariseforme, mitosis of a nucleus in the promycelium. Af- ter Blackman. Fig. 243. — Conjugate nuclear division in Gymnosporangium cla- variseforme showing four chromatin masses. After Blackman. A word may here be given to the usually discredited mycoplasm theory of Eriksson. This affirms the existence in the cells of wheat grain of an intimate mixture of rust protoplasm and host proto- plasm. This mycoplasm may rest thus for months. Finally the host-cell nucleus becomes digested and the fungous plasm de- velops to a mycelium which proceeds to invade the surrounding tissues of the seedling as these develop on germination of the seed. Biologic specialization much as is found in the Erysiphales occurs also in the Uredinales. There are many species, each of which is found on a large number of hosts. Upon its numerous hosts the fungus may show no morphological variatioji, yet at- tempts to inoculate from one host to another may uniformly give negative results. PLANT DISEASE FUNGI 239 It further often occurs that one stage, e. g., the secia of a species may grow upon only one host while the uredinia or telia may grow upon many different species of hosts; and in such cases that seciospores which have arisen on host X, from infection with spores from host A, are capable of infecting host A and that host only; while seciospores which have arisen on host X, by infection with spores from host B, are capable of in- fecting host B and only this host; and so on for numerous forms. An excellent example of such biologic specialization is offered in the common pine Peridermium. ^Ecia may be produced upon the pine by sowing of Coleosporium telio- spores from Senecio, Campanula, Pulsatilla, etc., but the seciospores which develop on the pine are capable of infecting only those species of hosts from which the telio- spores were taken. Similarly Eriksson has determined that though rusts from many grains can infect the barberry, the seciospores there pro- duced are not capable of infecting plants ^'Lltri^cXolpucd^^^ of species other than those from which the fungus was derived, or at most they can infect but a very limited number of species. Further proof of the existence of biologic forms has recently been presented by Stakman. Infection Experiments. Since the method of studying the rusts by observing their life his- tories in the laboratory where they are under complete control of the observer has assumed such prominence of late years the technique deserves notice. The first step is to find asso- ciated in the field the secia and other stages of representation of fusion a rust in such Way as to suggest relationship of nuclei in the telio- ■, . . p I'n, i , -i spore. After Delacroix between two lorms hitherto unknown to be and Maublanc. cOnnectcd. Material of the rust is then collected and healthy host plants are also removed to the laboratory. If the teliospores are col- podophylli. man. After Christ- Fio. 245. — Diagrammatic 240 PLANT DISEASE FUNGI lected in the fall they are kept out of doors in cheese cloth bags till germination time in the spring. Whether collected in spring or fall the viability of the spores must be tested by showing in a hanging drop of water. If germination is plentiful then the infec- tion experiment is made. First the suspected alternate host is sprayed with water to give the spores proper conditions for ger- mination, then masses of spores are placed directly on the plant by a scalpel and a bell jar is placed over the plant to assure a humid atmosphere. In from five to eight days yellow spots should Fig. 246. — Urediniospores in Rubus showing nuclear conditions. After Biackman. indicate where the infection has taken place and in a short time pycnia and secia or other sori follow. In all infection work it is imperative to know that the plants used are not already infected in the field from another source. Form Genera. The telial stage is the one on which classification is often based. Thus an 2ecium, uredinium, cseoma, etc., that is known to possess a telial form is regarded as part of the species indicated by its teliospore, e. g., ^Ecidium berberidis being part of Puccinia graminis has no specific identity but is regarded as a stage of P. graminis. There are numerous uredinia, 2ecia and other non-telial forms of which the telial stage is not yet known. It becomes necessary for the present, for convenience of reference, to have names by PLANT DISEASE FUNGI 241 which to designate these forms. For this purpose the form-genera ^cidium, Caeoma, Peridermium, Roesteha and Uredo are recog- nized. We group these under the heading Uredinales Imperfecti. Darluca and TubercuHna, two imperfect fungi, are often found growing as parasites upon the rust fungi. Key to Families of Uredinales Teliospores in germination becoming 4-celled, compacted laterally into waxy layers; walls of the spores weakly gelatinous 1. Coleosporiaceae p. 241. Teliospores germinating by a promy- celium Teliospores compacted laterally into a crust or column (rarely solitary within the tissues); walls of the spores firm 2. Melamsporaceae, p. 245. Teliospores free or fascicled; walls of the spores firm or with an outer hygroscopic layer 3. Pucciniaceae, p. 254. Teliospores unknown 4. Uredinales Imperfecti, p. 278. Coleosporiaceae Teliospores united in a one or two4ayered, waxy cushion, ses- sile or borne on a broad sac-like stalk and then at the beginning 2-celled. Each original spore-cell divides to four super-imposed cells from each of which a simple sterigma emerges. This bears a large basidiospore. The most important character is the peculiar mode of basidio- spore production, the 4-celled promycelium being formed within the spore. Coleosporium Levielle Basidiospore ellipsoid, teliospores in a single layer in a flat crust. O. Pycnia flattish, linear, dehiscent by a slit, without ostiolar filaments. I(= Peridermium). ^Ecia erumpent, definite; peridium color- less with verrucose walls; spores globose to oblong, with colorless walls, the outer part formed of densely packed, deciduous tubercles. II. Uredinia erumpent, definite, without peridium; spores catenulate, globoid to oblong, pulverulent; wall colorless, closely verrucose, pores obscure. 242 PLANT DISEASE FUNGI III. Telia indehiscent except through weathering, waxy, some- what indefinite, usually roundish; spores sessile, 1-celled (by early division of the contents appearing 4-celled); wall smooth, colorless, thickened and gelatinous at apex. The genus is usually heteroecious. Arthur lists some twenty- four species for America. There are many biologic forms, morphologically indistinguish- able yet not inter-inoculable. The secial stage is found on leaves of conifefs, the telia on a large variety of hosts. C. ipomoeae (Schw.) Burr.S ^ O. Pycnia amphigenous, scattered or gregarious in rows, oliva- ceous-black, averaging 0.24 x 0.41 mm. I (=Peridermium ipomcese). ^cia flattened laterally, usually in a single row, averaging 0.4 x 1.6 mm.; peridial cells ovoid to elliptic or rhomboid in face view, mostly overlapping, averaging 21 x 41 ji, with walls 2-5 jjl thick, the inner closely and finely verrucose; seciospores ovoid to ellipsoid, 16-20 x 22-27 jj,, walls colorless and verrucose with somewhat deciduous tubercles 1-2 jn in diameter and 1-3 /x high. II. Uredinia hypophyllous, widely scattered or somewhat clustered, 0.25-1 mm. across, early naked, orange-yellow fading to white, ruptured epidermis usually inconspicuous; spores ellip- soid, 13-21 X 18-27 /JL, more or less angular and irregular; wall thin, 1-1.5 /JL, closely and noticeably verrucose. III. Telia hypophyllous, widely scattered, often confluent, pul- vinate, 0.5 mm. or less across, deep reddish-orange fading to pale- yellow; spores with wall swelling 20-40 /x above; contents orange- yellow fading to colorless, ol)long, or slightly clavate, 19-23 x 60-80 jjL, rounded or obtuse at both ends. Common on various Ipomoeas and their kin, among them morn- ing glory and sweet potato. J^]cia on Pinus echinata and various other pines. C. solidaginis (Schw.) Thiim. O. Pycnia amphigenous, scattered, numerous, originating be- tween mesophyll and cortical layer, noticeable, 0.3-0.5 mm. wide by 0.5-0.8 mm. long, dehiscent by a longitudinal slit, low- conoidal, 80-100 /x high. ^ Hedgcock, George G. & Hunt, N. Rex. New species of Peridermium. Mycol. 9: 239, 1917. - Hedgcock, George G. & Hunt, N. Rex. Notes on species of Coleosporium — II. Mycologia 14: 297, 1922. PLANT DISEASE FUNGI 243 I (=Pendermium acicolum). ^Ecia from a limited mycelium,, amphigenous, mimerous, scattered on discolored spots occup^dng part of a leaf, erumpent from longitudinal slits, tongue-shaped, 0.5-1 mm. long by 0.5-0.7 mm. high; peridium rupturing irregularly, mod- erately firm, white, cells overlapping, 35-45 IX long, not much narrower, walls transversely striate, inner coarsely verrucose, thick, 5-6 ^t, outer less rough and somewhat thinner; spores ellip- soid, 20-25 X 28-40 m; wall colorless, closely and coarsely verrucose with fig. 247.— stages o. and i. of Coieo- deciduous tubercles which are directed rpZs'rtfdT'XftS'Son.^ away from a smooth spot extending up one side, thick, 2-3 ix on the smooth spot, increasing to 5-6 /z on the opposite side, including the tubercles. II. Uredinia hypophyllous, rarely also epiphyllous, irregularly scattered, or at first somewhat gregarious and crowded, 0.3-0.5 mm. across, soon naked, yellow or orange-yellow, ruptured epi- dermis inconspicuous; spores ellipsoid or globoid, 17-22 x 20-30 /z; wall rather thin, 1-2 ix, closely and strongly verrucose; contents orange-yellow when fresh, fading to colorless. III. TeHa hypophyllous, scattered irregularly or sometimes crowded and confluent, slightly elevated, 0.3-0.5 mm. across, reddish-orange; spores with wall swelling 30-40 ^x thick above; contents orange-yellow fading to colorless, terete, 15-23 x 55-80 /x, rounded or obtuse at both ends; basidiospores globoid or elHptical, about 12x18 ix, orange-yellow. 0 and I on fourteen species of pine. II and III. Uredinia and telia on aster, Solidago. C. senecionis (Schum.) Fries O. Pycnia amphigenous, scattered, numerous, originating be- tween mesophyll and cortical layer, noticeable, 0.2-0.3 mm. wide, 0.5-1 mm. long, dehiscent by a longitudinal slit, 70-100 ix high. 1 ( = Peridermium oblongisporium) . ^Ecia from a limited mycelium, amphigenous, bullate, tongue-shaped, 1-2 mm. long, 0.7-1 mm. high, whitish; peridium rupturing irregularly, fragile, white, cells overlapping, outer and inner walls of same thickness, 3-4 IX, outer smooth, inner moderately verrucose; spores broadly ellipsoid, 17-24 x 28-36 yu, wall colorless, thick, 3-4 fx, densely verrucose with prominent elongate papillae. 244 PLANT DISEASE FUNGI II. Uredinia hypophyllous, thickly scattered, about 0.5 mm. across, early naked, bright orange-yellow fading to pale-yellow, ruptured epidermis evident; spores elliptical-globoid or obovate- globoid, 17-21 X 20-27 m; wall thin, 1-1.5 (i, evenly but not densely verrucose, with low papillae. III. Telia hypophyllous, scattered, often con- fluent, small, 0.3 mm. across, briUiant orange yellow fading to pale orange yellow; spores with wall swelling 15-25 /x thick above; contents orange yellow fading to pale yellow, clavate or clavate-oblong, 16-20 x 60-83 /x, rounded at both ends or narrowed below. I. ^cia on Pinus svlvestris. Fig. 248. — Coleosponum .. ". i . t n senecionis, showing ger- II and III. Urcdmia and telia on feenecio. S?ef pJowHgLr""- What may be this same fungus is reported also on cultivated Cineraria. The teliospores hiber- nate in their dark-red sori producing promycelia in the spring. The sporidia bring about spring infection of the pine leaves and young twigs, later resulting in pycnia and secia. C. pini Gall. 0. Pycnia unknown, probably wanting. III. Telia amphigenous, on yellow spots, usually near the tips of the leaves, long covered by the epidermis, 1-5 mm. long, or when confluent up to 10 mm. or more, reddish-orange fading to pale-yellow or dirty- white, ruptured epidermis inconspicuous; teliospores with walls swelling 30-50 m above, and soon disappear- ing upon exposure; contents orange-yellow fading to nearly colorless, clavate, slender, 13-20 x 60-100 m, acute or rounded above, much narrowed below, sides wavy or irregular. This is set spart by Arthur as the type of a distinct genus, Gallowaya, based on the absence of spore forms other than the teliospores. It causes serious leaf loss on Pinus virginiana. C. campanulae (Pers.) Lev. O. Pycnia amphigenous, scattered, numerous, originating be- tween mesophyll and cortical layer, noticeable, large, 0.2-0.4 mm. wide, 1-2 mm. long, dehiscent by a longitudinal slit, 90-110 /jl high. I ( = Peridermium rostrupi). ^Ecia from a hmited mycelium, amphigenous, scattered, 1-3 on discolored spots, bullate, tongue- shaped, large, 1-3 mm. long, 0.7-1.5 mm. high, yellow fading to PLANT DISEASE FUNGI 245 white; peridium rupturing irregularly, fragile, white, cells overlap- ping, outer and inner walls same thickness, about 4-6 n, outer smooth, inner moderately verrucose; spores broadly ellipsoid or globoid, 17-22 x 22-31 ii] wall colorless, thin, 2-3.5 ix, densely verrucose, with prominent, elongate papillae. II. Uredinia hypophyllous, scattered, often confluent, 0.5-1 mm. across, soon naked, orange-red fading to white, ruptured epidermis evident; spores elHpsoid, 18-23 x 20-30 m; wall thin, 1-1.5 m, densely verrucose with prominent, elongate papillae. III. Telia hypophyllous, scattered, often confluent, small, 0.2- 0.5 mm. across, slightly elevated, blood-red fading to pale brown- ish-yellow; spores with wall swelling 15-25 jj. thick above; contents orange-red fading to nearly colorless, cylindrical or clavate-oblong, 17-24 X 55-85 ^l, rounded or obtuse at each end. O and I on Pinus rigida. II and III on Campanula and kin. There are numerous other species of less importance. Melampsoraceae (p. 241) Telia forming a more or less definite crust or column; teliospores compacted laterally into layers or rarely solitary in the tissues, sessile; wall firm or rarely with a gelatinous layer. The family is of importance economically chiefly as the cause of flax rust and on pine, causing the bUster rust; its uredinial and telial stages also do slight injury on poplars and willows. Key to Genera of Melampsoraceae Telia indehiscent Sori all subcuticular; teliospores com- pacted in dense layers to form a crust; secia when present without a peridium; uredinia when present with delicate, cellular peridium with peripheral, free or imbricated para- physes or neither. Teliospores in a single layer; uredinia with spores and paraphyses inter- mixed 1. Melampsora, p. 246. Teliospores in more than one layer; uredinia wdth peridium or paraphy- ses or neither 2. Phakopsora, p. 248. 246 PLANT DISEASE FUNGI Pycnia subcuticular, other sori subepi- dermal, or the teha within the epider- mal cells or between the mesophyll cells; uredinia when present with a peridium Teliospores approximately in a single layer within or beneath the epider- mis; urediniospores globoid to ob- long Walls of the teliospores colored ; ure- diniospores echinulate through- out 3. Pucciniastrum, p. 248. Walls of the teliospores colorless; urediniospores echinulate 4. Melampsorella, p. 250. Telia erumpent, sori all subepidermal Telia velvety 5. Kuehneola, p. 251. Telia waxy; teliospores often firmly united sidewise and endwise, adher- ing and extruded in long columns; secia when present with inflated per- idium, dehiscence circumscissile; ure- dinia when present with peridium, spores borne singly on pedicels. Te- liospores 1-celled 6. Cronartium, p. 251. Melampsora Castaigne (p. 245) 0. Pycnia half spherical. 1. ^cia of cseoma-type, no peridium or paraphyses. II. Urediniospores solitary, membrane colorless. III. Teliospores 1-celled, rarely more, in flat irregularly limited crusts. Basidiospores spherical. The question of biologic specialization is especially complicated in this genus. The uredinal and telial stages occur in abundance on willows and poplars, the secial stage on a wide range of plants embracing gymnosperms, monocotyledons and dicotyledons. M. lini DC. 0. Pycnia amphigenous, numerous, scattered, inconspicuous, subepidermal, pale-yellow, flattened globoid or lens-shaped, 100- 175 IX in diameter, 65-95 n high; spores ellipsoid, 2-3 x 3-4 n. 1. .^cia chiefly hypophyllous, numerous, scattered, rounded, 0.2-0.4 mm. across, bright orange-yellow, conspicuous, formed be- tween epidermis and mesophyll, soon naked, ruptured epidermis evident; spores globoid, 19-27 x 21-28 n. ; wall colorless, thin, about PLANT DISEASE FUNGI 247 1 ix, finely and evenly verrucose, with distinct papillae, pores not evident. II. Uredinia amphigenous and caulicolous, scattered or some- what gregarious, often crowded, round or on stems elongate, 0.3-0.5 mm. across, soon naked, reddish-yellow fading to nearly white, pulverulent, ruptured epidermis noticeable; spores broadly elliptical or obovate, 13-18 x 15-25 /x, wall colorless, rather thin, 2 fjL, evenly and finely verrucose, with low papillae, pores equatorial, obscure; paraphyses intermixed with the spores, capitate, large, 5-22 X 40-65 /a, smooth, wall thick. III. Telia amphigenous and caulicolous, scattered, often con- fluent, round or elongate, 0.2-0.5 mm. across, slightly elevated, reddish-brown becoming blackish; spores subepidermal, appressed into a single layer, prismatic, 1-celled, 10-20 x 42-50 fx; wall brown, smooth, thin, about 1 fx, not thickened above. Autoecious on flax. Sometimes injurious. M. medusae Thiim. 0. Pj^cnia chiefly epiphyllous, scattered or somewhat gregari- ous, minute, punctiform, pale-yellow, inconspicuous, subcuticular, hemispherical, 40-80 u in diameter, half as high. 1. iEcia chiefly hypophyllous, scattered or somewhat gregari- ous, small, 0.1-0.3 mm. broad, round or oblong, pale-yellow fading to white, inconspicuous, formed between epidermis and mesophyll, soon naked, pulverulent, ruptured epidermis notice- able; seciospores globoid, 17-22 x 17-24 /ul; wall colorless, thick, 2.5-3 fx, finely verrucose, with minute crowded papillae, pores in- distinct. II. Uredinia amphigenous, or only hypophyllous, scattered, roundish, small, 0.2-0.4 mm. across, early naked, somewhat pul- verulent, orange-yellow, fading to pale brownish-yellow, ruptured epidermis usually inconspicuous; urediniospores ellipsoid or obovate-ellipsoid, 15-18 x 22-30 /x, usually flattened laterally; wall colorless, 2.5-3 /j, or up to 10 jjl on the flattened sides, sparsely and evenly verrucose with fine papillae, except on the flattened sides which are smooth ; paraphyses numerous, intermixed with the spores, capitate, smooth, 40-65 fx long, head 14-25 ix broad, wall thick, 3-6 fx, peripheral paraphyses thinner-walled and more cla- vate. III. Telia amphigenous or only hypophyllous, scattered or somewhat confluent, irregularly roundish, small, 0.2-0.4 mm. across, slightly elevated, light reddish-brown, becoming deep 248 PLANT DISEASE FUNGI chocolate-brown, subepidermal; teliospores prismatic, 12-15 x 30-45 ii; wall smooth, cinnamon-brown, uniformly thin, 1 ix. O and I on larch, II and III on poplar. Common on all species of Populus and often doing serious damage by its early defoliation of the trees. Eight other species are recorded with the stage II, III on Salix, 8 on Populus; three of these have the stage I on Larix; others are on Allium, Ribes, Tsuga, etc. M. saliciscaprae (Pers.) Wint. is injurious on willow. Phakopsora Diet el (p. 245) Cycle of development imperfectly known; only uredinia and telia recognized, both subepidermal. Uredinia erumpent, definite, roundish, pulverulent, with delicate cellular peridium, with pe- ripheral free or imbricated paraphyses or neither. Urediniospores sessile, apparently produced in chains with one spore maturing at a time and falling away before the next one enlarges, obovate-glo- boid or ellipsoid; wall pale-yellow, echinulate or rarely verrucose, pores obscure. Telia indehiscent, forming lenticular masses, two or more cells thick at center. Teliospores 1-celled; walls smooth. P. vitis (Thiim.) Syd. II. Uredinia hypophyllous, scattered thickly over wide areas, round, minute, 0.1 mm. or less across, soon naked, arising between epidermis and mesophyll, surrounded by numerous incurved pa- raphyses, pulverulent, pale-yellow, fading to dirty white, ruptured epidermis inconspicuous; urediniospores broadly ellipsoid or obo- vate, 13-17 x 18-27 fx; wall nearly colorless, thin, 1 /z, minutely and rather closely echinulate, pores obscure; paraphyses hyphoid, curved and irregular, 6-10 /x thick, 30-60 /z long, wall uniformly thin, 1 IX, yellowish. III. Telia hypophyllous, scattered thickly over large areas, roundish, minute, 0.1-0.2 mm. across, indehiscent, 3-4 cells thick; teliospores ovoid, 12-15 x 20-30 /x, wall smooth, nearly colorless, thin, 1 /x or less. On grape leaves in Southern United States and West Indies. Also in South America and Japan. Pucciniastrum Otth. (p. 246) Hetercecious. The cycle of development includes pycnia, aecia uredinia and telia, with distinct alternating phases. PLANT DISEASE FUNGI 249 0. Pycnia subcuticular, low-conoidal, without ostiolar fila- ments. 1. ^cia erumpent, cylindrical. Peridium delicate, verrucose on inner surface. Spores ellipsoid, verrucose except one side which is thinner and smooth. II. Uredinia barely protruding through the epidermis, dehis- cent by a central pore. Peridium hemispherical, delicate, cells longer at orifice. Spores borne singly on pedicels, obovate to ellipsoid; wall colorless, echinulate, pores in- distinct. III. Telia indehiscent, forming more or less evident layers in the epidermal cells or immediately be- neath the epidermis. Spores oblong or prismatic, 2 to 4-celled by verti- cal partitions in two planes; wall smooth, colored. P. hydrangeae (B. & C.) Arth. O and I. Unknown. II. Uredinia hypophyllous, scat- tered, round, small, 0.1-0.2 mm. across, dark-yellow fading to pale- yellow, ruptured epidermis incon- spicuous, dehiscent by a central pore; peridium hemispherical, deli- cate, cells small, cuboid, walls uni- formly thin, 1-1.5 /z, ostiolar cells slightly or not elongate, 10-16 /jl, barely pointed, walls thin, smooth; spores broadly elliptical or obovate, 12-18 x 16-24 fx; wall nearly colorless, thin, 1-1.5 fx, sparsely and strongly echinulate. III. Telia amphigenous or chiefly epiphyllous, effused or confluent into small angular groups, 0.3-0.8 mm. across, not raised, reddish-brown ; spores forming a single layer within the ep- idermal cells or sometimes between the epidermis and mesophyll, globoid, 22-28 x 24-28 fx, wall dark cinnamon-brown, uniformly thin, 1.5-2 ju. It is found in the uredinial and telial stages on Hydrangea on which it may be quite serious. Fio. 249. — Pucciniastrum showing ger- minating teliospores. After Hartig. 250 PLANT DISEASE FUNGI Melampsorella Schroter (p. 246) 0. Pycnia hemispherical, without ostiolar filaments. 1. JEcia, erumpent, definite, oblong, bullate; peridium colorless, with thin-walled cells; seciospores ellipsoid; wall colorless, thin, verrucose, without smooth spot. II. Uredinia barely protruding through the epidermis, dehiscent by a central pore; peridium hemispherical, delicate, cells slightly or not enlarged at orifice ; urediniospores borne singly on pedicels, obovate to ellipsoid; wall slightly colored, echinulate, pores ob- scure. III. Telia effused, indehiscent; teliospores globoid to ellipsoid, 1-celled; wall smooth, colorless, thin. M. elatina (A. & S.) Arth. 0. Pycnia epiphyllous, few, scattered, punctiform, inconspicu- ous, subcuticular, not extending far into walls of epidermis, de- pressed-hemispherical, small, 100-130 ^ broad, 40-50 m high. 1. ^cia from a perennial mycelium, dwarfing the young shoots and forming witches' brooms, hypophyllous, forming two ir- regular lines, deep-seated, wholly dropping out of the substratum at maturity, roundish or irregularly oblong, large, 0.5-1 mm. across, bladdery, soon open by falling away of the upper part; peridium colorless, dehiscence irregular, cells with thin inner and outer walls; seciospores broadly ellipsoid or nearly globoid, 14- 18 X 16-28 At; wall colorless, thin, 1-1.5 fi, closely and rather finely verrucose. II. Uredinia amphigenous, scattered or somewhat grouped, small, round, 0.1-0.4 mm. across, orange-red when fresh, pale yellow when dry; peridium hemispherical, dehiscent by a small central orifice, cells elongate at sides, polygonal above, inner and outer walls same thickness; urediniospores ellipsoid or obovoid, 12-18 X 16-30 m; walls pale yellow, rather thin, 1-1.5 n; sparsely echinulate with short conical points. III. Telia hypophyllous, on whitish or pale reddish spots; tel- iospores within the epidermal cells, 1-celled, short-cylindrical or polygonal, 13-20 /x broad; wall colorless, smooth, thin. I (=Peridermium elatinum) on fir causing swelling, cankers and witches' brooms. II and III on various members of the pink family. All stages possess perennating mycelium. The secial stage is of most economic significance, producing witches' brooms of various PLANT DISEASE FUNGI 251 sizes. The secia are formed only on the deformed needles of the witches' brooms. Kuehneola Magnus (p. 246) Mcisi wanting; uredinia pulvinate, telia similar to Phragmidium but with smooth spores with the germ pores apical. K. uredinis (Lk.) Arth. II (=Uredo muelleri). Uredinia lemon-yellow, minute dots; spores globose to elliptic, about 26 fi, hyaline, slightly verrucose. III. Telia solitary, pale, 250-500 ji broad; spores 5 to 6 to 12-celled, epispore hyaline, cells 17-47 x 15-26 /x; basidiospores 8.5-9.5 fjL. The telia are pale yellowish-white, thus readily distinguishing them from other Rubus rusts. The uredinia are common and sometimes injurious on Rubus. The sori are small and scattered. Cronartium Fries (p. 246) 0. Pycnia deep-seated, broad and flat. I (=Peridermium). ^Ecia erumpent, inflated; peridium mem- branous, rupturing at the sides rather than above, 2-4 cells thick, outer surface smooth, inner verrucose. Spores ellipsoid; wall colorless, coarsely verrucose with deciduous tubercles, except a smooth spot on one side. II. Uredinia somewhat erumpent; peridium moderately firm, rupturing above, upper part evanescent; peridial cells isodia- metric; spores borne singly on pedicels, globoid to ellipsoid; wall nearly or quite colorless, echinulate, pores obscure. III. Telia erumpent, at first arising from the uredinia, the catenulate spores adhering to form a much extended, cylindrical or filiform column, horny when dry; spores oblong to fusiform, 1-celled; wall slightly colored, thin, smooth. All known secial stages are Peridermiums on stems of conifers. C. ribicola F. de Wal. 0. Pycnia caulicolous, scattered, honey-yellow, forming minute, bladdery sweUings. Spores hyaline, ovoid to elliptical, 1.9-4.7 /x. I (=Peridermium strobi). ^cia caulicolous, causing fusiform swellings of the stem, rounded to elongate; peridium inflated, rup- turing at sides, thick, membranous; spores ellipsoid to ovoid, 252 PLANT DISEASE FUNGI 18-20 X 22-23 ix, wall colorless, coarsely verrucose except on elongate smooth spot, 2-2.5 ix thick, on smooth spot 3-3.5 /z thick. II. Uredinia hypophyllous, thickly scattered in groups, round, pustular, 0.1-0.3 mm., at first bright yellow; peridia delicate; Fig. 250. — Cronartium. A, uredinium; B, telium. After Tubeuf. spores ellipsoid to obovate, 14-22 x 19-35 ix, wall colorless, 2-3 ^u thick, sparsely and sharply echinulate. III. Telial columns hypophyllous, cylindrical, 125-150 ti thick, up to 2 mm. long, curved, bright orange-yellow becoming brown- ish; spores oblong or cylindrical, 8-12 x 30-60 /x; wall nearly colorless, smooth, rather thick, 2-3 /x. Hetercecious O, I, on white pine, Pinus cembra and several other 5-leaved species; II and III on currant and gooseberry and several other species of Ribes. The telial stage was first noted in Geneva, N. Y., in 1906, though the rust has been known in Europe since 1854. Its effects are most serious in its secial stage, though the telial stage is very abundant and conspicuous. The generic con- nections of the forms was proved by Klebahn in 1888 by in- oculations. The mycelium is doubtfully perennial in Ribes and certainly is perennial in the bark of the pine. C. comptoniae Arth. I (=Peridermium pyriforme) on Pinus trunks. Ill on Comp- tonia. The Peridermium is perennial in the trunks of the pine where it does considerable injury. PLANT DISEASE FUNGI 253 C. filamentosum (Pk.) Hedg. (=Peridermium filamentosum Pk.) is the most destructive Peridermium on pine in the West. The alternate stage is on Castilleja. C. cerebrum (Pk.) H. & L. Heteroecious; I (= Peridermium cerebrum) on pine, III on oak. Globoid swellings 5-25 cm. across are formed on pine trees. Fig. 251. — Cronartium comptoniae (Peridermium) on Pinus. After Clinton. C. occidentale Hedgcock, Bethel & Hunt.^ 0 and I on Pinus edulis and P. monophylla. II and III on Ribes sps. and Grossularia sps. This Rocky Mountain rust in its uredinial and telial stages is quite similar to C. ribicola with which it has been confused in the past. It is only known to attack one- and two-needled pines and does not affect the five-needled pines. C. pyriforme (Pk.) Hedgcock and Long.^ 1 on Pinus spp. II and III on Comandra spp. This rust is widely distributed over the United States attacking in its secial form two- and three-needled pines. It produces cankers ^ Hedgcock, George G., Bethel, Ellsworth, and Hunt, N. Rex. Pifion blister-rust. Jour. Agr. Res. 14: 411, 1918. ^ Hedgcock, G. G. and Long, W. H. A disease of pines caused by Cronartium pyri- forme. U. S. Dept. Agr. Bur. PI. Ind. Bui. 247, 1915. 254 PLANT DISEASE FUNGI and slight fusiform swellings which usually encircle the trunks, in young trees, killing the cambium and thus leading to the destruc- tion of the tree. Pucciniaceae (p. 241) Teliospores stalked, stalk sometimes short or evanescent, 1-celled or with several cells in a row or several united to form a parasol-like head on a compound stalk; separate or gelatinous- embedded; basidiospores formed from promycelia. iEcia with or without peridia; urediniospores solitary. This is the largest and most important family of the order, in- festing numerous valuable agricultural plants and causing enor- mous loss. The species are manifold and the complexities, owing to polymorphism, heteroecism and biologic specialization, are very great. Key to Genera of Pucciniaceae Teliospores free, 2-8 at apex of a com- mon stalk; all spore forms present 1. Tranzschelia, p. 255. Teliospores not borne on a common pedicel Teliospore wall without gelatinous layer Pycnia subcuticular, other sori subepidermal ; secia when present without peridium ; uredinia when present with- out peridium, but usually with encircling paraphyses Teliospores mostly tuberculate, the pores more than one and lateral, with more than three cells lineally arranged 2. Phragmidium, p. 256. Teliospores 2-celled, mostly smooth, the pores one in a cell and apical 3. Gymnoconia, p. 257. Sori all subepidermal; secia when present with a peridium; ure- dinia when present with no peridium or rarely with en- circling paraphyses Teliospores embedded in a more or less gelatinous matrix ... 4. Gymnosporangium, p. 258. PLANT DISEASE FUNGI 255 Teliospores not embedded iii a gelatinous matrix, dark col- ored Teliospores 1-celled 5. Uromyces, p. 265. Teliospores 2-celled 6- Puccinia, p. 268. Tranzschelia Arthur (p. 254) Cycle of development includes pycnia, secia, uredinia and telia, with alternating phases; autoecious or hetercecious; pycnia sub- cuticular, other sori subepidermal. O. I. Pycnia depressed-conical or hemispherical; hymenium flat; secia erumpent, cylindrical; peridium dehiscent at apex, becoming recurved. ^Eciospores globoid; wall colored, finely verrucose. v^;\ 'ISBBK^ r^ ^s v^v •*' t' %. !S«rt-» i \ ''"\ / Fig. 252 — T. punctata, urediniospores. After Holway. II. Uredinia erumpent, definite, without peridium; uredinio- spores borne singly on pedicels, with paraphyses intermixed, obovoid, somewhat narrowed at both ends; wall colored, usually paler below, echinulate; pores equatorial. III. Telia erumpent, definite, pulverulent, without peridium; teliospores forming heads or balls by being attached by short, 256 PLANT DISEASE FUNGI fragile pedicels to a common stalk, which is short and inconspicu- ous, 2-celled by transverse septum, cells rounded and easily falling apart, wall colored, verrucose. T. punctata (Pers.) Arth. I (=iEcidium punctatum). ^cia uniformly scattered over the leaf, hypophyllous, flat, semi-immersed, with torn yellowish edges; spores subglobose, pale yellowish-brown, 15-24 /x in di- ameter; pycnia scattered, blackish, punctiform. II. Uredinia light-brown, small, round, crowded, pulverulent, often confluent; spores ovate or subpyriform, apex darker, thick- ened, bluntly conical, closely echinulate, brown, 20-35 x 12-16 ^, mixed with numerous capitate brownish paraphyses. III. TeHa pulverulent, dark-brown, almost black; spores con- sisting of two spherical cells, flattened at their point of union, the lower cell often being smaller and paler; epispore uniformly thick, chestnut-brown, thickly studded with short stout spines. Spores 30-45 x 17-25 /a; pedicels short, colorless. Heteroecious : 0 and I on Hepatica, Thalictrum and Anemone. II and III on Prunus sps., peach, almond, plum, cherr}^, apricot. The secial stage is perennial. Urediniospores have also been shown to remain viable over winter. The peculiar character of the urediniospores has sometimes led this fungus to be mistaken for a Uromyces. Phragmidium Link (p. 254) 0. Pycnia present. 1. ^ciospores in basipetal chains. The first two spore forms m Fig. 253. — Uredinio- and teliospores of: 1. P. americanum; 2. P. rosse-setigerai; 3. P. rosae- californicse; 4. P. rosae-arkansanse; 5. P. montivagum; 6. P. disciflorurn. After Arthur. PLANT DISEASE FUNGI 257 are in pulverulent sori, surrounded by clavate or capitate, hyaline paraphyses. II. Urediniospores single. III. Teliospores separate, pedicellate, consisting of from three to ten superimposed cells, the uppermost of which has a single apical germ pore, the others about four each, placed laterally. The secial stage is a Caeoma, but with a border of incurved pa- raphyses. The unicellular urediniospores are similarly surrounded, and bear numerous germ pores. The genus is limited to rosaceous hosts and its species are autoecious. Eight American forms are recognized by Arthur on roses. Gymnoconia Lagerheim (p. 254) O. Pycnia conic. I (= Caeoma) peridia and paraphyses none. III. Spores as in Puccinia. This genus bears a superficial resemblance to Puccinia but is easily distinguished by its naked aecial sori. G. interstitialis (Schl.) Lag.^ O. Pycnia glandular, numerous, mostly epiphyllous. I (= Caeoma nitens) hypophyllous, sori irregular, confluent; spores orange-red, globose to elliptic, epispore thin, 18-35 x 12-24 jjl. III. Telia hypophyllous, few, sparse, cinnamon-brown; spores more or less angular, 36-45 x 22-27 ix, pedicel short or wanting. Autoecious on raspberries, wild and cultivated. The pycnial stage appears first in spring giving to the leaves and stems a glandular appearance. About two or three weeks later the aecial stage is visible on the lower surface of the leaves; the epidermis soon ruptures and the orange beds of spores show. The pycnia are then fully developed. The affected plants are much stunted and unproductive, but are not killed. The fungous mycelium is intercellular, growing rapidly into formative tissues and perennating in the woody shoots. The knob-like haustoria penetrate the cells and often lie against the nuclei. The mycelium is especially abundant in the pith near the bundles. ^ Kunkel, L. P. The production of a promycelium by the aecidiospores of Caeoma nitens. Bui. Torr. Bot. CI. 40: 361; also, Nuclear behavior in the promycelia of Caeoma nitens Burrill & Puccinia peckiana Hawes, Amer. Jour. Bot. 1: 37, 1914; same author. Further studies of the orange rusts of Rubus in the United States. Bui Torr. Bot. CI. 43: 559, 1916; same author, Further data on the orange rusts of Rubus. Jour. Agr. Res. 19: 501, 1920. 258 PLANT DISEASE FUNGI The seciospores may germinate at once and infect susceptible hosts. The teliospore which is less conspicuous and therefore rarely seen is of the Puccinia type. The telia appear in July and August, usually hypophyllous, and the sori are very small and inconspicuous. A second form of this rust, almost indistinguishable from the first, occurs on wild and cultivated blackberries; the chief differ- FiQ. 254. — G. interstitialis, cseoma sorus. After Newcomb. ence rests in the manner of germination of the spores, which in the second form produce promycelia, hence functioning as telio- spores, while those of the other form produce germ tubes. Owing to this fundamental difference in germination, constituting one form as a short cycle rust, together with very slight difference in color and size of the spores, this second form is regarded by some as a distinct species belonging in a separate genus, Kunkelia. Gymno sporangium Hedwig ^' ^ (p. 254) Cycle of development including pycnia, secia and telia, with distinct alternating phases; heteroecious and autoecious. Pycnia and other sori subepidermal. 1 Kern, F. D. A biological and taxonomie study of the genus Gymnosporangium. Bui. N. Y. Bot. Gard. 7: 391, 1911. 2Sydow. Monog. Ured. 1915. * PLANT DISEASE FUNGI 259 O. Pycnia deep-seated, usually globoid, generally prominent and conspicuous, at first honey yellow, usually becoming blackish, globose or flattened-globose, with ostiolar filaments. I (=RoesteHa) erumpent, at first cylindric. Peridium dingy white, usually elongated into a tubular form, membranous, tending to rupture by longitudinal sHts along the sides; peridial cells im- bricate and often articulated, occasionally hygroscopic, outer walls smooth, rather thin, inner walls smooth, verruculose, verrucose, rugose, or spinulose. iEciospores in basipetal chains with alter- nate barren cells, inclosed in a peridium, globoid to broadly ellip- soid; wall colored, verrucose, usually with numerous, scattered, evident germ pores. III. Telia erumpent, naked, usually definite, variously shaped, gelatinous and elastic at maturity, expanding considerably when Fig. 255. — Gymnosporangium, spore masses just emerging. After Heald. moistened. Teliospores chiefly 2-celled, in some species 3, 4, or 5-celled, by transverse septa; walls colored, of various thickness, smooth; pores usually two in each cell, sometimes, 1, 3, or 4, vari- ously arranged; pedicels hyaline, elastic, usually of considerable length, cylindric, rarely carotiform, walls thick, the outer portion swelling and becoming gelatinous to form a jelly-like matrix in which the spores appear embedded. All of the species agree in possessing the same spore forms, pycnia, secia, and telia which appear in the same sequence in the 260 PLANT DISEASE FUNGI different species; also in the fact, with two exceptions, that the secia grow on pomaceous plants, and the telia on Juniperus (with few exceptions). The 2eciospores are borne in secia which rest in orange or yellow spots often strongly thickened. Pycnia abound. The secium with its thick perid- ium is erumpent and projects to some dis- tance above the host surface, this charac- ter giving rise to the separate form-genus, Roestelia. The pe- ridial margin which may be lacerate or fimbriate is used in specific characteriza- tion. The spores are borne and function as in ordinary secia. They bear several germ pores. iEciospores germi- nate at once and if they fall upon suit- able coniferous hosts bring about infec- tion. The mycelium penetrating the leaf or branch often in- duces large hyper- trophy. In spring in moist weather the telio- Fi 256. — Gymnosporangium teliospores. o, G. clavarise SporCS are lOUnCl m forme; h, G. globosum; c, G. macropus; d, G. nidua-avis „v~»/^»»/-k tv»occ/:icj r>r\m e, G. nelsoni; /, G. clavipes. After King. Spore maSbeS COIIl- posed of the spores, which are usually orange or yellow, and of their long gelatinous pedicels. Each cell bears one or more germ pores through one of which the tube emerges. PLANT DISEASE FUNGI 261 The teliospores germinate immediately in situ by typical 4- celled promycelia and four basidiospores are produced on each promycelium. The basidiospores are capable of infecting only the appropriate alternate host and that when the parts are still young and tender. The various species usually make good subjects with which to study infection. The teliospore masses placed in water soon be- come covered with basidiospores. Suspensions of these in water applied to susceptible hosts usually give positive results readily. G. juniperi-virginianae Schw. (=G. macropus) Link. 0. Pycnia epiphyllous. 1. iEcia (=Roesteha pyrata) chiefly hypophyllous, usually in annular groups, on thickened discolored spots, at first cylindric, 0.1-0.4 mm. in diameter; peridium splitting extremely early, becoming fimbriate to the base, strongly revolute; peridial cells usually seen only in side view, long and narrow, 10-16 x 65-100 fi, becoming much curved when wet, inner and side walls rather sparsely rugose with ridges extending half way across the side walls; seciospores globoid or broadly ellipsoid, 16-24 x 21-31 /x, wall light chestnut-brown, 2-3 /jl thick, finely verrucose. III. Telia appearing on globoid or reniform galls 5-30 mm. or more in diameter, evenly disposed, cylindric or cylindric-acumi- nate, 1.5-3 mm. in diameter by 10-20 mm. long, golden-brown; teliospores 2-celled, rhombic-oval or narrowly ellipsoid, 15-21 x 42-65 fi; slightly or not constricted at the septum; wall pale cinna- mon-brown, thin, about 1 ju; pedicel cylindric, 3-5 /z in diameter; pores two in each cell near the septum. I. ^cia on apple both wild and cultivated. III. Telia on Juniperus virginiana and J. barbadensis. Destructive, particularly in East and South. Sporidia are matured in twelve to twenty-four hours after the spore-masses expand by moisture, and as soon as the sori begin to dry they are carried away by wind and on suitable hosts infect, through the cell walls, by appresoria. Two or three crops of spori- dia may arise in one season but the first crop is largest. Each crop may result in a corresponding crop of secia. The stage on apple fruits shows as pale yellow spots of pinhead size about seven to ten days after infection. The spots finally become orange colored and in a few weeks the pycnia appear as black specks. On leaves hypophyllous cushions 0 . 5-1 cm. in diameter form on the spots and bear the secia, the mature tubes of which are split and 262 PLANT DISEASE FUNGI recurved giving a stellate appearance. iEciospores pass back to the cedar in summer and cause infection. The mycelium here remains practically dormant imtil the following spring when the telial galls first become visible. These galls grow throughout the summer, mature in the fall, and give rise to the teliospores during the next spring. The mycelium is thus seen to be biennial. G. clavariaeforme (Jacq.) DC. I. JEcisi hypophyllous, fructicolous or caulicolous, usually crowded in small groups 2-3 mm. across on the leaf blades, some- times in larger groups on the veins, petioles and twigs, often densely aggregated on the fruits and occupying part or all of the surface, cylindric, 0.7-1.5 mm. high by 0.3-0.5 mm. in diameter; perid- ium soon becoming lacerate, usually to base, erect or spread- ing; peridial cells long and narrow, often becoming curved when wet, linear in face view, 18-30 x 80-130 /z, linear or linear-oblong in side view, 15-25 fx thick, outer wall 1-2 /x thick, smooth, inner wall and side walls 5-7 fi thick, rather coarsely verrucose with roundish or irregular papillae of varying sizes; seciospores globoid, 21-27 X 25-30 ju, wall light cinnamon-brown, 2.5-3.5 n thick, moderately verrucose. III. Telia caulicolous, appearing on long, fusiform swellings of various sized branches, numerous, scattered or sometimes aggre- gated, cylindric, or slightly compressed, 5-10 mm. long by 0.8-1.5 mm. in diameter, acutish, or sometimes forked at the apex, brownish-yellow; teliospores 2-celled, lanceolate, 13-20 x 40-80 fx, occasionally longer, rounded or narrowed above, usually narrowed below, very slightly or not at all constricted at the septum; wall golden-yellow, thin, about 1 jjl; pores 2 in each cell, near the sep.tum. I. iEcia on Crataegus spp., Amelanchier, Aronia, Cotoneaster, Cydonia, and Pyrus. III. Telia on Juniperus communis, J. oxycedrus, and J. sibirica. Spindle-shaped swellings -occur on Juniper branches. Cylindric spore-masses ooze through rifts in the bark. ^Eciospores shed in June germinate at once on Juniper twigs and result in the following year in swellings which often later cause death. In spring the spore-masses emerge and the teliospores germinate i?i situ. Upon the rosaceous hosts spots appear eight to fourteen days after infection. G. globosum Farl. O. and I. JEcisL chiefly hypophyllous and crowded irregularly or rarely in approximately annular groups 2-7 nun. across, cylin- PLANT DISEASE FUNGI 263 dric, 1.5-3 mm. high by 0.1-0.2 mm. in diameter; peridium soon splitting in the upper part, becoming reticulate half way to base; peridial cells seen in both face and side views, broadly lanceolate in face view, 15-23 x 60-90 lu, linear rhomboid in side view, 13-19 /x thick, outer wall about 1.5 /x thick, smooth, inner and side walls 3-5 fjL thick, rather densely rugose with ridge-like papillae of varying length; seciospores globoid or broadly ellipsoid, 15-19 x 18-25 fjL, wall light chestnut-brown, 1.5-2 /x thick, finely verru- cose. III. Telia caulicolous, appearing on irregular globoid, gall-like excrescences 3-25 mm. in diameter, unevenly disposed, often separated by the scars of the sori of previous seasons, tongue or wedge-shaped, 1.5-3 mm. broad by 2-5 mm. long at the base and 6-12 mm. high, chestnut-brown.; teliospores 2-celled, ellipsoid, 16-21 X 37-18 /z, somewhat narrowed above and below, slightly constricted at the septum; Avail pale cinnamon-brown, 1-2 /x thick; pores 2 in each cell, near the septum. I. ^cia on apple, pear, Crataegus, mountain ash. III. Telia on Juniperus virginiana and J. barbadensis. Common and widely distributed in eastern America. The telial galls are from 0.5 to 2.5 cm. in diameter, very ir- regular. In late spring dark-brown spore-masses, later yellow- orange, 0.5 to 2.5 cm. long appear. The Roestelia spots are 0.5-1.0 cm. across. Pycnia blackish above. The secia are on thickened hypophyllous spots, long, slender, soon splitting and becoming fimbriate. Mesospores occur occasionally. The seciospores germinate on the cedar. The mycelium stimulates the hosts to extra formation of parenchy- matous tissue. G. juniperinum (L.) Mart. I. iEcia (= Roestelia penicillata [Pers.] Fries.) hypophyllous, in annular or crowded groups, 2-5 mm. across on large, thickened, discolored spots, at first cylindric, 0.5-1.5 mm. high, 0.5-1 mm. in diameter; peridium soon becoming finely fimbriate to base and somewhat twisted or incurved; peridial cells usually seen only in side view, rhomboid, very thick, 30-35 x 60-90 /x, outer wall medium thin, 2-3 /x, smooth, inner wall medium thick, 7-10 /x, rugose, side walls very coarsely rugose with thick, somewhat irregular ridges, roundish or elongate ridge-like papillae inter- spersed; aeciospores globoid, very large, 28-35 x 30-45 fx, wall chestnut-brown, thick, 3-5 /x, rather finely verrucose. 264 PLANT DISEASE FUNGI III. Telia caiilicolous, appearing on hemispheric swelHngs (1-4 cm. long) breaking forth along the sides of the larger branches or on subglobose galls (1.5-2 cm. in diameter) on the smaller branches, applanate, indefinite, usually of considerable size, often covering the whole hypertrophied area, sometimes becoming patelliform when expanded, chocolate-brown; teliospores 2-celled, ellipsoid, 18-28 x 42-61 m, usually slightly narrowed both above and below, slightly or not constricted at the septum, wall cinnamon-brown, 1-1.5 ju thick; pores usually 3 in upper cell, 1 apical, 2 near the septum, in the lower cell 2 pores near the septum. O and I on apple and mountain ash. III. Telia on Juniperus communis and J. sibirica. The teliospores occur on both twigs and leaves. Marked de- formation is caused by this stage on leaves and petioles. G. clavipes C. & P. (=G. germinale [Schw.] Kern) I. ^cia ( = Roestelia aurantiaca) on stems and fruits, crowded on hypertrophied areas of various size on the twigs and peduncles, occupying part or nearly all of the surface of the fruits, cylindric, 1.5-3 mm. high by 0.3-0.5 mm. in diameter; peridium whitish, becoming coarsely lacerate, sometimes to base, erect or spreading; peridial cells seen in both face and side views, polygonal-ovate or polygonal-oblong in face view, 19-39 x 45-95 ^i, rhomboid in side view, 25-40 /jl thick, outer wall moderately thick, 3-5 /x, inner wall very thick, 13-23 /x, coarsely verrucose with loosely set, large, irregularly branched papillae, side walls verrucose on inner half, similar to inner wall; seciospores globoid, large, 31-32 x 24-39 /x, wall pale yellow, thick, 3-4.5 ii, rather coarsely verrucose with crowded, slightly irregular papillae. III. Telia caulicolous, appearing on slight fusiform swellings, usually aggregated, roundish, 1-4 mm. across, often confluent, hemispheric, 1-3 mm. high, orange-brown; teliospores 2-celled, ellipsoid, 18-26 x 35-51 /x, roundish or somewhat acutish above, obtuse below, slightly or not constricted at the septum, wall yellowish, 1-2 /x thick, slightly thicker at the apex; pedicles caroti- form, 9-19 /x in diameter near the spore; pores one in each cell, apical in the upper, near the pedicel in the lower. I. ^cia on Amelanchier, Aronia, hawthorn, quince, and apple. III. Telia on Juniperus communis and J. sibirica. G. nidus-avis Thaxt. I. ^cia amphigenous, especially fructicolous, cylindric, 2-4 mm. PLANT DISEASE FUNGI 265 high by 0.4-6.7 mm. in diameter; peridium soon becoming irregu- larly lacerate, usually to base, slightly spreading; peridial cells seen in both face and side views, lanceolate in face view, 15-23 x 55-88 fjL, linear in side view, 14-18 /x thick, outer wall, 1.5 ^ thick, smooth, inner and side walls 5-7 m thick, coarsely rugose with narrow ridges, with shorter, often roundish papillae inter- spersed; seciospores globoid or broadly elKpsoid, 18-23 x 23-28 fx, wall cinnamon-brown, rather thick, 2.5-4 /x, very finely verrucose, appearing almost smooth when wet. III. Telia cauUcolous, often dwarfing the young shoots and causing bird's nest distortions or witches' brooms, usually causing a reversion of the leaves to the juvenile form, sometimes appearing on isolated areas on the larger branches and producing gradual enlargements, solitary or rarely confluent, of variable size and shape, roundish to oval on the young shoots, 1-2 mm. across, oval to nearly elHptic on the woody branches, 1.5-3 mm. wide by 2-7 mm. long, pulvinate when young, becoming hemispheric, dark reddish-brown; teliospores 2-celled, ellipsoid, 16-23 x 39-55 jjl, wall pale cinnamon-brown, rather thin, 1-1.5 /jl, very slightly thicker at apex; pores one in a cell, apical. Mycelium perennial in leaves, branches or trunks of Juniperus virginiana, very com- monly inducing a "bird's nest" distortion. I. iEcia on Amelanchier and quince. III. Telia on Juniperus virginiana. G. blasdaleanum (D. & H.) Kern occurs on the pear, apple and quince. Uromyces linger (p. 255) 0. Pj^cnia spherical with minute ostioles. 1. iEcia with peridia, spores without pores. II. Urediniospores generally with many germ pores, unicellular, spherical, ellipsoid or variously shaped, usually rough. III. Teliospores unicellular, pedicellate, with an apical germ pore. The unicellular teliospores may be distinguished from unredinio- spores by their single apical germ pore, also usually by their thicker walls and absence of the roughness so characteristic of urediniospores. The genus is a very large one with hundreds of species which ex- hibit heteroecism, autcecism, biologic specialization and the various types regarding spore forms that are noted on pages 231-235. 266 PLANT DISEASE FUNGI U. appendiculatus (Pers.) Fries I. iEciospores angularly globose, whitish, slightly punctulate, 17-32 X 14-20 fjL. II. Urediniospores pale-brown, aculeolate, 24-33 X 16-20 jjL. III. Telisopores elliptical or subglobose, smooth, dark-brown, apex much thick- ened, with a small, hyaline, wart- like papilla, 26-35 x 20-26 /x. An autoecious eu-type. On Phaseolus, Dolichos and other related legumes. The sori usually appear late in "<yi / K J) E L i. a f'ii. N ju ;P~- 0 F "■■-A G H J fV m 0 Q g V I? s Fig. 274. — Stages in the development of the basidium (Agaricus): original binucleate con- dition followed (E-F) by fusion,' and subsequent mitosis N-R, resulting in four spore nuclei. After Wager, PLANT DISEASE FUNGI 283 Will. c m --^ quently covers the surface of gills, pores or spines (Hymeno- mycetes). This is a very large order of over eleven thousand species. The mycelium grows to long distances over or through the sup- porting nutrient medium, often forming conspicuous long-lived resistant rhizomorphic strands or sheets, sometimes developing sclerotia or again appearing as a mere floccose weft. The basidia bear four simple spores, in rare cases two, six or eight. Other forms of spores are found in some species and chlamj^dospores may be borne either externally on the sporophore, in the hymenium, or inside of the sporophore tissue. In the lowest forms the basidia arise directly from the mycelium without the formation of any definite sporo- phore but in most spe- cies the sporophore is highly complex, consist- ing of large, stalked or sessile, pseudoparen- chymatous structures toad-stools, mushroom, etc., on special sur- faces of which, the hy- menium. Fig. 276, hes, covering gills or spines or lining pits or pores. The general relation of the basidia to the hymenium and the sporophore is shown in Fig. 276. Families are delimited by the character of the sporophore, distribution of the hymenial sur- faces, presence of cystidia, size and color of spores, and other more minor points. In germination the spore produces a germ tube which develops directly into a mycelium. In many species the young mycelium is conidia-bearing. Cytologically the group conforms to the general description given on page 281. ■C*A - - nac FiQ, 275. — An agaric (Amanita) sporophore showing parts; c, pileus; m, striated margin; g, gills; a, annulus; s, stem; V, volva; mc, mycelium. After Peck. 284 PLANT DISEASE FUNGI The Agaricales are chiefly of interest to pathologists as wood fungi though in a comparatively few instances they are found on herbs. Upon wood they may do harm. First, as root parasites, in which case death may follow through interference with absorp- tion or anchorage. Second, as causes of heart rots leading to weakness and eventual overthrow of the tree. Third, as parasites of sap wood, cambium or bark lead- ing to death of a part of the host and often its complete loss. In many instances the fungus draws its subsistence from host cells not actually alive and hence strictly speaking they are sapro- phytes. Nevertheless, since their ultimate effect upon the tree is to cause disease or death, from the practical viewpoint these fungi are pathogenic. Many species, more- over, can start their career on a host plant as saprophytes and after attaining a stage of vigorous vege- tative growth become truly para- sitic. In most instances they are wound parasites, which cannot gain access to the inner portions of the host through uninjured tis- sue but must make entrance Fig. 27G.— Cross section of the gill show- thrOUgh SOme WOUUd, aS thoSC duC ing basidia, stengmata and spores, also ^ . . a cystidium stretching from one gill to tO hail, wlud, SUOW, InSCCtS, man the next. After Buller. i , i • , and other annnals. Within the tissues the mycelium may cause the disappearance of substances, e. g., Fomes igniarius consumes the tannin, or the mycelium may secrete enzymes which penetrate the host to long distances. These may dissolve first one component of the cell, e. g., the lignin, next the most lignified residue, the middle lamella, resulting in dissolution of the tissue. In other cases the parts of the cell walls other than the middle lamella are first affected and soon shrink, resulting in cracks. Fig. 279. Some fungi cause char- PLANT DISEASE FUNGI 285 S3 TO 52 Q, 0) s -M a c o 3 O >i >> a -3 a-Q a • "" § "^ a> ex ^^ 4) > tn tn a; > c3^ a=^ ,2 fl 4) fl o to 73 ro *^ ate-- ^3 «• O &.0 .2- > S 3 _ +^ S S o ^ .-Ih •>-( 3-Q 03 O =r 73 4) ^^ „ t- a o— I 03-3 """a; T3 0? o a T3 o 73 43 O sag O 22^ O 73 43 73 a> 03-^ C Oi 03 a 03 43 ^ M c3 - 4) +i fl O 73 — O 03 4) 03 a o a p a C3 71 3 o 43 a 3 ^C £« 43 41 ""< -a. a- 43"^ ■sa ^a -a cj -3 43 03 73 a 'S o 03 43 H - 15 03 ^ 43 . o3.ii *^-43 a; CO >.> c3 4) 43 a a c3 a o ^ 73^ f- ?^ a is ^ « 3 73 73 = 4; 03 g J2 4) i» ^ " i o Ma 73 3 43 . -f^ O 43 a 03 03 a a 03 73 73 -a 73 +J 03 ^S T3 43 a -1-^ o3 a _ ^t3 -a 73 43 43 03 a ^ a 43 — , O 41-3 ^^-^^ !3 ~ ^ "3 03 -O O o o3 I-, 73 73 -tJ a -^^ 2 1=1 != 03 o; O - « a a^ 03 73 43 O 73 "^^^ 03 a ° >--T-, ^ 43 S3 a fO 55 03 *^ o3 a-«. ^a-3 ^'-1 a • l-H , W C3 CD -*^ CQ vy -*-■ H4 iwi ^ CD cd s_,^ a s - : y3 a 3 0, ^-a^ o3^X! b 03-3 1.73 . 4) .iS G o i> ^-o a2 3 03 t^^ 4; « -^ 03 71 2 e^'c ^ 4) a --= El 03 03 ^a 43 — 0;s aH SL:;ti;-2 ■s a-- " O ~ u 0) S u 73 a O .£2 ."5 "3 o xi o Li 0) O 2 cm.; surface smoky, covered with a thin, separating pellicle, glabrous, devoid of markings, cracking with age; margin velvety, concolorous, obtuse, projecting nearly a centimeter beyond the hymenium; context fleshy-tough, elastic, homogenous, 3 cm. thick, milk-white; tubes 0.5 cm. long, 2-3 to a mm., sodden-white, sepa- 304 PLANT DISEASE FUNGI rated from the context by a thin pink layer; mouths very irregular, dissepiments thicker than the pores, obtuse, entire, crumbling away in age, leaving the smooth, white context; spores white, cylindrical, curved, 4-5 /x in length. The mycelium penetrates lignified cell walls entering the living cells and causing death. On birch it causes a decay of the sap wood similar to that caused by Fomes fomentarius. P. adustus (Wild.) Fr. is a common saprophyte of deciduous trees. Numerous other species occur on oak, larch, chestnut, chinqua- pin, poplar, spruce, fir, juniper and many other conifers and decid- uous trees. Polystictus Fries (p. 296) Sporophore leathery, usually thin; pores developing from the center to the circumference of the hymenophore. The thicker forms are quite close to some species of Polyporus. About four hundred fifty species. P. versicolor (L.) Fr. Pileus densely imbricate, very thin, sessile, dimidiate, conchate, 2-4 X 3-7 X 0.1-0.2 cm.; surface smooth, velvety, shining, marked with conspicuous, glabrous zones of various colors, mostly lateri- ceous, bay or black; margin thin, sterile, entire; context thin, mem- branous, fibrous, white; tubes punctiform, less than 1mm. long, white to isabelline within, mouths circular to angular, regular, even, 4-5 to a mm., edges thick and entire, becoming thin and den- tate, white, glistening, at length opaque-isabelline or slightly um- brinous; spores allantoid, smooth, hyaline, 4-6 x 1-2 /x; hyphse 2- 6 /i; cystidianone. Von Schrenk regards this as strictly a saprophyte except when on catalpa, where it causes a heart-rot. It is common on almost any kind of wood. Catalpa wood under its action becomes straw-colored and finally soft and pithy. Both cellulose and lignin are dissolved. P. sanguineus (L.) Fr. and P. cinnabarinus (Jacq.) Fr. are sapro- phytes on dead parts of live trees. P. velutinus (Pers.) Fr. is a common saprophyte which is per- haps sometimes parasitic. P. pergamenus Fr. Pileus exceedingly variable, sessile or affixed by a short tubercle, dimidiate to flabelliform, broadly or narrowly attached, 2-5 x 2-6 PLANT DISEASE FUNGI 305 X 0.1-0.3 cm.; surface finely villose-tomentose, smooth, white or shghtly yellowish, marked with a few narrow indistinct lateri- ceous or bay zones; margin thin, sterile, entire to lobed; context very thin, white, fibrous; tubes 1-3 mm. long, white to discolored within, mouths angular, somewhat irregular, 3^ to a mm., usually be- coming irpiciform at an early stage, edges acute, dentate, becoming lacerate, white to yellow- ish or umbrinous; spores smooth, hyaline. It causes a sapwood rot of practically all spe- cies of deciduous trees, often on dead trees, less frequently on living trees which have been severely injured. In general the rotten wood resembles that produced by P. versicolor; microscopically it is seen that the fungus attacks chiefly the lignin. P. hirsutus Fr. Pileus confluent-effused, more or less imbricate, sessile, dimid- iate, applanate, corky-leathery, rather thick, flexible or rigid, 3-5 X 5-8 X 0.3-0.8 cm.; surface conspicuously hirsute, isabelline to cinereous, concentrically furrowed and zoned; margin at length thin, often fuliginous, sterile, finely strigose-tomentose, entire or undulate; context white, thin, fibrous, spongy above, 1-4 mm. thick; tubes white, 1-2 mm. long, mouths circular to angular, 4 to a mm., quite regular, edges thin, firm, tough, entire, white to yellowish or umbrinous; spores smooth, hyaline, cylindrical, slightly curved, 2.5-3 ix. On deciduous trees and conifers; a wound parasite of the mountain ash. '^j'l^-f^' \:'^.^'"/-':^i'^-'^^^tlBIS>' aS^'^i: ^"^t^ •,^c^:-^"iufe .^\ <^**5t lis- 'Xi^K ;*;- 1^ ^J^^K i ^IS l»llfti Fig. 292. — Polystictus pergamenus. After Freeman. Femes Fries (p. 296) Sporophore sessile, ungulate or applanate; surface varnished, encrusted, sulcate, vinose, or anoderm, rarely zonate; context 306 PLANT DISEASE FUNGI corky to punky; tubes cylindric, stratiose; spores smooth, hyaline or brown. A genus of some three hundred species. F. igniarius (L.) Gill. Pileus woody, ungulate, sessile, 6-7 x 8-10 x 5-12 cm. ; surface smooth, encrusted, opaque, velvety to glabrous, ferruginous to fuscous, becoming rimose with age; margin obtuse, sterile, fer- ruginous to hoary, tomentose; context woody, distinctly zonate, ferruginous to fulvous, 2-3 cm. thick; tubes evenly stratified, 2-4 mm. long each season, fulvous, whitish-stuffed in age, mouths circular, minute, 3-4 to a mm., edges obtuse, ferruginous to ful- FiG. 293. — Fomes igniarius, from maple. After Atkinson. vous, hoary when young; spores globose, smooth, hyahne, 6-7 /x; spines 10-25 x 5-6 /jl. It is the cause of a white heart-rot, one of the most widely dis- tributed forms of wound parasites, and occurs on more species of broad-leaf trees than any other similar fungus. Among its hosts are beech, oak, apple, peach, willow, aspen, the maples, birch, butternut, walnut, hickory, alder. The first sporophores usually appear at the point of initial infection. The mycelium grows mainly in the heart wood but it may gain entrance through the sap wood or encroach upon the sap wood from the heart wood. Its growth may continue after the death of the host. In early stages it follows the medullary rays. The completely rotted wood is white to light yellow and in it the mycelium abounds in the large vessels and the medullary PLANT DISEASE FUNGI 307 rays. The walls of the affected wood cells are thin and the middle lamella is often wholly lacking, due to solution of the lignin. F. fomentarius (L.) Fr. Pileus hard, woody, ungulate, concave below, 7-9 x 8-10 x 3-10 cm. ; surface finely tomentose to glabrous, isabelline to avellaneous Fig. 294. — A dead beech tree with sporophores of F. fomentarius. von Schrenk and Spaulding. After and finally black and shining with age, zonate, sulcate, horny- encrusted; margin obtuse, velvety, isabelline to fulvous; context punky, homogeneous, ferruginous to fulvous, conidia-bearing, 3-5 mm. thick; tubes indistinctly stratified, not separated by lay- ers of context, 3-5 mm. long each season, avellaneous to umbrinous within, mouths circular, whitish^stuff ed when young, 3-4 to a mm. ; 308 PLANT DISEASE FUNGI edges obtuse, entire, grayish-white to avellaneous, turning dark when bruised; spores globose, smooth, very hght brown, 3-4 fx; hyphse brown, 7-8 /x; cystidia none. The mycehum kills the cambium and causes a white rot of the sap wood of deciduous trees, especially beech, birch, elm, maple, reported also on apple. The wholly rotted wood is soft and spongy, light yellow and crumbles into its separate fibers. F. everhartii E. & G. (=Pyropolyporus prserimosa) Pileus woody, dimidiate, ungulate, broadly attached behind, 6-10 X 6-15 X 3-8 cm.; surface glabrous, slightly encrusted, deeply sulcate, not polished, gray to brownish-black, slightly rimose in age; margin obtuse, covered with ferruginous tomentum, becoming gray and glabrous; context corky to woody, repeatedly zoned, fulvous in dried specimens, 2-3 cm. thick; tubes evenly stratified, 0.5-1 cm. long each season, fulvous, mouths circular, 4 to a mm.,, edges rather thin, entire, ferruginous to fulvous, glistening, the hymenium becoming much cracked in age; spores globose, smooth, ferruginous, 3-4.5 jj,; spines abundant, pointed, larger at the base, 15-25 x 6-10 ju. On black oaks and walnuts causing a rot almost indistinguish- able from that caused by F. igniarius. The mycelium often grows into the living sap wood. F. carneus Nees Pileus woody, dimidiate, varying from conchate to ungulate, often imbricate and longitudinally effused, 2-4 x 6-8 x. 0.5-3 cm.; surface rugose, subfasciate, slightly sulcate, rosy or flesh-colored, becoming gray or black with age; margin acute, becoming obtuse, sterile, pallid, often undulate; context floccose-fibrose to corky, rose-colored, 0.2-2 cm. thick; tubes indistinctly stratose, 1-2 mm. long each season, mouths circular, 3-4 to a mm., edges obtuse, concolorous; spores ellipsoid, smooth, thick-walled subhyaline, 3.5 X 6 /z. On red cedar and arbor vitse causing pockets, also on dead spruce and fir. The cellulose is almost all removed from the affected cells of the heart wood. The mycehum is scant and when young is pale and with numerous clamps. It extends horizontally through the tracheids, giving off lateral branches. None is found in the sap wood. F. annosus (Fr.) Cke. (=Trametes radiciperda R. Hartig) Pileus woody, dimidiate, very irregular, conchate to applanate, 10-13 x 5-8 X 0.5-2 cm.; surface at first velvety, rugose, anoderm. PLANT DISEASE FUNGI 309 light brown, becoming thinly encrusted, zonate, and finally black with age; margin pallid, acute, becoming thicker; context soft- corky to woody, white, 0.3-0.5 cm. thick; tubes unevenly stratified, 2-8 mm. long each season, white, mouths subcircular to irregular, 3-4 to a mm., edges rather thin, entire, firm, white, unchanging; spores subglobose or ellipsoid, smooth, hyaline, 5-6 x 4-5 fi. On pine, fir and various deciduous trees, including apple, de- scribed by Hartig as the most dangerous of all conifer parasites. It is not so plentiful in America as in Europe. The sporophores appear near or on the roots, between the bark scales, where the white felted delicate mycelium also occurs. The spores, carried presumably by rodents, germinate upon the bark of roots; the mycelium penetrates to the living cortex, forces its way into the wood and follows up the stem and down the root. The parenchyma cells are killed and browned; the wood becomes violet, later brownish-yellow. The hyph2e travel in the cell- lumen and pierce the walls. The lignified parts are dissolved first, later the middle lamella disappears. Eventually the whole root system may become involved and the death of the tree result. F. juniperinus (v. Sch.) S. & Sy. Pileus woody, ungulate, 3-5 x 5-8x5-7 cm; surface tomentose, deeply sulcate, ferruginous to gray, at length rough and grayish- black; margin obtuse, velvety, melleous or ferruginous to hoary; context corky to woody, reddish-fulvous, 0.5-1 cm. thick; tubes indistinctly stratified, 0.5-1 cm. long each season, melleous within, reddish-fulvous in the older laj^ers, mouths circular to angular, 2-3 to a mm., edges rather thin, entire, even, melleous; spores reddish-brown, smooth; spines blunt, only sHghtly projecting. On red cedar. In the holes caused by the fungus in the heart wood is found a velvety mass of reddish-yellow mycelium, glistening with color- less liquid and holding masses of reddish-brown wood fiber. Long white fibers of cellulose with the lignin removed project into the cavities from the ends. Structural change begins soon after the mycelium enters a cell lumen. The primary lamella becomes granular and is dissolved by a lignin-splitting enzyme, the secondary lamella becomes white and the cells fall apart. The mycelium in newly invaded tissue is nearly hyaline and extends lengthwise. Within the tracheids branches are given off in all directions. 310 PLANT DISEASE FUNGI The sporophore appears after decomposition is considerably advanced. F, laricis (Jacq.) Murr. Pileus firm, at length fragile, ungulate to cylindical, 3-8 x 5-10 X 4-20 cm.; surface anoderm, powdery, white or slightly yellow- ish, concentrically sulcate, becoming slightly encrusted, tuberculose and rimose; margin obtuse, concolorous; context soft, tough, at length friable, chalk-white or slightly yellowish, very bitter, with the odor of fresh meal, 1-3 cm. thick; tubes evenly strati- fied, concolorous, 5-10 mm. long each season, mouths circular to angular, 3-4 to a mm., edges thin, fragile, white, becoming dis- colored and lacerate, wearing away with age; spores ovoid, smooth, hyahne, 4-5 ^t; hyphae 5 fx; cystidia none. A wound parasite of the larch, pine and spruce in Europe and America. F. ribis (Schw.) Gill. Pileus tough, corky, becoming rigid, conchate, laterally connate, 3-5 X 5-10 X 0.7-1.5 cm.; surface rough, velvety, anoderm, in- distinctly zoned, ferruginous to umbrinous, becoming glabrous and slightly encrusted with age; margin undulate to lobed, fer- ruginous, furrowed; context punky, fulvous, 3-5 mm. thick; tubes indistinctly stratified, 1-2 mm. long each season, fulvous, mouths circular, 5-6 to a mm., edges rather thin, entire, ferruginous to fulvous, hoary when young; spores globose or subglobose, pale yellowish-brown, smooth, 3-4 x 3 fx; hyphse 2.5 /x; cystidia none. This is a wound parasite on the heart wood of sassafras and is also found on roots and stems of various shrubby plants including rose, gooseberry and currant. The fungus fills the large vessels and tracheids with a brown mycelium and dissolves the entire wall locally. F. fulvus (Scop.) Gill. Pileus woody, triquetrous, rarely ungulate, thick and broadly attached behind, 1-3 x 5-7 x 3-8 cm.; surface smooth, very slightly sulcate, velvety, ferruginous, becoming horny and glabrous and finally nearly ])lack with age; margin subobtuse, ferrugi- nous, velvety; context woody, fulvous, 1-2 cm. thick; tubes evenly stratified, 2-3 mm. long each season, fulvous, mouths circu- lar, 3 to a mm., edges obtuse, entire, ferruginous to fulvous; spores globose, compressed on one side, hyaline, 5.5-6 x 4.5-5 fx; spines fulvous, 15-20 X 7-9 fx; hypha) 2.5 //. On plum, birch and other trees. PLANT DISEASE FUNGI 311 The decayed wood is red-brown and crumbles when crushed. F. nigricans Fr. is very similar to F. igniarius from which it differs chiefly in the black upper surface and the bluish or blackish hymenial surface of the sporophores. As a wound parasite it causes a reddish-brown heart-rot of deciduous trees, especially of willow, birch, poplar, beech. F. fraxinophilus (Pk.) Sacc. Pileus woody, subtriangular, compressed-ungulate, usually decurrent, 5-10 x 6-12 x 2-4 cm.; surface white, pulverulent or finely tomentose, concentrically sulcate, becoming gray or black and rimose with age; margin tumid, white or yellowish, velvety to the touch; context corky to woody, zonate, isabelline, 0.5-1 cm. thick; tubes evenly but indistinctly stratified, 2-4 mm. long each season, white when young, concolorous with the context in the older layers, mouths white, subcircular, 2 to a mm., edges obtuse; spores broadly ellipsoid, smooth, hyaline, thin-walled, 6-7 x 7-8 fjL; hyphse light yellowish-brown, 10-12 ii; cystidia none. It causes a heart-rot of trunk and branches of species of ash. The starch in the host cells is lost early by diastatic action in advance of the fungus, the nearest hyphse of which may be several millimeters distant, and is replaced by a decomposition product. The mycelium advances through the medullary rays and spreads through spring and summer bands, abstracting the lignin; the middle lamella dissolves and the cells fall apart. Completely rotted wood is straw-colored, very soft, non-resistant. The young hyphse are very fine and require an immersion lens for observation. Clamp connections are frequent. The sporophore appears after the destruction of the wood is considerably advanced. F. robiniae (Murr.) S. & Sy. A large fungus with dark rimose surface and tawny hymenium. Pileus hard, woody, dimidiate, ungulate to applanate, 5-25 x 5-50 x 2-12 cm.; surface velvety, smooth, soon becoming very rimose and roughened, fulvous to purplish-black, at length dull- black, deeply and broadly concentrically sulcate; margin rounded, velvety, fulvous; context hard, woody, concentrically banded, 1-3 cm. thick, fulvous; tubes stratose, 0.15-0.5 cm. long, 50 to a mm., fulvous, mouths subcircular, edges entire, equaling the tubes in thickness; spores subglobose, smooth, thin-walled^ fer- ruginous, copious, 4-5 m; cystidia none. On black locust causing heart-rot, arising from wound infection of Uving trees. The very hard wood becomes a soft, yellow to 312 PLANT DISEASE FUNGI brown mass, spongy when wet. The decay extends out in radial lines from the center, alons; the large medullary rays, killing the cambium and bark on reaching them. The lignin is first dissolved, later the cellulose. The fungus ceases growth on the death of its host. F. marmoratus Berk. (=F. fasciatus [Sw.] Cke.) Pileus hard, woody, dimidiate, applanate to ungulate, convex above, 7-10 x 8-15 x 2-6 cm.; surface finely tomentose, at length glabrous, concentrically sulcate, at first mole-colored, changing to umbrinous, and finally avellaneous with black fasciations ; margin acute to obtuse, isabelline, sterile, undulate or entire; context punky, thin, ferruginous to fulvous, zonate, 3-5 mm. thick, tubes indistinctly stratified, 5-10 mm. long each season, avellaneous within, mouths circular, minute, 4-5 to a mm., edges obtuse, avellaneous to umbrinous, becoming darker when bruised ; spores subglobose, smooth, light brown, 5-7 ix; hyphse brown, 4-6 /x; cystidia none. On water oak and orange, especially abundant on the former. F. sessilis (Murr.) Sacc. A variable fungus with wrinkled varnished cap and acute margin, found on decaying deciduous trees. Pileus corky to woody, dimidi- ate, sessile or stipitate, imbricate or connate at times, conchate to fan-shaped, thickest behind, thin at the margin, 5-15 x 7-25 X 1-3 cm.; surface glabrous, laccate, shining, radiate-rugose, con- centrically sulcate, yellow to reddish-chestnut, at length opaque, dark-brown, usually marked near the margin with alternating bay and tawny zones; margin usually very thin and acute, often curved downward, often undulate, rarely becoming truncate, white, at length concolorous; context soft-corky or woody, radiate- fibrous, concentrically banded, ochraceous-fulvous; tubes 0.52 cm. long, 3-5 to a mm., brown within, mouths circular or angular, white or grayish-brown, edges thin, entire; spores ovoid, obtuse at the summit, attenuate and truncate at the base, verrucose, yellowish-brown, 9-11 x 6-8 ju; stipe laterally attached, usually ascending, irregularly cylindrical, 1-4 x 0.5-1.5 cm., resembling the pileus in color, surface and substance, often obsolete. It occurs on oak and maple as a wound parasite, destroying bark and cambium. This and related species are usually saprophytic. F. pinicola Fr. Pileus corky to woody, ungulate, 8-15 x 12-40 x 6-10 cm.; surface gla))rous, sulcate, reddish-brown to gray or ])lack, often PLANT DISEASE FUNGI 313 resinous; margin at first acute to tumid, pallid, becoming yellowish or reddish-chestnut; context woody, paUid, 0.5-1 cm. thick; tubes distinctly stratified, 3-5 mm. long each season, white to isabel- line, mouths circular, 3-5 to a mm., edges obtuse, white to cream-colored; spores ovoid, smooth, hyaline, 6 fx; hyphse 8 /z; cystidia none. It occurs on conifers; pine, hemlock, spruce, balsam, larch, etc., more rarely on beech, birch and maple, as a wound parasite of the heart wood. The sporophores are often ab- sent until after death of the host. The tracheids bear many holes. The wood carbonizes, the cellulose is destroyed and sheets of my- celium form, particularly within the space occupied by the medullary rays and in tangential crevices. Fig. 295. F. applanatus (Pers.) Wallr. Pileus hard, woody, dim- idiate, applanate, 6-15 x 8-30 x 1-4 cm.; surface milk-white to gray or umbrinous, glabrous, concentrically sulcate, encrusted, fasciate with obscure lines, conidia-bearing, usually brownish during the growing season from the covering of conidia; margin obtuse, broadly sterile, white or slightly cremeous, entire to undu- late; context corky, usually rather hard, zonate, fulvous to bay, 5-10 mm. thick, thinner with age; tubes very evenly stratified, separated by thin layers of context, 5-10 mm. long each season, avellaneous to umbrinous within, mouths circular, 5 to a mm., whitish-stuffed when young, edges obtuse, entire, white or slightly yellowish to umbrinous, quickh' changing color when bruised; spores ovoid, smooth or very slightly roughened, pale yellowish- brown, truncate at the base, 7-8 x 5-6 fx. It is described as the cause of rot of both heart and sap wood of living cotton-wood trees. The invaded medullary rays first Fig. 295. — F. pinicola growing on dead trunk of western hemlock. After von Schrenk. 314 PLANT DISEASE l^UNGI lose their starch by digestion. Next the Hgnin is dissolved, then the cellulose. Fig. 296. — Fomes applanatus. After Freeman. Trametes Fries (p. 296) Sporophore annual, rarely perennial, sessile; context homo- geneous, coriaceous to corky, extending between the tubes, which are circular or irregular. There are about one hundred fifty species. T. pini (Thore) Fr. Pileus hard, woody, typically ungulate, conchate or effused- reflexed in varieties, often imbricate, 5-8 x 7-12 x 5-8 cm., smaller in varieties ; surf ace very rough, deeply sulcate, tomentose, tawny- brown, becoming rimose and almost black with age; margin rounded or acute, tomentose, ferruginous to tawny-cinnamon, en- tire, sterile in large specimens : context soft-corky to indurate, homo- geneous, ferruginous, 5-10 mm. thick, thinner in small specimens; tubes stratified, white to avellaneous within, becoming ferrugi- nous at maturity and in the older layers, 5 mm. long each season, much shorter in thin specimens; mouths irregular, circular or dsedaleoid, often radially elongate, averaging 1 to a mm., edges ferruginous to grayish-umbrinous, glistening when young, rather thin, entire; spores subglobose, smooth, hyaline at maturity, becoming brownish with age, 5-6 x 3-4 /z; spines abundant, short, 25-35 X 4-6 fx. PLANT DISEASE FUNGI 315 It occurs on pine, spruce, larch, hemlock, and fir as a wound parasite of the heart wood; it is also on willow and birch. The spores are wind-borne and, lodging on unprotected sur- faces, develop a mycelium which grows both up and down, spread- ing most rapidly in a longitudinal direction, or horizontally follow- ing an annual ring. The fungous enzyme first dissolves the lignin leaving the individual tracheids free and of nearly pure cellulose. The cellulose is later dissolved, resulting in holes in the wood. It is found on most of the conifers of the United States as a sapro- phyte. The wood becomes white-spotted. In late stages of decay the entire wood is full of small holes which are lined with a white fungous felt. T. suaveolens (L.) Fr. Pileus large, subimbricate, dimidiate, sessile, convex above, plane or concave below, 4-6 x 5-12 x 1-3 Cm.; surface smooth, anoderm, azonate, finely villose-tomentose to nearly glabrous, white to pale-isabelline; margin thick, sterile, entire; context white, punky-corky, 1-2 cm. ^- .~^-,^ thick, very fragrant when fresh, y^' ^ "^ . with the odor of anise; tubes 5- 15 mm. long, white within, \ mouths circular, 2 to a mm., edges at first very thick, white, "f"- entire, becoming thinner and often blackish with age; spores oblong-ovoid, subsinuate, smooth, hyaline, 8-9 x 3-5 /x; hyphae 7 ii\ cystidia none. On willow and poplar. Favolus Fries (p. 296) Fig. 297. — Favolus europseus. After Lloyd. Sporophore leathery, fleshy, or coriaceous, laterally stipitate; hymenium with large elongated pores which may even become lamellate, Fig. 297. A genus of some seventy species. F. europaeus Fr. is a parasite of fruit and nut trees. ;3i() PLANT DISEASE FUNGI Daedalea Pcrsoon (}). 296) Hymenophore epixylous, usually large and annual, sessile, applanate to ungulate; surface anoderm, glabrous, often zonate; context white, wood-colored or brown, rigid, woody, tough or punky; hymenium normally labyrinthiform, but varying to lamel- late and porose in some species; spores smooth, hyaline. About seventy-six species. Fig. 298. D. quercina (L.) Pers. Pileus, corky, rigid, dimidiate, sessile, imbricate, applanate, convex below, triangular in section, 6-12 x 9-20 x 2-4 cm.; surface isabelline-avellaneous to cinerous or smoky-black with age, slightly sulcate, zonate at times, tuberculose to colliculose in the older Fig. 298. — Daedalea quercina on oak. After von Schrenk and Spaulding. portions; margin usually thin, pallid, glabrous; context isabelline, soft-corky, homogeneous, 5-7 mm. thick; tubes labyrinthiform, becoming nearly lamellate with age in some specimens, 1-2 cm. long, 1-2 mm. broad, chalk-white or discolored within, edges obtuse, entire, ochraceous to avellaneous. Common on oak, maple and chestnut, often on living trees but growing only on the dead wood. PLANT DISEASE FUNGI 317 Lenzites Fries (p. 296) Hymenophore small, annual, epixylous, sessile, conchate; surface anoderm, usually zonate and tomentose; context white or brown, coriaceous, flexible; hymenium lamellate, the radiating gill-like dissepiments connected transversely at times, especially when young; spores smooth, hyaline. Fig. 299. About seventy-five species. Fig. 299. — Lenzites betulina. After Freeman. L. abietina (Bui.) Fr. occurs on firs. L. sepiaria (Wulf.) Fr. has been reported as a parasite on conifers and deciduous trees. L. vialis Pk. and L. betulina (L.) Fr. are common saprophytes on deciduous trees, perhaps also parasitic; L. variegata Fr. occurs on beech and poplar. 318 PLANT DISEASE FUNGI Agaricaceae (p. 286) Sporophores usually fleshy, rarely coriaceous or leathery, stip- itate or shelvmg; stipe variable in development, lateral or central, annulate or not, the entire young sporophore often volvate at first ; hymenium lamellate, the lamellae usually free, rarely anastomosing, sometimes dichotomous, rarely reduced to ridges or slight folds. A family of over twelve hundred species. Key to Tribes of Agaricaceae Hymenium with normally developed gills; lamellae not fleshy or waxy; substance of the pileus of only one kind of hyphse Sporophore at maturity leathery or corky, persistent, rarely fleshy Lamella} at maturity split lengthwise. . . 1. Schizophylleae, p. 318. Lamellse at maturity not splitting 2. Marasmieae, p. 319. Sporophore at maturity fleshy, finally putrescent 3. Agariceae^ p. 320. Schizophylleae Sporophore, leathery, persistent, the cleft gills with recurved margins. Schizophyllum Fries Cap woolly, upturned, sessile, epixylous; gills cleft, the margins recoiled; texture leathery. Fig. 300. — S. aineum. After Atkinson. . About twelve species. Fig. 300. S. aineum (L.) Schr. Cap 1-4 cm. wide, white or gray-woolly, upturned, attached excentrically, irregularly saucer-shaped, stem lacking; gills grayish to purplish; spores subglobose, 2-3 /x. PLANT DISEASE FUNGI 319 It parasitizes sugar-cane, horse chestnut, chestnut, mulberry and orange. Marasmieae (p. 318) Pileus tough, leathery, thin, membranous, or rarely somewhat fleshy, reviving after drying with the return of moisture. About five hundred fifty species. Key to Genera of Marasmieae Gills leathery; spores hyaline Pileus not distinct from the stipe; sporo- phore trumpet-shaped; gills with a thin edge, toothed on the margin 1. Lentinus, p. 319. Pileus distinct from the stipe; annulus wanting; pileus firm and dry 2. Marasmius, p. 320. Lentinus Fries Sporophore trumpet-shaped, pileus and stipe not distinct, leathery, pileus central or lateral, gills toothed; spores white. About three hundred fifty species. "■•'"M 0 m ■ ■ flfe^V'V.^^^ m^^. W^F^^n^- '^'^^H ^^^^4^^^^^^iJDk ' ^ ^^"^ ^'^ ^^ ^ ^^^^^^^^^^ ^^^Hh^^^^^It^^"!bEs9b^jI^^ 'if '! ^s'wS^B^^S^^^^^^KK^^^^^ ^^^^^■^''^^■^^B!^^'^ '*^/^^^^^M ij^m^Mpi^B ^^BJgggJPP^w^^^^^^lMfa^q^^apiM ^^^^Kim^^^BBB^^KK^'^'t^ it--^^ , JH^^^^^^^^^BH^HBmj^mMBKBIII^m^^B ^^B9H^^9l^H^?''^''^X'^^ll9^ESB^^^^9H^^^i^^^^B'9BHl ^^^^^^Mh^^^^ShIhhH WS^^^OSff^^S^K^Kii S^r -"'"'^^ ' **w^ ' ■ '--'t^^' "^^^'■' y;.jA,.^,ga^ ^S&. ^I^yl^%^ Fig. 301. — Lentinus lepideus. After Hard. 320 PLANT DISEASE FUNGI L. conchatus (Bui.) Schr. is found on birch, poplar, aspen. L. lepideus Fr. on pine, birch, etc. Marasmius Fries (p. 319) Sporophore tough, withering, often reviving in renewed mois- ture; pileus, with few exceptions, regular, thin, leathery, without a veil, sharply differentiated from the stipe, rarely sessile or laterally attached; stipe tough, cartilaginous or horny, without an annulus; gills tough, thin, leathery or membranous, entire margined. Some four hundred fifty species of wide distribution, but chiefly small tropical fungi. M. plicatus Wak. Pileus submembranous, convex or subcampanulate, glabrous, sulcate-striate, chestnut or light wine-colored; gills rather distant, white, basally attached; stipe slender, glabrous above, white, downy below. This fungus which exists first as a saprophyte resides primarily in the soil from which it grows over the stools of sugar-cane and eventually penetrates living tissue, destroys many roots and smothers the developing buds. The white mycelium is found cementing the lower leaf sheaths to the cane. It is probable that several species are concerned. Agariceae (p. 318) This tribe contains all the gill fungi and is characterized by a fleshy, putrescent sporophore; gills fleshy, rarely tough or leathery, weak, easily broken, not deliquescent, without milky juice. It is the largest tribe of the family. The genera are conveniently grouped as black, brown, rusty, pink or red, and white-spored forms. None of the black-spored species are known as parasites. Phaeosporeae (Rusty-spored series) Annulus continuous; veil single, forming the annulus 1. Pholiota, p. 323. Rhodosporeae (Pink-spored series) Stipe central ; volva present, annulus wanting 2. Volvaria, p. 323. Volva and annulus both wanting; gills free from the stipe 3. Pluteus, p. 324. PLANT DISEASE FUNGI 321 FiQ. 302. — Marasmius plicatus. After Fulton. 322 PLANT DISEASE FUNGI Leucosporeae (White-spored series) Stipe lateral, or none 4. Pleurotus, p. 324. Stipe central Volva absent; annulus present; gills united to the stipe; pileus usually smooth ... 5. Armillaria, p. 326. Volva and annulus both absent Gills decurrent on the stipe; stipe fleshy. 6. Clitocybe, p. 327. Gills adnate, stipe with a cartilaginous rind 7. Collybia, p. 328. Gills sinuate ; stipe with a cartilaginous rind; pileus membranous, more or less striate 8. Mycena, p. 329. Fig. 303. — Pholiota adiposa. After Freeman. PLANT DISEASE FUNGI 323 Pholiota Fries (p. 320) Pileus symmetrical, more or less thick, fleshy, with a veil which forms an amiulus; gills adnate, becoming rusty at maturity. Fig. 303. P. aurivilla (Bat.) Quel, and P. squarrosa Miill. occur on decid- uous trees, especially on the apple. P. spectabilis Fr. is occasionally parasitic on oaks. P. mutabilis (Scha.) Quel, is a root parasite on trees. P. adiposa Fries. Cap medium, 5-10 cm. wide, yellow, very sticky when moist, with spreading or erect, rust-brown scales which sometimes dis- appear when old, convex to plane; stem 5-15 x 1-2 cm., yellow, paler above and darker, scaly below the more or less imperfect tufted ring, solid or stuffed; gills adnate, yellowish to rust-colored, broad, crowded; spores rust-colored, elliptic, 7-8 x 5 /x. The name may refer to the sticky cap. Chiefl^^ a saprophyte, occasionally on living trees, both deciduous trees and conifers, as a wound parasite. P. destruens Broud. occurs on poplar; P. cervinus Scha. on various trees. Volvaria Fries (p. 320) Fleshy, gills free, white, later pink; spores ellipsoid, smooth; annulus none; volva present. Easily distinguished from all other pink-spored genera by the volva. Fig. 304. About thirty-six species. V. bombycina (Scha.) Quel. Cap large, 8-25 cm. wide, all white and silky, more rarely somewhat scaly, hemispheric or bell-shaped to convex; stem 8-12 x 1-2 cm., white, smooth, tapering upward, solid, volva large and spreading; gills free, salmon-pink, crowded, spores elliptic, 6-7 X 4 ju. It is often parasitic on various trees. Fig. 304. — Volvaria bombycina. After Atkinson. 324 PLANT DISEASE FUNGI Pluteus Fries (p. 320) Pileus fleshy, regular, separating easily from the stipe; gills free; volva and annulus both absent; spores elliptic. P. cervinus Scha. Fig. 305. Cap large, 5-16 cm. wide, usually some shade of brown, from grayish or yellowish to blackish-brown, more or less fibrous or hairy on the disk, sometimes sticky, convex or plane; stem 7-15 Fig. 305. — Pluteus cervinus. After Atkinson. X 3^-1 cm., brownish, smooth or black-hairy, solid; gills free, pink, broad; spores pink, rarely greenish, globoid, 7-8 x 5-6 n. A common saprophyte which is occasionally parasitic. Pleurotus Fries (p. 322) Pileus laterally sessile or excentrically stipitate. Fig. 306. A genus of about two hundred fifty species. P. ostreatus Jacq. Cap large, 7-24 cm. wide, white, gray or tan, smooth or more or less scaly in age, convex or plane, shelf or shell-shaped, more or less lobed and torn at the margin; stem short and lateral, or none, white, solid, more or less hairy at base; gills long-decurrent, con- nected by veins on the stem, white or yellowish; spores elliptic, 8-10 X 4-5 M- Common on deciduous trees, mainly saprophytic. PLANT DISEASE FUNGI 325 P. salignus Schrad. is often parasitic on willow, poplar, mul- berry, etc. P. ulmarius Bui. Cap large, 8-15 cm. wide, white, whitish or tan, often brownish toward the center, smooth, often cracked, usually convex, some- times plane; stem long and stout, often nearly central, 5-12 cm. Fig. 306. — Pleurotus ostreatus. After Clements.- by 2-3 cm., white or tan, smooth or hairy toward the base, solid, elastic, often curved; gills annexed or sinuate, whitish, broad, close; spores globose, 5-6 ix. Parasitic on elm and maple or usually a saprophyte. Other questionable parasites are: P. atrocoeruleus Fr. on willow; P. mitis Pers. on pine; P. corticatus Fr. on poplar. 326 PLANT DISEASE FUNGI Armillaria Fries (p. 322) Fleshy, the substance of the pileus and stipe continuous; annu- lus fixed; gills usually attached, white; spores clavate, ellipsoid or ovate, smooth. About sixty species. Fig. 308. A. mellea (Vahl) Quel. Cap large, 3-15 cm. wide, usually honey-colored, but varying through all shades of yellow to brown, typically marked with small tufts of brownish or black- ish hairs, especially toward the center, though sometimes woolly or entirely smooth, margin often striate, convex to expanded; stem tall, stout, 3-15 cm. by 6- 20 mm., whitish, yellowish, or brownish, especially below the ring, smooth or scaly, hollow or stuffed, ring usually thickish and conspicuous, but sometimes thin or even lacking; gills touch- ing broadly or running down the stem, whitish or yellowish; spores elliptic or rounded, 7- 10 M. This is a common wound par- asite of conifers and deciduous trees, causing a root-rot, espe- cially important on apple, peach, cherry, plum, also on Rubus. It is also reported as the cause of a potato root-rot. The abundant mycelium is white and extends a meter or more through the wood and bark, aggregating under or on the bark to form shining, hard, gray-black, intertangled cords, rhizomorphs, 1-2 mm. in diameter often reaching out to great distances through the earth. Fig. 307. Sheets of white felt also occur. The young mycelium grows into the cambium layer, attacking living cells and often encircling the tree. In the living cortex it presents a characteristic fasciated skin-like appearance. The sporophores are borne in clusters in autumn on the ground or on the bark. Fig. 307. — Rhizomorphs of A. mellea. After Freeman. PLANT DISEASE FUNGI 327 The spores, sown in plum decoction, develop a mycelium which soon produces rhizomorphs. These advancing give off delicate hyphae which may penetrate into the host. The mycelium spreads Fig. 308. — Armillaria mellea. After Wilcox. most rapidly through the medullary rays and from them into other tissue elements. A. mucida (Schrad.) Quel, is reported as a wound parasite of the beech. Clitocybe Fries (p. 322) Pileus more or less fleshy, margin at first incurved; stipe fleshy, often becoming hollow; gills decurrent. About ninety species. C. monadelpha Morg. = C. parasitica Wil. Growing in dense clusters; pileus 6-8 cm., convex or umbonate, 328 PLANT DISEASE FUNGI usually minutely scaly, mottled buff to yellow-):) rown in color; gills paler, becoming mottled, at first noticeably decurrent; stipe 10-16 cm. thick, solid, usually curved, darker than the pileus; black rhizomorphs present. It differs from Armillaria mellea in having no annulus, and in growing in denser clusters. i i c I'Ui. 309. — Clitocybe monadelpha, mycelium entering medullary ray. After Wilcox. The fungus causes a root-rot of apple very similar to that caused by Armillaria mellea. There are present typical subcortical strands, mostly between the cortex and cambium, and sometimes characteristic subterranean black rhizomorphs adhering close to the cortex of the roots. Fungous branches enter the wood chiefly through the medul- lary rays and there is later rapid vertical growth through the vessels and tracheids. The cell contents are destroyed, the hyphse often forming loops around the nucleus. The sporo- phores occur in groups at the base of the tree after the disease is well developed. Collybia Fries (p. 322) Pileus thin, fleshy, margin at first incurved; stipe cartilaginous. About two hundred seventy-five species. Fig. 310. PLANT DISEASE FUNGI 329 C. velutipes Curt. Cap 2-8 cm. wide, yellow-brown or reddish brown, rarely paler except toward the margin, smooth, very sticky when moist, con- vex to plane or somewhat recurved, often excentric or irregular through pressure. A common saprophyte which is reported by Stewart as the probable cause of death of the horse chestnut, also in linden. Mycena Fries (p. 322) Small, pileus usually bell- shaped, rarely umbilicate, membranous and more or less striate, at first with the straight margin applied to the stipe; gills only slightly toothed, not decurrent or only so by a tooth; stipe slender, cartilaginous, usually hollow. Fig. 311. A genus of some three hundred species. M. epipterygia Scop. Five to ten cm. high; pileus 1-2 cm. broad, viscid when moist, ovate to conic or campanulate, later more expanded, obtuse, the margin striate, sometimes minutely toothed, grayish, in age often reddish, stipe 2 mm. thick, flexuous or straight with soft hairs at the base; gills decurrent by a small tooth, varying in color from whitish through gray to a tinge of blue or red. Usually a saprophyte, but injurious to various kinds of trees. Widely distributed in the North temperate zone. Fig. 310. — Collybia velutipes. After Lloyd. 330 PLANT DISEASE FUNGI PLANT DISEASE FUNGI 331 FUNGI IMPERFECTI i- ^ (p. 56) In the preceding pages it has been repeatedly evident that one species of fungus may have two, even several different types of spores; in the Erysiphales the perithecial form and the conidial; in the Peronosporales oospores and conidia; in the Sphseriales the ascigerous form and several conidial forms; in the Basidiomycetes the basidial form and various conidial forms; in the Uredinales spring and summer stages and teKospores. Many of the lower or conidial forms are known while the higher spore forms, ascig- erous, basidial, or sexual form, are not known to be genetically connected with them, though it seems very probable, reasoning by analogy, that these conidial forms really constitute part of the life cycle of some fungus which embraces also a higher form of spore. It is probable, indeed certain, that some of these conidial forms at present possess also higher, as yet unknown, forms of fructification. It is likewise probable that in many cases the conidial form, though it does not now possess any higher spore form, did in its not re- mote phylogeny possess such forms; indeed that all of them are phylogenetically related to fungi which produced one of the higher types of spores. In some cases even in the absence of the higher spore it is possi- ble to refer the fungus to its proper order as, for example, is the case with the conidial forms of the Peronosporales, the summer or spring forms of the Uredinales, or the Oidium forms of the Erysi- phacese. Regarding many thousands of other conidial forms such refer- ence is impossible or hazardous, since from the conidial form the form of the higher spore can be inferred with only a small degree of accuracy or not at all. For example, the conidial form known as Glceosporium in the higher form of some of its species proves to be a Glomerella, in other cases a Pesudopeziza; some Fusariums prove to belong to the Hfe cycle of Nectria, others to that of Neocos- mospora, etc. In plant pathology and in systematic mycology it becomes necessary to classify, for convenience of reference and designation, ^ A new system for classification has recently; been proposed, v. Hohnel, System der Fungi imperfecti Fuckel. Mykologische Untersuchungen und Berichte 1 : Part 3, 301, 1923. 2 Diedicke, H. Uber die Systematik der Fungi imperfecti. Mitt. Thur. Bot. Ver. Weimar. 31: 71, 1914. 332 PLANT DISEASE FUNGI these multitudinous conidial forms of which the higher spore form is as yet unknown, which may exist now or which may have existed only in the more or less remote past. From analogy it is probable that most of them pertain to the Ascomycetes, though a few may find place among other classes. This whole group of forms, which is characterized chiefly by the imperfection of our knowledge of them, is classed together under the name Fungi Imperfecti. The Fungi Imperfecti are in a temporary way divided into orders, families, genera and species as are other fungi, with full recognition of the fact that future research will result, in many cases, in the disclosure of higher spore forms and the consequent removal of species to their proper place in the general scheme of classification. Recognizing the tentative nature of the genera in the Fungi Imperfecti these are spoken of as '' form-genera. " Pathologically, the Fungi Imperfecti are of high importance, often occurring on leaves, stems, fruit, wood, l^ark, etc., as active parasites, though very many are also saprophytes. Upon leaves they are particularly common causing diseased areas known as ''leaf spots." The Fungi Imperfecti display three principal types of fructifi- cation, pycnidia, acervuli and hyphae. Pycnidia are more or less spherical, hollow sporocarps on the inside of which conidia are borne on stalks, conidiophores, arising from the base or base and sides. Figs. 314, 325. The pycnidium may be of various colors though it is most commonly black or dark ; it may be superficial or imbedded, and with or without a beak, rostrum. The opening for the escape of the spores, ostiole, may be narrow or wanting, or it may be very large, round, irregular, etc. The walls vary from extremely delicate to very thick, smooth or variously provided with hairs, spines, etc. As need arises, it is common to speak of micro-pycnidia, and macro-pycnidia. Pycnidia with very small spores are sometimes called spermogonia, especially if the spores do not germinate, a cus- tom to be deprecated. The acervulus may be regarded as a pycnidium without its wall. It consists of a close bed of short conidiophores. Figs. 337, 339. Acervuli may be small or large, subepidermal, subcortical or super- ficial and may or may not be provided with hairs (setae) Fig. 337, of various kinds. An acervulus with a well marked basal stroma PLANT DISEASE FUNGI 333 is known as a sporodochium. Fig. 393. If the sporodochium stalk is markedly developed the structure becomes a coremiuin. It is sometimes quite difficult to distinguish between a pycnidium with an extremely large ostiole, or one with a very thin wall, and the acervulus. For such purposes thin longitudinal sections are most useful. Hyphae are conidiophores which grow for some distance above their supporting substratum and in more loose form than in the acervuli, so that the terminal parts at least stand out as separate threads, Figs. 346, 351, 361, 363. The hyphse may be simple and short, or long and much branched. When the hyphse are very short and closely crowded to form a sporogenous cushion the condition of an acervulus is ap- proached and confusion arises. The conidia borne in the pycnidia, acervuli or on the hyphse are of as various forms and types as is well conceivable and are made the chief basis for subdivision of orders into form-genera. They may be simple or compound, of almost any color, and may be borne in bisipetal succession in chains, or solitary, or in groups at the apices of the conidiophores. The following scheme of Saccardo presents the confessedly arti- ficial groups into which conidia may for convenience be divided. Scheme of Spore Sections Amerosporse: spores 1-ceIled, not stellate, spiral or filiform Hyalosporse: spores hyaline or clear, globose to oblong, continuous Phseosporge: spores dark, yellow to black, globose to oblong, continuous Didymosporse : spores, 2-celled Hyalodidymse : spores hyaline, 2-celled Phaeodidymse : spores dark, 2-ceIled Phragmosporse : spores 3 to many celled by cross septa Hyalophragmise : spores hyaline, 3 to many-celled Phaeophragmise : spores dark, 3 to many-celled Dictyosporse : spores septate, both crosswise and lengthwise, i. e., muri- form Hyalodictyse: spores hyaline, muriform Phseodictyse : spores dark, muriform Scolecosporse: spores needle-shaped to filiform, continuous or septate Helicosporse : spores spirally twisted, hyaline or dark, continuous or septate Staurosporse : spores stellate or radiate, hyaline or dark, continuous or septate 334 PLANT DISEASE FUNGI The mode of bearing spores and the color of the fungus both of which it is seen are made the basis of classification have been shown by Stevens and Hall and others to depend largely on en- vironment, while the septation of the spores, also a fundamental character in present classification, depends often on the age of the spores or on other factors. Many spores are unicellular until germination begins but then become typically 2-celled; e. g., Glceosporium. Such conditions have led to much inaccuracy in description and doubtless to undue multiplication of form-species. It has been quite customary, excusably so, to describe as new a form-species when no form-species previously described for the same host or its near botanical kin could be regarded as identical with it. Thus a Septoria found on Vitis would ordinarily be re- garded as new unless some of the Septorias already described on some of the Vitacese seemed to be the same, even though indis- tinguishable from dozens of Septorias on other families of plants. This course has led to enormous multiplication of so-called species in these form-genera giving rise to such form-genera as Septoria, Cercospora, Phoma and Phyllosticta with species numbering more than 1200, 700, 1600, 1200, respectively. Many of the form-genera are purely artificial — not at all well founded, e. g., Phoma is separated from Phyllosticta only by the supposed inability of the latter to grow on structures other than leaves, a distinction which has been shown to be quite untenable. It is evident that much careful study by cultures and cross in- oculations is needed to reveal the true status in these fungi. Since the conception of species is here most loose the form species given below must be regarded as purely tentative. The names are to serve merely as handles for convenience in treating of the va- rious parasites and in only comparatively few instances do they signify that they are really species. In many cases forms appearing under two or more names may prove eventually to be identical while in other cases forms may need to be subdivided. Key to Orders of Fungi Imperfect! Coiiidia produced in pycnidia 1. Sphaeropsidales, p. 335. Conidia not in pycnidia Hyphse innate within the matrix 2. Melanconiales, p. 364. Hyphse somewhat superficial, often floccose 3. Moniliales, p. 377. Conidia or other special reproductive cells unknown 4. Mycelia sterilia, p. 435. PLANT DISEASE FUNGI 335 The Sphaeropsidales (p. 334) Conidia in pycnidia which open by pores or shts, superficially resembling the perithecia of the Ascomycetes. The Sphaeropsidales are preeminently leaf-spotting fungi though many of them grow on fruit or stems causing blight, rot, cankers etc. The vast majority are saprophytes or parasitic on tissues of weak vitality, but not a few are active parasites. Key to Families of Sphaeropsidales Pycnidia globose, conic, or lenticular Pycnidia membranous, carbonous or coriaceous, black 1. SphaBrioidaceae, p. 335. Pycnidia more or less dimidiate, irreg- ular or shield-shaped, black 2. Leptostromataceae, p. 360. Pycnidia cup-shaped or patelliform, black 3. Excipulaceae, p. 363. The Sphaerioidaceae ^ Pycnidia globose, ovate, or clavate, leathery to carbonous, black or dark brown, opening by a pore, superficial, erumpent or covered ; stroma present or absent ; conidia variable in form, color, and division. The family is subdivided according to its spores as indicated on p. 333. Sphaerioidaceae-Hyalosporae Spores hyaline, 1-celled, spherical, elliptical or long. Key to Genera of SphaBrioidaceae-Hyalosporae Stroma none; pycnidia separate Pycnidia smooth; conidia borne singly, unappendaged Pycnidia free in the substratum; sub- iculum none Pycnidia not beaked Pycnidia opening by a regular pore, more or less sunken in the substratum Conidiophores simple or nearly so; pycnidia at first cov- ered, then erumpent Spores under 15 /z On leaves only 1. Phyllosticta, p. 336. ^ Diedicke, H. Sphseropsideae. Ann Myc. 9: 279, 1911. 336 PLANT DISEASE FUNGI Not on leaves 2. Phoma, p. 340. Spores over 15 /z 3. Macrophoma, p. 343. Conidiophores branched 4. Dendrophoma, p. 344. Pycnidia opening irregularly; spores blunt 5. Plenodomus, p. 344. Pycnidia beaked 6. Sphaeronema, p. 345. Pycnidia on a radiate subiculum. . . 7. Asteroma, p. 346. Pycnidia appendaged or hairy with long bristles, usually covering the entire pycnidium, conidia cylindric fusoid, usually curved 8. Vermicularia, p. 346. Pycnidia stromatic, superficial or sunken Pycnidia single on the stroma Pycnidia with a single chamber Conidiophores filiform; conidia of two kinds 9. Phomopsis, p. 342. Conidiophores indistinct or absent; stroma indistinct 5. Plenodomus, p. 344. Pycnidia several on each valsoid stroma scattered irregularly; conidia sepa- rate from each other Conidia straight, large, fusiform 10. Fusicoccum, p. 346. Conidia, ovate, or elongate P3^cnidia superficial or subsuper- ficial; conidiophores simple . 11. Dothiorella, p. 347. Conidia allantoid 12. Cytospora, p. 348. Phyllosticta Persoon^ -> ^ (p. 335) Pycnidia immersed, erumpent or with the beak piercing the epidermis, lenticular to globose, thin membranous, opening by a pore; conidia small, ovate to elongate, continuous, hyaline or green; conidiophore short or almost obsolete. On leaves. In part=Guignardia, Valsonectria, Mycosphserella. The genus is a very large one of over twelve hundred forms, few of which have been adequately studied. It differs from Phoma only in that it is foliicolous while Phoma is caulicolous, a distinc- tion which is not consistently maintained and which is untenable for generic limitation (see p. 334). The fungus produces leaf spots by killing or weakening the 1 Seaver, F. J. Phyllostictales. North American Flora. 6: pt. 1, 1922, 2 Ellis, J. B. and Everhart, B. M. The North American Phyllostictas. 1900. ^ Anderson, P. J. Index to American species of Phyllosticta. Mycol. II, 66, 1919. PLANT DISEASE FUNGI 337 leaf tissue with its mycelium. The spots are circular or subcircular, unless rendered angular by obstruction by veins, and the pycnidia may usually be seen with a lens in old spots unless the color of the leaf forbids. Similar effects follow on fruits. P. bellunensis Mart, on elm= Mycosphserella ulmi. P. brassicae (Curr.) West, on cabbage, etc. = Mycosph2erella brassicsecola. P. sphaeropsidea E. &. E. = P. paviae Desm. = Guignardia- aesculi, see p. 170. P. labruscae Thiim. on the grape =Guignardia bidwellii. See p. 166. P. tabifica Prill, is perhaps identical with Mycosphserella tabifica, See p. 175. P. maculiformis (Pers.) Sacc. on chestnut =Mycosphaerella maculiformis. P. solitaria E. & E. Pycnidia globose or sub-globose developing subepidermally; on the leaves 60-120 fi high, 60-110 ii wide, on the fruit and bark 60-95 fjL high x 107-166 ^t wide and usually with distinct ostioles which are rostrate on the fruit and leaves. Spores broadly eUiptic and coarsely guttulate, 7-11 x 6-8.5 /x. Pycnosclerotia produced Fig. 312. — P. solitaria. 1-month-old colony on apple agar. After Scott and Rorer. in the autumn, solitary or stromatic, large, 155-274 fx wide, 107- 238 fjL high with thick, dothideaceous membranes and without a definite ostiole; pycnosclerotia spores formed from the pseudo- parenchyma context and bearing a gelatinous cap or attenuated appendages at the broad pole. Conidiophores always present, distinct, columnar or filiform. Cells of the mycelium with large globules. 338 PLANT DISEASE FUNGI This fungus closely resembles Phoma uvicola B. & C, Phyllo- sticta pavise Desm., P. congesta Heald and Wolf and the imper- EPIDERMIS Fig. 313. — P. solitaria, section showing the dead tissue near the surface; the absciss layer and the modified tissue below it. After Guba. feet form of Guignardia vaccinii and the ascigerous form, as yet unknown, is probably a Guignardia. Fig. 314. — P. solitaria. 1, section through apple; 4, spores from apple blotch showing appendages; 6-7, germinating spores; 9, mycelium from corn-meal cultures. After Scott and Rorer. The cause of cankers on the twigs, petioles and pedicels; of leaf spots and of fruit blotches of apple. PLANT DISEASE FUNGI 339 P. limitata Pk. is reported on apple but probably is saprophytic. Spots round, minute, 2-6 mm., brown or reddish; pycnidia epiphyllous, black, few, punctiform; spores eUipsoid, 7-8 x 4 /z. P. pirina Sacc. Spots variable; pycnidia epiphyllous, punctiform, lenticular, 100-130 Mj context loosely cellular, brown; conidia ovoid to ellip- soid, 4-5 X 2-2.5 u. This was long regarded as the chief factor causing the common leaf spot on the apple and pear. Recent work throws doubt on this. P. congesta H. & W. Spot 0.5-0.8 mm., brown, vein-limited; pycnidia solitary, 50- 125 m; spores globose or slightly elongate, hyaline, 6-9 fj.. On plum leaves, fruit and twigs, causing blotch. P. circumscissa Cke. Amphigenous; spots orbicular, reddish-brown, at length de- ciduous; pycnidia scattered, minute; conidia elliptic, 8 x 2 )U. Spots and shot holes are formed on drupaceous hosts. P. prunicola Sacc. Spots subcircular, epiphyllous, sordid-brownish or ochraceous, margin subconcolorous; pycnidia scattered, punctiform; conidia ovoid to ellipsoid, 5 x 3 in. It is found on Prunus, causing leaf spots. Scurf is also produced on apple bark. P. betae Oud. Spots grayish-ochre, large and irregular; pycnidia epiphyllous, minute, densely clustered, brownish, subimmersed; conidia ellip- tic, 5-6 x 3 )U. The cause of leaf spots of beets. P. chenopodii Sacc. Spots irregular, scattered or confluent, ochraceous, fuscous margined; pycnidia lenticular, punctiform, 50 /x; conidia oblong- elliptic, 5x3 fx. A leaf spot is produced on spinach. P. apii Hals, forms brown spots on leaves of celery; pycnidia punctiform, black; conidia elliptic to ovate oblong. P. phaseolinaSacc. Spots irregularly scattered, subcircular, 2-10 mm., deep rusty brown, becoming lighter in center and darker margined; pycnidia scattered, 70-90 (jl; conidia ovoid oblong, 4-6 x 2-2.5 fi. It causes spotting of bean and cowpea. P. cucurbitacearum Sacc. Spots epiphyllous or amphigenous, sordid, whitish; pycnidia 340 PLANT DISEASE FUNGI punctiform, 80-100 n, lenticular; conidia oblong, 5-6 x 2]/) /x, curved. On muskmelon, cucumbers and other cucurbits, spotting the leaves. P. althaeina Sacc. Spots irregular, with a dark brown margin ; pycnidia few, lentic- ular, 90 11, ochraceous; conidia ovate-oblong, 6-7 x 3-4 ji. On hollyhock. P. caryae Rand. Spots large, irregular, often confluent, at first yellowish, then brown, sometimes becoming grayish in the center; perithecia 100 /z broad, punctate, epiphyllous; spores irregularly elliptical, 5x2//. On living leaves of hickory and the cause of nursery blight of Pecan. P. straminella Bres. is injurious on rhubarb. Other species are on peach, apple, pear, apricot, Ribes, straw- berry, cranberry, olive, hemp, hop, sweet potato, tobacco, alfalfa, rice, Hedera, rose, carnation, primrose, violet, hydrangea, lilac, cyclamen, digitalis, chrysanthemum, calla, vinca, antirrhinum, Pteris, narcissus, anthurium, dracaena, funkia, Laurus, elm, maple, horse chestnut, chestnut, box elder, catalpa, magnolia, ash, oak. Phoma (Fries) Desmaziere ^ ^ (p. 336) The genus as at present recorded contains over sixteen hundred forms. It is indistinguishable from Phyllosticta (see p. 336) ex- cept that it is caulivorous. Several species are regarded as conidial forms of Diaporthe, Mycosphserella, etc. P. reniformis on grape=Guignardia bidwellii. See p. 166. P. albicans Rob. & Desm. on chicory =Pleospora albicans. P. betae Fr. on beet=Mycosph2erella tabifica. See p. 175. P. bohemica Bub. & Kab. on fir tree needles=Rehmielliopsis. P. ambigua (Nitz.) Sacc. on pear= Diaporthe ambigua. P. sarmentella Sacc. on hop = Diaporthe sarmentella. P. pomi Pass. = Cylindrosporium pomi Brooks. Pycnidia papillate, 50-115 fx in diameter. Conidiophores short, conidia 2-3.5 x 0.8-1.0 ^t. It is reported as common on apples of almost all varieties, causing small, dry, sunken, brown fruit spots. 1 Hohnel, F. v. Uber die Gattung Phoma. Ann. Myc. 16: 98, 1918. ^ Shear, C. L. Phoma: A Sample of Mycological Nomenclature and Classifica- tion. Mycologia 15: 174, 1923. PLANT DISEASE FUNGI 341 P. lingam (Tode) Desm.^ =Phoma oleracea Sacc. Pycnidia scattered, globose-depressed, 100-400 /jl in diameter, subepidermal or superficial, often beaked; spores 3.5-5 x 1.5- 2.2 iJL, oblong. On cabbage and several other crucifers. The pycnidia are sparse on oval, sunken, diseased areas on the /eo^ Fig. 315. — P. lingam. A, showing pycnidia with spores streaming out; B, section; C, spores. After Manns. stems, and bacterial invasion follows soon in leaves, cambium, and xylem. In young infections the mycelium is intercellular; when old it penetrates the cells and causes collapse and drying. Infection may occur without wounding, pycnidia following in about two weeks. P. destructiva Plow., emend. Jamieson. Spots on tomato fruit, brown to black, membranous or car- bonaceous, definite; pycnidia most abundant toward the center of spot, subcutaneous, later erumpent, glabrous, brownish-black, subglobose, slightly papillate, not beaked, ostiolate, 30-350 /jl in diameter; conidiophores delicate, filiform, arising from inner cells; spores hyaline, continuous, 1-celled, 3-guttulate, subcylin- drical to subglobose, 2.8-8.5 x 1.7-3.4 /x; produced singly on un- branched filiform conidiophores. Parasitic on fruit of tomato, spots occurring on green and ripe fruit, usually near the stem end, 1-3 cm. in diameter. P. apiicola Kleb. Causes root rot of celery and occurs also on parsley, parsnip, carrot and caraway. P. piceina Pk. causes defoliation and death of spruce trees. ^ Henderson, M. P. The black-leg disease of cabbage caused by Phoma lingam (Tode) Desm. Phytop. 8: 379, 1918. 342 PLANT DISEASE FUNGI Other species are on peach, quince, Citrus, mulberry, grape, wheat and other grains, potato, bean, carrot, mangolds, cotton, sweet potato, hollyhock, lobelia, dahlia, cyclamen, fir, pine, Car- pinus. Phomopsis Saccardo ^ - (p. 336) As in Phoma, but with both filiform and oval spores. P. stewartii Pk. Pycnidia gregarious, commonly occupying grayish or brown spots, thin, subcutaneous, at length erumpent, depressed, minute, Y'?rY2 mm. broad, black; stylospores filiform, curved, flexuous or uncinate, hyaline, 16-25 x 1-1.5 ^i; spores oblong or subfusiform, hyaline, commonly binucleate, 8-12 x 2-3 yu; conidiophores slender, equal to or shorter than the spores. The fungus with its filiform spores only was noted as a parasite on Cosmos by Halsted. P. mail Roberts Pycnidia subglobose, scattered, aggregate or in a stroma, black, carbonaceous, plurilocular, ostiolate; spores subfusoid, contain- ing two oil drops, continuous, hyaline, 7-10 x 3-4 /z; conidiophores awl-shaped, 20 x 2.5 ix\ stylospores thread-like, hooked or S-shape, attenuate, 20-36 x 1.5 /z. On leaves and fruit of apple causing spots and on bark causing canker which results in death of the twig or branch. P. citri Fawcett Pycnidia scattered, ovoid, parencyhmatous, green or dark, 200-450 \x in diameter, erumpent, thick-walled, top easily broken away leaving spores exposed; ostiole 35-45 ix\ spores ovate or fusiform, often flattened on one side, hyaline, often 1-3 guttulate, 5-9 x 2.5-4 \i\ conidiophores 1.5 x 12-15 ix\ stylospores 20-30 x 0.75-1.5 IX, easily detached, often curved at one end. On dead branches and decayed fruit of Citrus causing rot. P. californica Fawcett Pycnidia mostly clustered, ovoid to conical, dark colored, 160- 300 ju in diameter, erumpent; ostiole 25-35 /i in diameter; spores ovate, mostly rounded at both ends, sometimes nearly acute at one end, hyaline, 7.7-9 x 3.4-4 \i\ conidiophores about 15 ju long; stylospores 22 x 0.3-1.6 ju, curved at one end. This fungus differs 1 Diedicke, H. Die Gattung Phomopsis. Ann. Myf. 9: 8, 1911. 2 Grove, W. B. The British species of Phomopsis. Kew Bull. Misc. Inf. 49, 1917. PLANT DISEASE FUXGI 343 distinctly from Phomopsis citri Fawcett in mode of growth, color, and principally by forming paraphyses instead of spores in culture. On dead outer bark and in decaying fruits of Citrus. P. vexans (Sacc. & Syd.) Harter.,= Phoma solani Hals., = Phoma vexans Sacc. & Syd., = Ascochyta hortorum (Speg.) CO. Sm. Pycnidia loosely gregarious; on fruit compact, at first buried, later erumpent, black without, beaked, flattened or irregular; on leaves and stems 60 to 200 fi broad, on fruit 120 to 350 n broad; spores subcylindrical, somewhat acute, 5-8 x 2.8 /x, continuous, hyaline, 2-guttulate, rarely 3 ; conidiophores simple, short, hyaline, continuous; stylospores filiform, curved, rarely straight, 13-28 M long. On leaf stem and fruit of egg-plant, causing stem blight, leaf spot, and fruit rot; also causing damping-off of seedlings. P. kalmiae Enlows causes a leaf blight of Kalmia. Macrophoma Berlese & Voglino (p. 336) As in Phoma, but the ostiole of the pycnidium not papillate and the pore smaller; conidia over 15 /z long; conidiophores sim- ple, short or filiform. M. tumefaciens Shear. ^ Pycnidia numerous, depressed, globose, buried in the cortex, subcarbonous slightly erumpent, subepidermal, 120-350 n in di- ameter; ostiole sUghtly elevated, non-papillate; pore small, dark- colored; pycnospores elongate, subellipsoid to subrhomboid, mostly obtuse, hyaline to pale lemon-yellow, 24-40 x 7.5-12 ju, ejected in coiled thread-like masses, contents granular; conidio- phores 6-12 fi long, simple, filamentous; hyphse dark brown, septate, 10-12 fx wide. On gall-like swellings of branches and twigs of Poplar. ^ Hubert, Ernest E. A new Macrophoma on galls of Populus trichocarpa. Phytop 5: 182, 1915. 344 PLANT DISEASE FUNGI M. fici Aim. & S. Cam. causes a canker on fig. The pycnidia vary from 150 to 300 // in diameter; the spores 14-26 x 9-11 m- Others are on olive, yew, fir, cassava, hydrangea, ivy, poplar. Dendrophoma Saccardo (p. 336);^ Pycnidia superficial or subepidermal and erumpent, carbonous, ostiole papillate; conidia elongate, conidiophores branched. A genus of some fifty species, chiefly saprophytes. D. obscurans (E. & E.) And.^ Spots large, 0.5-3 cm. or more, circular, oval, or sometimes fan-shaped, brown with broad purple zone; pycnidia scattered, amphigenous, flask-shaped, 150-300 n, erumpent; spores hyaline, continuous, bacillar or narrowly ellip- soidal, biguttulate, 5-7 x 1.5-2 n; conidiophores long, branched. On strawberry causing large leaf spots. D. marconii Cav. occurs on hemp stems; D. convallariae Cav. on leaves of Convallaria majalis; D. valsispora Penz. on living lemon leaves. Plenodomus Preuss ^ (p. 336) Pycnidia horny, immersed, opening irregularly; spores 1-celled, oblong, hyaline. P. destruens Harter ^ Pycnidia loosely gregarious, at first buried, later erumpent, largest diameter about 300 fx, beaked ; conidiophores simple, hyaline fragile, somewhat inconspicuous, 6-13 jj, long; conidia oblong, sometimes oval, with rounded ends, 7-10 x 3-4 /x, hyaline, con- tinuous, occasionally slightly curved, 2-guttulate; stylospores 6-15 fi long in the same pycnidium. On the stems of sweet potato. The organism attacks the cortex of the stem near the ground; also causes rot of the roots. P. fuscomaculans (Sacc.) Coons * Pycnidia 200-470 /x in diameter, globose, grouped, more or less immersed; spores oblong, 5 x 1 ^i, dilute olivaceous. The cause of a bark canker on apple. 1 Anderson, H. W. Dendrophoma leaf blight of strawberry. 111. Agr. Exp. Sta. Bui. 229. 1920. 2 Diedicke, H. Die Gattung Plenodomus Preuss, Ann. Myc. 9: 137, 1911. 3 Harter, L. L. The foot rot of sweet potato. Jour. Agr. Res. 1: 251, 1913. ^ Coons, G. H. Factors involved in the growth and the pycnidium formation of Plenodomus fuscomaculans. Jour. Agr. Res. 5: 713, 1916. PLANT DISEASE FUNGI 345 Sphagronema Fries (p. 336) Pycnidia superficial or not, pyriform, cylindric or globose, rostrum long; conidia ovate or elongate. Some seventy-five species, chiefly saprophytes, have been de- scribed. S. phacidioides Desm. on clover =Pseudopeziza trifolii. See p. 111. S. fimbriatum (E. & H.) Sacc. Pycnidia globose, 100-200 /z, surrounded by septate, hyaline hyphse; rostrum, 20-30 ^t long, apically fimbriate; conidia globose- elliptic, 5-9 n.^ The fungus grows in the sweet potato producing dark, almost black spots in the skin. The tissue below becomes olive-green. The dark mycelium is found penetrat- ing through and between cells of the diseased area where numerous oliva- ceous conidia are also present. The elongated beaks of the pycnidia rise like a small forest from the surface of the potato. In artificial culture the mycelium is ( dark, abundantly septate and with nu- /ji merous oil globules. Long multiseptate conidiophores with light colored tips i 2 6 arise from the medium. From these, hy- Fig 317.— s. fimbriatum; 1, pyc- ": mdium sending forth spores; 2, aline conidia are produced, apparently hyaline conidia; e, oiive conidia. , , -n. oirr r\^' After Halsted and Fairchild. endogenously. I^ig. 317. Olivaceous, globose to eUiptical, Fig. 317, conidia are formed within the me- dium on branches of the mycelium in much the same manner. The pycnidia develop in about nine days after inoculation and the conidia are extruded from the fimbriate mouth of the long rostrum. Inoculations proved the pathogenicity of the organism, typical black rot appearing in about three weeks after infection. Other species are on sugar-cane, cranberry, Prunus, rice. 1 Recently Elliott indicated that the spores described as pycnidiospores are really ascospores. (.Phytop. 13: 56, 1923). r 346 PLANT DISEASE FUNGI Asteroma De Candolle ^ (p. 336) Pycnidia very small, globose, erumpent, often on a mass of hyphse; conidia ovate or short cylindric. In part = Gnomonia. See p. 196. A. padi (DC.) Grev. on Prunus=Gnomonia padicola. Vermicularia Fries (p. 336) Pycnidia superficial, or erumpent, globose depressed to globose clavate, leathery or carbonous, black, ostiolate or not, beset with rather long, stiff, septate, dark colored bristles; conidia cylindric- fusoid, often curved. V. dematium (Pers.) Fr. Pycnidia erumpent, superficial, 80-120 n, conic, then depressed, often confluent, black, spines pale at the ends, 150-200 x 5 m> conidia cylindric-elongate, 20 x 4-6 ju, apically rounded, curved. Commonly a saprophyte, this fungus occasionally causes aspar- agus disease. On ginseng it pro- duces a stem anthracnose. Other species are on blue grass, ivy, camellia, carnation, Sedum, Dracaena, rhubarb. \{Z\U Fig. 318.— V. dematium. C, a nearly ma- ture "perithecium"; S, spores; R. hyphae. After Reed. Fusicoccum Corda (p. 336) Stroma subepidermal, several-chambered, erumpent, leathery, black; conidia fusoid, straight and usually large. Some forty species, several of which are regarded as conidial forms of Diaporthe and Gnomonia. F. veronense Massal on Sycamore and Oak = Gnomonia veneta. See p. 196. F. viticolum Red. on grape = Cryptosporella viticola. See p. 203. F. putrefaciens Sh. is on cranberry. ^ Diedicke, H. Die Gattung Asteroma. Ann. Myc. 9: 534, 1911. PLANT DISEASE FUNGI 347 Fig. 319. — F. viticolum, compound pycnidium, germinating spores, paraphyses. After Reddick. Dothiorella Saccardo (p. 336) Pycnidia erumpent, on a stroma, leathery, ostiole papillate or not; conidia ovate or elongate. D. ribis (Fcl.) Sacc, on a wide range of hosts = Diaporthe strumelia. Fig. 320. — D. mori. N, section of stroma, O, conidiophores and conidia. After Allescher. D. gregaria Sacc. Pycnidia erumpent, 180-260 fx in diameter; spores oblong- fusoid, hyaline, continuous, spindle-shaped, 18-29 x 5-7 m; conid- iophores 10-15 X 3-4 fjL. The cause of Melaxuma on walnut, in which disease large, black, sunken cankers are produced on limbs and trunk, often accompanied by sudden wilting. D. quercina (C. & Ell.) Sacc. causes a twig blight of oak. 348 PLANT DISEASE FUNGI Cytospora Elirenberg (p. 336) Stroma superficial or erumpent, tubercular, with irregular chambers; conidia elongate allantoid. Ascigerous forms belonging to Valsa are known. C. chrysosperma (Pers.) Fr.^ Stromata subcuticular; spores hya- line, allantoid, continuous, 4 x 1 /i, is- suing in cirri. Fig. 321. -Cytospora. Section ^^ P^P^^^ ^ud willoW, chcstnut, through a stroma. After Ches- maple, mulbcrry, hibiscus, causing can- ker in trunk, limb and twig. After the mycelium has grown for weeks in the bark the pyc- nidia are formed in large numbers. Sphaerioidaceae-Phaeosporae - Conidia 1-celled, dark, globose, ovoid or oblong. Key to Genera of Sphaerioidaceae-Phaeosporae Conidia large, ovate to elliptic 1. Sphaeropsis, p. 348. Conidia very small, globose to ellipsoid .... 2. Coniothyrium, p. 349. Sphaeropsis Leveille Pycnidia immersed, erumpent, globoid, black, leathery, mem- branous, with the ostiole papillate; conidia ovate or elongate; conidiophores rod-like, typically 1-celled, dark. About two hundred species, several of them important plant pathogens. S. malorum Pk. =Physalospora cydonise Arn. See p. 179. S. tumefaciens Hedges Perithecia subglobose, papillate, black, ostiolate, erumpent, 152-224 X 120-192 /x; spores oblong or ovoid, continuous or rarely 1-septate, hyaline to pale yellow, 16-32 x 6-12 fx. The fungus causes tumors, from a few millimeters to 6 cm. in diameter, on lime and orange. These often bear witches' brooms. ^ Long, W. H. An undescribed canker of poplars and willows caused by Cytospora chrysosperma. Jour. Agr. Res. 13: 331, 1918. - Diedicke, H. Die braunsporigen spharopsideen. Ann. Myc. 11: 44, 1913. PLANT DISEASE FUNGI ^49 Coniothyrium Corda (p. 348) Pycnidia subcortical, erumpent or not, globose or depressed, ostiole papillate, black, leathery to carbonous; spores small, ellip- soid, conidiophore reduced or absent. More than one hundred fifty species. C. pirinum (Sacc.) Shel. is common on apple leaf spots but is not regarded as their cause. C. tumefaciens Gus. is described as the cause of a rose canker. C. fuckelii Sacc. on apple = Leptosphaeria coniothyrium. See p. 185. C. diplodiella (Speg.) Sacc. Pycnidia minute, subcuticular, erumpent, brown, 100-150 yu; conidia ovoid to elliptic, 7-11 x 5.5 n; conidiophores simple or branched, hyaline, filiform. This is the cause of a white rot of grapes. c-^ I <«i *-v,^ a r>/ I" — ^^-=- --/. Fig. 322. — C. diplodiella, section through pycnidium. After Scribner. An ascigerous connection with Charrina has been reported in France. The mycelium is abundant in the affected pulp and sometimes upon the seeds. Peduncles are often killed. The pycnidia are subcuticular, first pink, then white, later brown. C. caryogenum Rand Mycelium brown, sometimes almost hyaline where not sub- merged; pycnidia roundish, ostiolate, thin-walled, dark brown, about 200 X 250 fj. in diameter; sporophores short and indistinct; spores pale brownish, elliptical, 1-celled, 2.5-3.6 x 1.8-2 jjl. Upon pecan kernels causing dark-brown, irregularly roundish. 350 PLANT DISEASE FUNGI surface spots with a hemisphere of pithy tissue beneath, which is surrounded by a brownish layer of host cells. Others are on mulberry, elm, vinca. Sphaerioidaceae-HyalodidymaB Conidia hyaline, 1-septate, ovoid, ellipsoid or oblong. Key to Genera of Sphaerioidaceae-Hyalodidymae Pycnidia separate, not beaked Pycnidia in discolored areas, maculicole Pycnidia immersed, then erumpent, per- forate; conidia muticaie 1. Ascochyta, p. 350. Pycnidia not maculicole, smooth, conidia muticate; conidiophores 1-spored: Pycnidia without subicle 2. Diplodina, p. 351. Ascochyta Libert ^ Usually producing definite spots; pycnidia globose-lenticular, ostiolate; conidia ovate. About two hundred fifty species. A. gossypii Syd.- Spots amphigenous, roundish or irregular, 3-10 mm. in diameter, dingy ochra- ceous, bordered with dark fuscous; pycnidia am- phigenous, lens-shaped to globose, 80-100 n in di- ameter, ochraceous brown, pierced by a round pore 20-25 ijl in diameter; spores oblong or sharply cylindrical, rounded at both ends, 1-septate at or about the middle, not at all or barely constricted, hyaline, 8-10 x 2-4 n; sporophores not seen. On cotton leaves, stems, bolls, causing serious injury. Fio. :323.-A. oitri. A. ablemoschi Harter ' spores. After gpots somcwhat circular, often with a brown to black margin, more or less zonate; pycnidia often crowded, brown to black, pyriform to globose, at first buried, becoming erumpent, 65-225 /x in diameter, ostiole small; spores cylindrical to oval, 4-14 x 2-4 /x, hyaline, 1-celled for a long time, finally 1-septate. The cause of a pod spot of okra. ^ Davis, J. J. North American Ascochytse. Trans. Wis. Acad. Sci. 19: 655, 1919. 2 Elliott, John. A. A new Ascochyta disease of cotton. Ark. Agr. Exp. Sta. Bui. 178, 1922. ^ Harter, L. L. A hitherto unreported disease of okra. Jour. Agr. Res. 14: 207, 1918. PLANT DISEASE FUNGI 351 A. piniperda Lindau ( = Septoria parasitica) is parasitic on fir and spruce causing leaf blight, especially of seedlings. Pycnidia imbedded in the stem tissue, 85 ix in diameter; spores 2-celled, ellipsoid, hyaline, 9 x 1.5 /x. A. fragariae Sacc. Pycnidia partly immersed, black, 100-125 m; conidia fusiform to cylindric, constricted, 14-27 x 4-5.5 /z. This was reported as occurring in injurious form on strawberry leaves, causing spots, at first red, later brown. A. chrysanthemi Stev. Pycnidia few, immersed, early erumpent, single or scattered, hemispheric, amber-colored, 100-200 m; ostiole central, small, often raised by a neck, dark-bordered; conidia oblong, straight or irregular, 3-6.2 x 10-20 M; apically obtuse, septum often ob- scure, sometimes more than one; not constricted till germination. It causes blighting of ray flowers of chrysanthemums. A. medicaginis Bres. Spots small, angular, pale, clustered; pycnidia sublenticular, apiculate, pale, becoming black, 200 x 160 m, context parenchy- matous; conidia oblong, obtuse, scarcely constricted, 10-12 x 4- 4.5 IX. The cause of spots on alfalfa. A. lycopersici Brum. Spots red or brown, large, rounded or irregular; pycnidia sparse, minute, black; conidia oblong, constricted, 8-10 x 2.5 /x. Spots are produced on leaves and fruits of egg plant. Others are on grape, horse-radish, cherry, strawberry, cabbage, beet, lettuce, rhubarb, okra, vetch, tobacco, Melilotus, Polemo- nium, columbine, pinks, clematis, violet, digitalis, iris, primrose, horse chestnut, maple, poplar, Juglans, ash, spruce, butternut, oak, walnut, and various grasses and grains. Diplodina Westendorp (p. 350) Pycnidia immersed or erum- pent, globose; ostiole papil- late, black, small; spores elon- gate. It differs from Diplodia only in the hyaline spores. D. citrullina on cucurbs= Mycosphserella citrullina. See p. 174. Other species are on spruce and willow. Fig. 324. — D. castaneae, pycnidium and spores. After Delacroix. 352 PLANT DISEASE FUNGI Sphaerioidaceae-Phaeodidymae Conidia dark, I-septate, ovoid to oblong. Key to Sphaerioidaceae-Phaeodidymae Pycnidia separate, erumpent, not beaked, smooth; conidia without a mucous layer, muticate, 15 m or more long . . Pycnidia on a subicle enclosed in a hem- ispheric stroma 1. Dipiodia, p. 352. 2. Lasiodiplodia, p. 353. Dipiodia Fries Pycnidia immersed, erumpent, carbonous, black, usually os- tiolate-papillate; conidia ellipsoid or ovate; conidiophores needle- shaped, simple, hyaline. Over four hundred fifty species, many of them saprophytes. D. zese (Schw.) Lev. On ears and stalks of corn, pycnidia borne on the husks, cobs, stalks and rarely the grains, gregarious, small, lenticular to flask- shaped or irregular, papil- late; conidia elliptic, straight or curved, con- stricted or not, 25-30 x 6 ju. It occurs as the cause of a very serious dry rot of ear corn. The growing mycelium is hyaline and much branched. Pycnidia in the cob are principally on the scales which surround the inner ends of the kernels and are set in a dense mass of white mycelium. On dead stalks the pycnidia form below the rind, particularly at the nodes, breaking through during the following summer and extruding the spores in cirri. Spores placed under the husk or in the silk, or sprayed upon plants in suspensions, result in disease. It is also reported that infection is often by way of the root system, the mycelium reaching the grains through the stem and from the cob. Fig. 325. — Pycnidia of Dipiodia, from corn kernel. After Burrill and Barrett. PLANT DISEASE FUNGI 353 D. gossypina Cke. causes a rot of the cotton boll and stem. D. macrospora Earle Pycnidia scattered, large, erumpent, carbonous; conidia elon- gate, irregularly clavate, curved or constricted, 70-80 x 6-8 fx. This is responsible for a corn mold similar to that mentioned above. D. longispora C. & Ell. causes twig blight of oak and chestnut. D. natalensis Evans, or a species very near it, is reported as the cause of gummosis of peach and orange in Florida. Pycnidia scattered, covered, later erumpent, black; papillate, 150-180 m; spores eUiptical, 1-septate, not constricted, dark, 24 X 15 )U, exospore with striated bands. Other parasitic species are on cherries, oranges, avocado, rice, coffee, mulberry, poplar, pine, conifers. Lasiodiplodia EUis & Everhart i (p. 352) Pycnidia collected on a stroma, covered with a brown mycelium, paraphyses among the conidiophores. Otherwise as in Diplodia. L. tubericola E. & E. Pycnidia globose, 250-305 yu; stro- matic mass about 1 mm. in diameter; conidia elliptic, 18-22 x 11-14 )u, not constricted; conidiophores short; pa- raphyses 45-55 IX long, overtopping the conidia. On sweet potato. L. triflorae Higgins Pycnidia embedded in the cortex, sub- epidermal or sometimes on the surface of the bark, scattered or aggregated; ostiole not papillate; walls more or less thickened and stromatic, naked or vari- ously covered with hairs; spores oblong, 22-25 X 13-16 ju, at first hyaline and continuous, but becoming dark brown and 2-celled after extrusion from the pycnidia, in- termixed with paraphyses. On trunk and branches of various species of Prunus infecting principally the conducting tissue and the medullary rays of the wood and causing gummosis, followed by wilt and death. En- trance is gained through wounds. 1 Fetch, B. A. On Lasiodiplodia. Roy. Bot. Gard. Paradeniya. 4: 445, 1910. FiQ. 326. — Lasiodiplodia tuberi- cola. Pycnidium, paraphyses and spores. After Clendenin. 354 PLANT DISEASE FUNGI Sphaerioidac eae-Hyalophragmiae Conidia hyaline, 2 to many-septate, oblong to fusoid. Stagonospora Saccardo Pycnidia superficial or erumpent, no subicle, globose, ostiolate, papil- late, black, membranous or subcar- bonous; conidia elongate 3 or more- celled, muticate. Over one hundred species, chiefly saprophytes; differing from Hender- sonia only in the hyaline conidia. S. carpathica Bauml. . Spots circular, 1-3 mm., light brown with a narrow, darker border; Fio. 327.— stagonospora. C. pycnidium pycnidia 120-180 U', COnidia CSCap- in section. D, spores. After Corcla. .. . ' ,-ii mg m a gelatmous mass, straight or slightly curved, 14-28 x 4 /x, 2 to 5-celled, frequently slightly constricted. It causes leaf spots on alfalfa. S. iridis Mass. occurs on iris. Sphaerioidaceae-Phaeophragmiae Conidia hyaline, 2 to several-septate, oblong to fusoid. Hendersonia Berkley Pycnidia separate, immersed, erumpent or not, globose with a papillate ostiole or depressed, membranous or subcarbonous; no subicle; conidia muticate, elongate or fusoid, 2 to many-septate. Some two hundred fifty species, chiefly sap- rophytic, although there are several parasitic species. H. mali Thiim. Epiphyllous; pycnidia disciform, large, scattered, black, on brownish, orbicular, violet-margined spots; conidia clavate, apex rounded, base some- what acute, not constricted, 12-14 x 4-5 /x. On leaves of apple. H. foliicola (Berk.) Fcl. Pycnidia epiphyllous, brownish-black, subglobose, subelliptic Fig. 328.— Hender- sonia, iiymenium and spores. Af- ter Starback. PLANT DISEASE FUNGI 355 or irregular; conidia elliptic to clavate, obtuse, 3 to 5-septate; conidiophores filiform, radiating. On Juniperus and Pine. Others are on quince, rice, coffee. Sphaerioidaceae-Scolecosporae Conidia hyaline or light colored, elongate-fusoid, rod-shaped or filiform, continuous or septate. Key to Genera of SphaerioidaceaB-ScolescoporaB Pycnidia separate, membranous or carbonous, immersed or erumpent, smooth, not beaked Pycnidia maculicole, mainly phyllogenous ; conidia hyaline 1. Septoria, p. 355. Pycnidia not maculicole Pycnidia complete at top, usually papil- late 2. Rhabdospora, p. 359. Pycnidia more or less incomplete at top, not exposing a gelatinous mass of spores, foliicole 3. Phleospora, p. 359. Septoria Fries h 2, 3 Pycnidia immersed, usually on leaf spots, globose lenticular, ostiolate, membranous, black; conidia narrowly elongate to fili- form, multiseptate, hyaline, conidiophores very short. Over twelve hundred species, all parasitic, several of them of considerable economic importance but most of them occurring on non-economic hosts. In part=Mycosph8erella, Leptosphseria. The genus is a very large one similar to Phoma and Phyllosticta except in its spore form, and in the ostiole which is frequently very large. Septoria and Phelospora are distinguished only by the lesser development of the walls of the latter and many species which in early stages pass as Phleospora would in older stages be classed as Septoria. Septoria and Rhabdospora are distinguished only by the part 1 Diedicke, H. Die Gattung Septoria. Ann. Myc. 10: 478, 1912. 2 Garman, Philip and Stevens, F. L. The Genus Septoria presented in tabulation with discussion. Trans. 111. Acad. Sc. 13: 176, 1920. ^ Beach, W. S. Biologic specialization in the genus Septoria. Amer. Jour. Bot. 6: 1, 1919. 356 PLANT DISEASE FUNGI of the host affected, stem or leaf, and many forms in these two genera are undoubtedly identical. S. avenae Fr. = Leptosphseria avenaria. See p. 185. S. rubi=Mycosph2erella rubi. See p. 173. S. piricola Desm. on pear and apple = My cosphaerella sentina. See p. 173. S. populi Desm. on Populus=Mycosph8erella populi. S. phlogis Sacc. & Speg., on Phlox =Leptosph8eria phlogis. S. ribis Desm. Hypophyllous; spots small, irregular, bounded by the leaf veins, brownish-purple; pycnidia innate, minute, convex, brownish-black; cirri reddish in mass; conidia elongate, linear, curved, 50 fi long. On gooseberry and currant, causing leaf spots and defoli- ation. S. aciculosa E. & E. Pycnidia innate to superficial, grouped, minute, amphigenous; conidia needle-shaped, contin- uous, 15-20 X 0.75 /i. Fig. 329. — S. ribis, a pycnidium and spores. After Longyear. It is found on the strawberry. S. fragariae Desm. Epiphyllous; spots suborbicular, brown, with reddish-brown margin; pycnidia minute, innate, prominent, brownish; cirri white; conidia cylindric, obtuse, 3-septate. Perhaps =Mycosphaerella fragariae. Seep. 171. On strawberry, cultivated and wild, forming circular leaf spots. S. bataticola Taub. Pycnidia imbedded under the epidermis, with open mouths protruding or free, varying from 70-130 jjl, readily falling out; spores hyaline, vermiform, curved to straight, varying from 15- 80 X V3~S^2 M- Parasitic on living leaves of sweet potato. S. pruni Ellis Spots dark brown, dry, subrotund, soon breaking out, 1-3 mm.; pycnidia brown, immersed, 60 /z; conidia linear, obtuse, 4 to 6- septate, 30-50 x2 /jl. On plum. S. graminum Desm. Spots slightly elongate, pale, fuscous-margined, limited l)y the PLANT DISEASE FUNGI 357 leaf veins; pycnidia seriate or scattered, brownish; conidia very slender, straight or curved, non-septate, multiguttulate, 55-75 x 1-1.3 IX. This is a frequent saprophyte or weak parasite on wheat, oats and numerous wild grasses. Under some conditions it becomes an injurious parasite, especially upon winter wheat. S. betae West. Spots pale brown, white in the center, brownish-margined; pycnidia epiphyllous, minute, black, prominent; conidia cylindric, straight or curved, white in mass. It was noted causing a beet leaf spot. S. citrulli E. &. E. Spots small, round, white, scattered; pycnidia mostly solitary, one in the center of each spot, but slightly prominent; conidia cylindric or clavate-cylindric, 10-25 x 1.5-2 ^. On watermelon leaves. S. cucurbitacearum Sacc. is also on cucurbits. S. petroselini Desm. Spots brown, in age white, amphigenous; pycnidia epiphyllous, minute, olivaceous, prominent; conidia filiform, straight or curved, 35-40 X 1-2 /i. On parsley. S. apii Chester is very destructive on celery. The pycnidia are abundant in the leaf spots and in the case of stored celery they are found scattered over the blanched petioles. S. lycopersici Speg. Spots large, often confluent and covering the entire leaf, sordid cinereous, subindeter- minate; pycnidia scattered, hypophjdlous, lenticular- liPTYiicrkViAvin r»rr»-mi-nckn+ Fig. 330. — S. apii, pycnidium showing spores ooz- lieinifepiieilO, p 1 U 111 men l, -^^^ through the ostiole. After Jensen. membranous; conidia elon- gate, cylindric, 70-110 x 3.3 ^, pluriseptate. The cause of leaf spots of tomato. S. lactucae Pass. Spots irregular, brownish, angulate, sometimes destroying the 358 PLANT DISEASE FUNGI entire leaf; pycnidia minute, punctiform, scattered, 90 n in diam- eter; conidia filiform, straight or curved, 25-30 x 1.7-2 fx. On lettuce. S. consimilis E. & M. Distinguishable from the preceding by the more indefinite spots, slightly larger pycnidia, 90-100 fx, and longer conidia, 30-45 x 2-2.5 fjL. It causes brown spots on lettuce leaves. S. spadicea P. & C. causes a common twig blight of pine. Pycnidia not spot-forming, becoming slightly erumpent on inner surface of browning needles, scattered, membranous, fuscous- olivaceous, subimmersed, 190-225 fx in diameter. Spores hyaline, cylindrical, slightly curved or flexuous, apex acute, 1-septate, rarely constricted at septum, 3-4 x 30-45 fx. Conidiophores short. S. secalis P. & D.^ is on rye. Pycnidia subepidermal, black, globose to subglobose, smooth, 85-130 /x in diameter; spores hya- line, 3-septate, usually curved and rounded at the ends, 2-3 . 5 x 25-49 M. S. passerinii Sacc. is on barley. Spores 1.7-3 x 23-46 fx, averag- ing 2.3 X 34 ju; pycnidia subepidermal, black, smooth, globose to subglobose, 80-150 fx in diameter; ostiole oval to elliptical, smooth, substomatal. S. agropyri E. & E. is on Agropyron repens; S. bromi Sacc. on Bromus inermis. ^^ 011:5 "" f\<^^133> X \ ^=^=Ci^ =>> ,^-^ ^ ^ ^ Fig. 331. — Sporo.s of S. nodorum. After Weber. S. nodorum Berk.^- ^ causes spotting of the glumes, glume blotch, and rachis of wheat. 1 Weber, George F. Septoria disease of rye, barley, and certain grasses. Phytop. 13: 1, 1923. ~ Rosen, H. R. Septoria glume blotch of wheat. Ark. Agr. Exp. Sta. Bui. 175. 1921. ^ Weber, George F. Septoria diseases of wheat. Phytop. 12: 537, 1922. PLANT DISEASE FUNGI 359 Pycnidia spherical, flattened or elongate, subepidermal, 160- 210 ju in diameter; wall thin, soft, light brown, becoming dark brown or black; ostiole circular to oval, opening between the guard cells of the stomata; spores oblong, cylindrical, straight, curved or angularly bent, obtuse and rounded at the ends, hyaline, 3-septate, guttulate, 2-4 x 18-32 /i. S. tritici Desm.^ Pycnidia subepidermal, in substomatal chambers, globose to sub- globose, in rows parallel to the vascular strands, brown to black, wall smooth, pseudo-parenchymatous, 1-3 cells thick, 80-150 /x in dia- meter; ostiole circular to oval, slightly raised, 12-20 fx in diameter; spores slender, cylindrical, hyaline, 3 to 7-septate, ends rounded, contents homogeneous or slightly guttulate, 1.75-2.7 x 39-70 /x. On wheat causing speckled leaf blotch and kilHng many seedlings and tillers. S. gladioli Pass. Pycnidia 100-160 fj, in diameter; conidia 3-septate, 20-55 x 2-4 fi, cylindrical, straight, hyaline. On gladiolus causing disease on leaves and corms. Other species are on cherry, plum. Citrus, grape, cranberry, rice, hemp, tobacco, cowpea, alfalfa, sweet potato, horse-radish, snapdragon, rose, hydrangea, iris, cyclamen, Sedum, Hedera, carnation, chrysanthemum, Kalmia, Azalea, phlox, narcissus, veronicas, hollyhock, sunflower, lily-of the-valley, oleander, chest- nut, walnut, horse chestnut, sycamore, maple, ash, redbud, linden, Robinia, Spirea, dogwood, poplar, pecan. Rhabdospora Montaigne (p. 355) Pycnidia innate, erumpent, globose or depressed, brown or black; conidia as in Septoria. Similar to Septoria, but on stems. R. rubi Ellis. Pycnidia black, subglobose, innate, erumpent, scattered, 100-195 (jl; conidia linear, curved, 3 to 4-septate, 40- 45 X 3 /x. On Rubus. R. oxycocci Sh. is on cranberry. Phleospora Wallroth (p. 355) Pycnidia innate, imperfectly developed and chiefly formed of modified host tissue; conidia elongate-fusoid, thick, 2 to many- septate. 1 Weber, George F. Septoria diseases of wheat. Phytop. 12: 537, 1922. 360 PLANT DISEASE FUNGI This genus closely approaches the Melanconiales in structure. Several forms have been shown to be allied to Mycosphaerella. P. mori (Lev.) Sacc. on Morus=Cylindrosporium mori= My- cosphaerella. Several species occur as parasites on elm, mulberry, maple, sycamore, hawthorn. Leptostromataceae ^ (p. 335) Pycnidia membranous or carbonous, black, more or less dis- tinctly dimidiate, scutiform, astomous, ostiolate or cleft, erumpent or superficial. Over two hundred species. Lep tos tr omatac eae-Hy alospor ae Conidia hyaline, 1-celled, globose to ovoid. Key to Genera of Leptostromataceae-Hyalosporae Pycnidia separate Pycnidia not cleft Conidiophores short or lacking, pycnidia without subicle; conidia muticate Pycnidia gelatinous within 1. Gloeodes, p. 360. Pycnidia not gelatinous within, not stellate 2. Leptothyrium, p. 361. Pycnidia more or less clearly cleft length- wise, elongate or lanceolate 3. Leptostroma, p. 362. Pycnidia in a stroma, phyllogenous 4. Melasmia, p. 362. Gloeodes Colby Mycelium strictly superficial, dark colored, septate, profusely branched, often anastomosing, constituting a thallus, often fern- like in appearance but occasionally of other types; pycnidia dim- idiate, membrano-carbonous, interior gelatinous; paraphyses present; conidia oblong, one-celled, hyaline. G. pomigena (Schw.) Colby ^ Pycnidia dark brown, dimidiate, scattered or aggregated, super- ficial, rupturing irregularly; conidia oblong, sometimes slightly curved, one-celled, hyaline, 10-20 x 4-7 /x; conidiophores short or lacking; paraphyses septate, gelatinous, slender, blunt, longer than the conidia. ^ Diedicke, H. Die Leptostromaceen. Ann. Myc. 11: 172, 1913. 2 Stevens. F. L. Bui. 10, Bishop Museum. 1925. PLANT DISEASE FUNGI 361 On fruits and stems of certain species of Pyrus causing sooty blotch. The conidial stage is rare. ^nsr*^ Fig. 332.— Sooty blotch thalli of fern-like type. After Colby. Leptothyrium Kunze & Schweinitz (p. 360) Pycnidia superficial or erumpent, dimidiate, scutiform, mem- brano-carbonous, black, coalescing or scattered, ostiole variable, structure cellular; conidia ovoid-oblong to fusoid. Some one hundred species. In part=Gnomonia and Gnomoniella. L. alneum (Lev.) Sacc. on alder= Gnomoniella tubiformis. 362 PLANT DISEASE FUNGI L. pomi (M. & F.) Sacc. The fungus usually reported under this name forms minute, sterile, superficial, black spots, the so-called fly-specks, on apple. This fungus probably is an im- perfect stage of one of the Hemi- sphffiriales. See p. 145. ooD^g^^s£3ii-_ ^- oxycocci Sh. "^^S^.S^^?^ Pycnidia black, dimidiate, Fig. 334. — Leptothy- amphigcnous, Scattered, sub- num oxycocci. Sec- . . Fig. 333. — Lepto- tion of a pycnidium, COriaCCOUS tO COriaCCOUS, irregU- thvrium oxycocci. showing its dimidi- , , i i i i • i i Four spores. Af- ate character. Af- larly SUbglobOSC, Subepidermal, ter Shear. ter Shear. erumpent, ruptuHng irregularly; conidia subfusoid, sometimes slightly curved, pseudoseptate, 10- 15 X 2.5-3 fi; conidiophores simple, straight, tapering, slightly longer than the conidia. On cranberry. Others are on honeysuckle, maple, box, strawberry, pears, Cereus. Leptostroma Fries (p. 360) Pycnidia dimidiate, subsuperficial, applanate, elongate, black, more or less hysterioid; conidia ovate, elongate or allantoid. In part=Hysteriace8e. There are some sixty species. L. larcinum Fcl. on larch = My cosphaerella larcina. L. piricola B. & S. occurs on the pear. L. punctiforme Wallr. is on willow. Melasmia Levielle (p. 360) Pycnidia dimidiate, carbonous, black, often on an effused, black stroma; conidia allantoid. In part=Rhytisma. Over twenty species. M. acerina Lev. is the conidial form of Rhytisma acerinum. See p. 120; M. punctata S. & R. and M. salicina Lev. of the two corresponding Rhytismas. See p. 120. Leptostromataceae-Hyalophragmiae Conidia oblong to fusoid, hyaline, 2 to several-septate. PLANT DISEASE FUNGI 363 Entomosporium Levielle Pycnidia depressed, subglobose, not ostiolate, black; conidia 4-celled, cruciate, each arm 1-ciliate. A genus of three species of parasites. In part= Fabraea. E. mespili (DC.) Sacc. = F. mespili. E. maculatum Lev. on pear and quince = F. maculata. See p. 112. E. thumenii (Cke.) Sacc. occurs on hawthorn. Excipulaceae (p. 335) Pycnidia membranous to carbonous, black, cup-shaped, patel- late or hysterioid, at first more or less spherical but at length widely open, erumpent or superficial, glabrous or hairy. Excipulaceae-Hyalosporae Conidia hyaline, continuous, globose to oblong. Key to Genera of Excipulaceae-Hyalosporae Pycnidia pilose or setose, cupulate; conidia muticate 1. Amerosporium, p. 363. Pycnidia smooth or nearly so Pycnidia more or less cup-shaped or dis- ciform, black, of cellular context, subglobose, irregularly dehiscent and collabent 2. Dothichiza, p. 364. Pycnidia valvately gaping; conidiophores typically branched 3. Sporonema, p. 364. Amerosporium Spegazzini Pycnidia subcupulate, setulose, conidia cylindric to ellipsoid. Some twenty-five species, chiefly saprophytes. A. ceconomicum E. & T. Spots orbicular, 2-6 mm., white above with a reddish border, mostly entirely reddish below; pycnidia epiphyllous, erumpent, conic-hemispheric, broadly perforate above, beset with straight, spreading, grayish-black, septate bristles, 100-150 x 4 /-t; conidia oblong-fusoid, 18-27 x 4 /i. Very common on cowpea leaves in circular spots, with dark pycnidia in concentric circles on white background. 364 PLANT DISEASE FUNGI Dothichiza Libert (p. 363) Pycnidia erumpent, roundish, somewhat disculate, irregularly dehiscent; conidia elongate or cylindric. In part=Cenangium. D. populea S. & B. parasitizes poplar. Sporonema Desmazieres (p. 363) Pycnidia subepidermal, erumpent, at first closed, then opening radiately; conidia ovate or cylindric. S. platani Bauml. on Platanus=Gnomonia veneta. Seep. 196. S. phacidioid.es Desm. = Pseudopeziza trifolii. See p. IIL S. oxycocci Sh. Pycnidia amphigenous, excipuliform, thick- ened at the base, gradually disappearing above, immersed, erumpent, depressed-glo- bose, gregarious or scattered, 50-100 fx, some- times collapsing, rupturing irregularly by a Fig. 335.-Sporonema oxy- slit or triangular spht; conidia cylindric, After sheaT°^'"^ ^^^^' Straight, 17-19 X 3-4 /x) conidiophores simple, oblong to subglobose, about one fourth the length of the spore or less. On cranberry. S. pulvinatum Sh. is also on cranberry. Melanconiales ^ (p. 334) Mycelium internal; true pycnidia never developed, the conidio- phores form a stratum; strata typically bearing conidia in acervuli which are immersed or erumpent, black or light colored, waxy, corneous or even submembranous, accompanied by setae or not; conidia variable. The common name '^anthracnose" is applied to any disease caused by a member of this order. A single family Melanconiaceae, which contains about forty-five genera and over twelve hundred species. Melanconiaceae-Hyalosporae Conidia hyaline, 1 -celled, globose to oblong, rarely dilute colored. lEdgerton, C. W. The Melanconiales. Trans. Amer. Mi. Soc. 31: 243, 1912. PLANT DISEASE FUNGI 365 Key to Genera of Melanconiaceae-Hyalosporae Conidia muticate Acervuli not setose Conidia not catenulate; masses gray to black, rarely bright colored, waxy or horny Growing, for the most part, on leaves or fruits 1. Gloeosporium, p. 365. Growing usually on twigs of trees or shrubs 2. Myxosporium, p. 368. Acervuli setose at margin; conidiophores short, fasciculate 3. CoUetotrichum, p. 369. Gloeosporium and CoUetotrichum are prominent in pathology as the "anthracnose fungi" and cause many important diseases. The two genera, distinguished only by the occurrence or non-occurrence of setae, contain many species which have been transferred from one of these genera to the other on this character, which is to some extent a variable one depending upon the supporting medium, con- ditions of growth and the particular strain of the fungus under observation. Many form-species have been described solely on a basis of the hosts affected. Subsequent culture study, and cross inocula- tion has often failed to sustain these species so that many forms that were formerly considered as distinct are now grouped under one name. No satisfactory disposition of these forms can be made until their ascigerous stages are known and compared and their biologic relations investigated. Such work as has been done (see page 190) leads rather to con- solidation than to segregation of species. For sake of clearness and convenience, mention is made below of many form species of these two genera under their old names, though the evidence now is that in many instances they should be consolidated with other species. Gloeosporium Desmazieres & Montaigne Conidial layer subepidermal, disciform or pulvinate, usually erumpent, pale or fuscous; conidia ovate, rarely oblong; conidio- phores needle-shaped. In part=Glomerella, Pseudopeziza, Gnomoniella, Gnomonia^ Trochila, Physalospora, Calospora. 366 PLANT DISEASE FUNGI There are several hundred species, many of them very impor- tant pathogens. The spores in germination commonly form dark colored, thick-walled chlamydospores and usually become 1-septate. G. rufomaculans (Berk.) Thiim. on a large variety of hosts, G. fructigenum Berk, on many fruits, G. ribicolum E. & E. on Ribis, G. rubi E. & E. on Rubus, G. psidii on guava, G. laeticolor Berk, on peaches and apples and G. versicolor B. & C. on peaches, G. cingulatum Atk. on privet, are probably identical with Glomerella cingulata. See p. 190. G. salicis West, on Salix=Pseudopeziza salicis. G. piperatum E. & E. on pepper= Glomerella piperata. See p. 194. G. cylindrospermum (Bon.) Sacc. on Alnus=Gnomoniella tubi- formis. G. vanillae Cke. on orchids =Calospora vanillse. G. macropus Sacc. on Cattleya=Physalospora cattelyse. G. cinctum B. & C. on orchids = Glomerella cincta. G. paradoxum (de Not.) Fcl. on Hedera=Trochila craterium. G. atrocarpi Del. on At rocarpus= Glomerella atrocarpi. G. nervisequum (Fcl.) Sacc. on sycamore=Gnomonia veneta. See p. 196. G. ribis (Lib) M. & D. on Ribes= Pseudopeziza ribis. See p. 111. G. caryae E. & D. = Gnomonia caryse. G. ampelophagum. (Pass.) Sacc. = Sphaceloma ampelinum. Spots subcircular often confluent, from cortex of the berry, cen- ters gray; margin dark or red. Acervuli subepidermal, minute, col- lected; conidia oblong, ellipsoid or ovoid, 5-6 x 2-3 m, hyaline. Small dark spots are produced on fruit, leaf or cane of grape. These later enlarge and show white centers with dark or even red borders. The mycelium lies just below the epidermis. On shoots the cambium is killed and cankers develop. An ascigcrous stage had been reported in Europe as Manginia. G. musarum Cke. & Mass. is a common wound parasite on bananas. Acervuli innate, crumpent, gregarious, rose-tinged; conidia elongate-ellipsoid, ends rounded, 10-12 x 4-5 /jl, granular. G. trifolii Pk. Spots subcuticular, brown, suborbicular, concentrically zonate; conidia oblong to cylindric, obtuse, 15-23 x 4-6.3 /x. The cause of dying of stems and leaves of clover. PLANT DISEASE FUNGI 367 G. caulivorum Kirch. Caulicolous, spots forming long dark streaks, more or less sunken, blackish-bordered; acervuli minute; conidia curved, more or less pointed, 12-22 x 3-5 /jl. The cause of serious anthracnose affecting stem, fruit and leaf of clover. G. medicaginis E. & K. Acervuli scattered, innate, blackish, rather large, visible on both sides of the leaf, opening below; conidia oblong, cylindric, granular, subhyaline, more or less narrowed at the middle, 15- 30 X 3-4 fi. On withered leaves and stems of alfalfa, defoliating the lower part of the stem. G. juglandis (Lib.) Mont, causes a common and serious leaf blight of the butternut. G. fagi (D. & R.) West, is on beech. Spots subcircular, fuscous above, olivaceous, vitreous be- neath; acervuli small, prominent, honey-colored; conidia oblong ovate, 15-20 x 7-8 /z, minutely 1 to 3-guttulate; conidiophores fasciculate, cylindric, fuscous. G. apocryptum E. & E. causes a nursery disease of maples and of box elder. Acervuli numerous, minute, mostly hypophyllous, on dead areas of the leaf; conidia very variable in size, 5-12 x 2.5-5 fx, oblong to narrowly elliptic. G. betularum E. & M. Spots rounded, 2-3 mm., blackish margined; acervuli amphig- enous, brownish, 120-140 jjl, becoming cupulate; conidia hyaline, obovate, 9-10 x 5-6 fi. It is common on leaves of American birches. G. ulmicolum Miles. Spots epiphyllous, raised, gray, elongated, following the leaf veins, often extending the entire length of the secondary veins which have become browned far beyond the limits of the spot; acervuli epiphyllous, gregarious, subcutaneous, covered by the persistent, darkened cuticle which finally ruptures irregu- larly to allow the dispersal of the spores, averaging 800 /jl in diame- ter, irregular in outline but usually elongated suborbicular; conid- iophores in a closely packed layer, dilute-brown, cylindrical, on a pseudo-parenchymatous, colorless hymenial base, 10-15 x 2-3 /x, terminating in a sterigma-like projection on which the spores are borne; conidia hyaline, one-celled, straight, rounded at both 368 PLANT DISEASE FUNGI ends, oblong-cylindrical, ovate, elliptical or pyriform, 8-10 x 3-5.5 fx. Parasitic on leaves of elm. Other species have been reported on persimmon, strawberry, almond, cranberry, egg-plant, cucurbits, alfalfa, cabbage, carna- tion, clematis, rose, orchids, Ficus, violet, Pelargonium, Anthur- ium, begonia, oak, elm, palm, linden, beech, ash, birch, butternut, hazel, hickory, horse chestnut, maple, pecan, sycamore, willow, poplar, alder, Carpinus, Corylus, Paulownia, barberry. Myxosporium Link (p. 365) Acervuli immersed or superficial, indefinite, pallid or reddish; conidia ovate, hyaline or pale, conidiophores slender-cylindric. About seventy species, some of which are important patho- gens. In part=Gnomonia. See p. 196. M. valsoideum (Sacc.) All. on sycamore=Gnomonia veneta. See p. 196. M. corticolum Edg. Acervuli erumpent, originating under several layers of cortex, 1-2 mm. in diameter, scattered over the diseased area; conidia Fig. 336. — M. corticolum, on apple twig. After Edgerton. straight or curved, cylindric, very densely granular, 18-36 x 6- 9 /x, oozing out of the pores in white cirri; conidiophores very short. It forms bark cankers in pear and apple in America. M. acerinum Pk. is often fatal to maple trees. Other parasitic species are on Liriodendron, pear, sycamore, apple, conifers, beech, oak, maple. PLANT DISEASE FUNGI 369 Colletotrichum Corda (p. 365) Acervuli innate, erumpent, discoid or elongate, dark, bearing long black seta^; conidia terete to fusoid; conidiophores short. The genus is distinguished from Gloeosporium by the presence of setae, a somewhat unreliable character. See p. 365. In part = Glomerella and Pseudopeziza. See pp. 110, 190. Some eighty species, several of them very important plant pathogens. C. gossypii South, on cotton = Glomerella gossypii. See p. 194. C. lindemuthianum on beans = Glomerella lindemuthianum. See p. 193. C. falcatum Went. Acervuli poorly defined, setse irregularly arranged, cuspidate, 100-200 X 4 /z, brownish; conidia falcate, 25 x 4 /x; conidiophores ovoid, 20 X 8 /x, hyaline to fuscous. This is believed to be the chief cause of the red rot of sugar-cane. C. cereale Manns Spots circular to ovoid, 30 mm.; acervuli dark brown or black; setae few or many, dark brown to black, at base 6-8 /x thick. Fig. 337. — C. cereale, acervulus showing mycelium, setse, conidiophores and spores. After Manns. tapering to a length of 60-120 [i, continuous or 1 to 2-septate; conidia 18-26 x 3-4 fi, spindle to boat-shaped, 2 to several-guttulate ; conidiophores very short, 12-6 x 1-2 /x. This fungus is parasitic on the roots, stems, blades and spikes of rye, wheat, oats, barley, emmer, orchard grass, timothy, blue grass and chess. The disease causes a premature ripening and 370 PLANT DISEASE FUNGI shrivelling of the grain. Superficially the diseased heads present the same appearance as those attacked by scab but no pink over- growth is present, nor is the presence of the disease always appar- ent, as it was found on numerous heads of grain which appeared to be healthy. Morphological studies indicate that all the hosts mentioned above are affected by the same fungus. C. gloeosporioides Penz, ( = Glomerella cingulata) is found on Citrus, causing wither-tip. C. lagenarium (Pers.) E. & H. see p. 194. C. trifolii Bain Spots dark, depressed; acervuli erumpent, scattered or gre- garious; conidia straight, ends rounded, 3^ x 11-13 /x; conidio- phores cylindric or fusoid, hyaline; setae few or many, continuous or uniseptate, dark, paler apically, 4-7 x 39-62 ix, sinuous, or nodose. It occurs as an anthracnose producer on stems, rarely on leaves, of clover and alfalfa. C. spinaciae E. & H. Spots roundish, dirty-white or greenish, 2-4 mm., with a slightly raised border; acervuli amphigenous, punctiform, 40-75 ^, with 3-12 erect or spreading, bristle-like setae, 60-75 x 4-4.5 ^u, sub- bulbous at base, subhyaline, subacute above, dark brown below; conidia subfalcate, fusoid, 2 to 4-guttulate, 14-20 x 2.5-3 /x, ends subacute; conidiophores short. It produces blotches on spinach leaves. C. phomoides (Sacc.) Ches. Spots depressed, circular, slightly discolored, center black, 5-10 mm., later irregular and confluent; acervuli abundant, densely gregarious, rusty brown to black, applanate, 95-150 ix] setae abundant, fuliginous, generally curved, septate, 65-112 fx; conidia oblong, 16-24 x 4 ju, ends subacute; conidiophores short, slender, 30-40 // high, arising from a well developed stroma. On tomato. This is a common cause of ripe rot of tomatoes. C. nigrum, E. & H. Spots blackish, depressed, decayed; acervuli numerous, su- perficial; setae numerous, slender, pointed; conidia oblong. On peppers. C. erumpens (Sacc.) does damage on rhubarb. C. malvarum Br. & Casp. (=C. althaea.) Epiphyllous and caulicolous; spots brown, sunken; acervuli PLANT DISEASE FUNGI 371 erumpent; setae dark brown, abundant, 1 or 2-septate, usually colorless below, 60-109 x 3-5 /z, appearing after the conidiophores which are colorless, cylindric, tapering slightly and apically rounded, slightly longer than the conidia; conidia irregular, oblong, granular, flesh-colored in mass, 1 1-28 x 5 /z. The cause of anthracnose of the hollyhock. C. violae-tricoloris R. G. Sm. Spots pale-yellow on leaves. Dead areas on petals occur with more or less deformity of blossom. Spots at first orbicular and definite, later confluent and irregular, acervuli numerous, 50-150 /i, often confluent; stroma usually poorly developed; setae mostly single or in pairs, 20-70 /z, deep brown, 1 to 2-septate, tapering gradually to a point; conidia oblong or slightly curved, ends blunt, 20 X 5 )Lt; conidiophores short, hyaline. It causes spotting of pansy leaves and consequent failure to bloom. Other species are on grape, turnip, pea, agave, orchids, Anthu- rium, cacao, Ficus, primrose, palms. Aspidistra, snapdragon, Cyclamen, Dracaena, coffee. Melanconiaceae-Phaeosporae Conidia dark, continuous, globose to oblong or fusoid. Melanconium Link Acervuli subcutaneous, conic or discoid, black; conidia not catenulate, elongate to globose-oblong, erumpent in black masses; conidiophore simple. In part=Trichos- phaeria. See p. 160. More than one hundred fifty species. M. fuligineum (Scrib. & Viala) Cav. Acervuli scattered or gregarious, at first gray-cinereous, then brownish, subepider- mal, erumpent; conidia ovoid to ellpisoid, inequilateral, acute 9-12 x 4-6 yu, olive, guttulate; conidiophores filiform, from a well developed stroma. Fiq. 338.— m. fuligineum. It causes the important bitter rot of ripening grapes, especially the white varieties, occurring also on shoots and peduncles. Acervuli appear on the surface of the rotted berries. The mycelium penetrates even to the seeds. 372 PLANT DISEASE FUNGI M. pandani Lev. is common on Pandanus in greenhouses, kill- ing the branches. M. sacchari Mass. Acervuli numerous, collected' in indeterminate, pallid, orbicular spots; conidia cylindric, 10-15 x 3-4 tx, straight or slightly curved, olivaceous, smooth. In leaves, sheaths and culms of sugar cane. M elanc oniac eae-Hy alodidymae Conidia hyaline, 1-septate, ovoid to fusoid. Marssonina Fisch. Acervuli globose-discoid, pale, conidia ovate to elongate, mu- ticate. In part=Gnomonia, Trochila, Pseudopeziza. Some seventy-five species, all leaf parasites, several of economic importance. M. castagnei (D. & M.) Sacc. on poplar = Trochila popu- larum. M. juglandis (Lib.) Sacc. on walnut =Gnomonia leptostyla. See p. 198. M. populi (Lib.) Sacc. Spots suborbicular, epiphyllous, separate or confluent, brown, '^3£JcSrSc2< Fig. 339. — M. panattoniana, cross section of an acervulus. After Brandes. darker margined, acervuli convex to applanate, fulvous; conidia obovate to subpyriform, 20 x 12 fx, constricted at the septum, straight or curved. On poplar, injurious in nurseries. PLANT DISEASE FUNGI 373 M. panattoniana (Berl.) Mag.^=Marssonia perforans E. & E = Didymaria perforans (E. & E.) Dandeno. Spots small, irregular, 1-2 mm., pale, soon deciduous; acervuli 100- 120 n, or by confluence larger; conidia abundant, clavate or wedge shaped, 11-15 X 2.5-3 M. The cause of leaf perforations of lettuce. M. violae (Pass.) Sacc. Discoloration of the host slight, acervuli numerous, scattered, small; conidia curved or straight, 15-18 x 5-6 /x, septum usually excentric. Small spots are produced on violet Fiq. 340.— Marssonina violgeT^ores l/Amrz-vo and conidiophores. After J.ones ani leaves. Giddlngs. Others are on strawberry, rye, rose, oak, ash, butternut, chestnut, hickory, poplar, walnut, willow Melanconiaceae-Hyalophragmiae Conidia hyaline, 2 to several-septate, oblong to fusoid or cla- vate. Fig. 341. — Septogloeum acerinum, conidiophores and conidia. After Sac- cardo. Septogloeum Saccardo Acervuli very small, subepidermal, erum- pent, pallid; conidia oblong, separate, mu- ticate. Some twenty -five species of leaf parasites. S. profusum (E. & E.) Sacc. Spots epiphyl- lous, flavous; acervuU scattered, hypophyl- lous, large; conidia issuing in white cirri, cylindrical, oblong, granular, 3-septate, 25- 30 X 6-7 M- On living leaves of elm and on Corylus americana. S. hartigianum Sacc. attacks maple, kill- ing very young twigs. S. cydoniae (Mont.) Pegl. is on the quince; S. fraxini Hark, on ash. ^ Brandes, E. W. Anthracnose of lettuce caused by Marssonina panattoniana. Jour. Agr. Res. 13: 271, 1918. 374 PLANT DISEASE FUNGI Melanconiaceae-Phaeophragmiae Conidia dark, 2 to several-septate, oblong to cylindric. Key to Genera of Meianconiaceae-Phaeophragmiae. Conidia muticate Conidia not in chains, oblona;, not stellate, not rostrate, not protruded in cirri 1. Coryneum, p. 375. Conidia ciliate at apex Conidia 1-ciliate 2. Hyaloceras, p. 374. Conidia several-ciliate 3. Pestalozzia, p. 374. Hyaloceras Dur. & Mont. Monochaetia Sacc. As in Pestalozzia except that the conidia bear only a single seta. About sixty species. H. pachysporum (Bub.) Bub. is common on chestnut causing large, circular, dead leaf spots with the acervuli showing in some- what concentric circles. Pestalozzia de Notaris ^ Acervuli subcutaneous, erumpent, discoid or pulvinate, black; conidia elongate, colored or the endcells hyaline, with several hyaline setae on each end. A genus of over two hundred species of various habit, some of considerable economic importance. P. hartigii Tub. causes disease of tree and shrub seedlings in nurseries, constricting the stem just above the soil and resulting in death. P. funerea Desm. Acervuli scattered, punctiform, Fig. 342. — P. funerea. A. Spores. B. A , , , . , i • i i i young mvceiium. c. Hypha of an older blackish, Subepidermal, erumpcut; mycelium. After Reed. ^^^^^^ dcprCSSOd, whitc; COnidia oblong, fusoid, 5-celled, constricted at the septa, the three central cells fuscous, the others hyaline, 22-32 x 6-8 n, with 2-5 recurved, hyaline spines, 10-15 x 0.7-1 jjl; conidiophores short, 5-9 x 1-1.5 n. ^ Klebahn, H. Zur Kritik einiger Pestalozzia-Arten, Myc. Cent. 4: 1, 1914. PLANT DISEASE FUNGI 375 It is found on various conifers causing disease; also a stem spot of ginseng, girdling the petioles. P. guepini Desm. var. vaccinii Sh. Acervuli minute, punctiform, convex, black, subepidermal, erumpent; conidia elliptic and somewhat unequilateral, about 20 fx long; central cells dark, the two end cells hyaline, the apical cell with 3-4 fihform setae 22-35 /x long, the basal with a short hyaline append- age 6-12 /i long. Common on fallen leaves of cranberries, and associated with rot of the berries. P. uvicola Speg. Acervuli globose, lenticular, black, sub- epidermal, erumpent, 300-400 m; conidia fusiform, 5-celled, the three median oliva- ceous-fuscous, the others hyaline, 35 x 8-10 /x, inferior appendage 25-30 xl jjL, superior group 8-10 x 1 fx. It is described as the cause of rot of grape berries and of a leaf spot on the vine. Others are on sugar cane, calla, rose, fir, palms, willow, Lupinus, eucalyptus, sycamore, linden. Fig. 343. — Pestalozzia guepini vaccinii; V7, a conidium having an apical appendage with three branches; 6, a conidium having an apical appendage with four branches; c, a ger- minating conidium; d, a germinating conidium sending out two germ tubes. After Shear. Coryneum Nees (p. 374) Acervuli discoid or pulvinate, subcutaneous, erumpent, black, compact; conidia oblong to fusoid. C. beyerinckii Oud. = Ascospora beyerinckii, see p. 165. C. foliicolum Fcl. Spots epiphyllous, ochraceous, indefinite; acervuli punctiform, erumpent; conidia eUipsoid-oblong, 17 x 6-7 fi, 3-septate, con- stricted at the septa, olivaceous, lower cell subhyaUne, stalk subhyaline, 15-20 x 1.25 /x. 370 PLANT DISEASE FUNGI It is present as a saprophyte on apple leaf spots. C. tumoricolum Pk. Spots scattered, suborbicular, pale, bounded by a red-brown border. On living leaves of elm. Melanconiaceae-Scolecosporae Conidia cylindric, filiform or suballantoid, hyaline, mostly con- tinuous. Cylindrosporium linger Acervuli subepidermal, white or pallid, disciform or subeffuse; conidia solitary, in mass pale, filiform, continuous, hyaline, straight or curved. About one hundred species of parasites, several of them of con- siderable economic importance. C. mori Berl. on mulberry =Mycosph8erella morifolia. C. castanicolum (Desm.) Berl. on chestnut =Mycosphaerella maculiformis. C. padi Karst. on Prunus=Coccomyces. See p. 117. Fig. 344. — C. padi, section of acervulus. After Pammei. Fig. 345. — C. juglandis, acervulus with conidia. After Wolf. C. chrysanthemi E. & D. Spots subindefinite, 1 cm. or more broad, black; acervuli innate, amphigenous, 100-170 ju; conidia fusoid-straight, 50- 100 X 3-4.5 /x. The fungus causes dark blotches on the leaves of chrysanthe- mum. C. clematidis E. & E. Spots amphigenous, reddish-brown, round or subangular, 1-3 n; acervuH comparatively few, epiphyllous, immersed, scattered; co- PLANT DISEASE FUNGI 377 nidia fusoid-linear, 75-80 x 2.5-3 ix, somewhat curved, exuding in a white mass. It causes leaf spot of Clematis. C. juglandis Wolf causes leaf spot on walnut. Acervuli erump- ent, conidia clavate, many-septate, 20-50 x 3-3.8 [x. C. ulmicolum E. & E. Spots becoming flavous; acervuli mi- nute, hypophyllous; conidia cylindrical, 45-65 x 4 ju, hyaline. On leaves of elm. In spite of the differences in spore measurements, the possibility has been suggested that this is not different from Phleospora ulmi. Others are on hop, lily, maple, alder, birch, elm, hackberry, lo- cust, walnut. Moniliales (p. 334) The Moniliales differ from the Sphseropsidales in the absence of the pycnidium and from the Melanconiales in their somewhat loose, separate hyphse, not innate and closely aggregated as in the Melanconiales. There are genera on the boundaries between these orders which are difficult to place, as for example Coryneum, some species of which are often put in Helminthosporium; Vermicularia which sometimes is confounded with Volutella, etc. The order is one of very great diversity and contains a multitude of forms. Many are only saprophytes while some are aggressive parasites. Key to Families of Moniliales Hyphse in more or less loose cottony masses Hyphse and conidia clear or bright colored I. Moniliaceae, p. 378. HyphsB and conidia typically both dark; one or the other always dark II. Dematiaceae, p. 396. Hyphse compactly united or forming a globose to cylindric body which is often stalked Ilyphal body cylindric to capitate, stalked, i. e., a, synnema or core- mium III. Stilbaceae, p. 416. Hyphal body more or less globose, sessile, i. e., a sporodochium IV. Tuberculariacese, p. 418. 378 PLANT DISEASE FUNGI Moniliaceae (p. 377) Hyphae hyaline or bright colored, more or less fragile, lax, not cohering in fascicles; conidia concolorous, hyaline or bright colored. M oniliac eae- Amer ospor ae Conidia continuous, globose or ovoid to short cylindric. Key to Groups of Moniliaceae-AmerosporaB Hyphae very short or obsolete, little dif- ferent from the conidia Conidia in chains 1. Oosporeae, p. 378. Hyphae elongate and distinct from the conidia Conidiophores simple or little branched, apically swollen, conidia in heads Conidia not in chains 2. Cephalosporieae, p. 379. Conidia in chains 3. Aspergilleae, p. 380. Conidiophores much-branched, conidia not in heads Conidia borne irregularly on simple or branched but not inflated or verticillate conidiophores 4. Botrytideae, p. 384. Conidia borne on verticillately branched conidiophores 5. Verticilliae, p. 389. Oosporeae ^ Conidiophores short or obsolete, conidia in chains. Key to Genera of Oosporeae Conidial chains arising at the apex of the hyphae Conidia globose, elliptic or ovate, all of equal size; sterile hyphae evident; conidia not connected by an isthmus Growing within the substratum ; haustoria none 1. Monilia, p. 379. Growing on the surface of living plants ... 2. Oidium, p. 379. ^ Sumstine, R. Studies in North American Hyphomycetales. The tribe Oosporeae- Mycol. 5: 45, 1913. PLANT DISEASE FUNGI 379 Monilia Persoon (p. 378) Hyphse erect, branched, forming a dense mycelial felt which produces numerous conidiophores; conidia catenulate, hyaline or light-colored, ovate or lemon shaped. Various form species are known to belong to the genus Sclero- tinia. See p. 101. Oidium Link (p. 378) On the surface of living leaves; hyphae branched, white, bearing erect, simple conidiophores with catenulate, ovoid conidia. These conidial fungi in the main belong to the Erysiphacese, (see p. 127) though some forms are placed in Oidium which clearly do not belong to that ascigerous family. Salmon states that there are some forty-four apparently Erysiphaceous Oidiums listed ; but that twenty-five of these grow on plants known to be the hosts of ascus bearing Erysiphaceae. The following unconnected forms may be mentioned: O. erysiphoides Fr. on hop, clover, cucumber, etc.; O. chrysanthemi Rab. on chrysanthemums; O. mespilinum Thiim on Mespilus; O. tabaci Thiim on tobacco; O. verbenas T. & B. on Verbenas; O. quercinum Thiim on oaks. Cephalosporieae (p. 378) Hyphse elongate; conidia in heads. Trichoderma Persoon Sterile hyphse decumbent, cespitose; fertile branches ascending, not inflated at the apex, several times forked; conidia capitate, globose or oblong, sessile on the head. T. koningi Oud. Conidia elliptical, 3-4 x 2.5-3 n. It causes storage rot of sweet potatoes and is also destructive on apple roots. Cephalosporium Corda Hyphse creeping, conidiophores short, erect, not apically swol- len. Conidia spherical or ovate, hyaline or sHghtly colored. 380 PLANT DISEASE FUNGI The small-spored conidial forms often associated with Fusarium (microconidia) belong to this form-genus. Cephalosporium acremonium has been closely associated with a black bundle disease of corn.^ Aspergilleae (p. 378) Hyphae well developed; conidia in heads, catenulate. Key to Genera of Aspergilleae Fertile hyphae inflated at apex, simple or nearly so Sterigmata of apical vesicle none or simple; conidia terminal on sterig- mata 1. Aspergillus, p. 380. Sterigmata verticillately branched 2. Sterigmatocystis, p. 380. Fertile hyphae little or not at all inflated, verticillately branched at tip; tips unequally verticillate; conidia glo- boid, without mucus; conidiophores slender 3. Penicillium, p. 381. Aspergillus (Micheli) Link Hyphae effused, creeping; conidiophores erect, simple, capitate; conidia catenulate; sterigmata none or indistinguishable from the conidia. The conidia are often found, the asci but rarely. A. ficuum (Hen.) Weh. and A. phoenicis (Cda.) Lind. occur on figs. A. niger v Tieg.^ occurs on onions. Grove erects a new genus Rhopalocystis,^ for this species, based on the fact that its color should place it in the Dematiaceae. Fig. 34(J. — Aspergillus. From Strassburger et al., Text Book of Botany. Sterigmatocystis Cramer As in Aspergillus but with the sterigmata branched in whorls at the apex. S. castanea Pott, causes an internal rot of pomegranates. ^ Reedy, C. S. Holbert, J. R., The black-bundle disease of corn. Jour. Agr. Res. 27: 177, 1924. ^Thom, Charles. Aspergillus niger group. Jour. Agr. Res. 7: 1, 1916. 3 Grove, W. B. Four little-known British fungi. Jour. Econ. Biol., 6: 38, 1911. PLANT DISEASE FUNGI 381 Penicillium Link ' (p. 380) Hyphse creeping; conidiophores erect, apically irregularly ver- ticillate-penicillately branched; conidia catenulate, spherical, or elliptical, hyaline or variously colored. For the ascigerous stage see page 125. The species within this form genus are generally difficult of description and recognition requiring their culture on media of definite composition under strictly controlled conditions, ob- servation of the habit, structure, and appearance of the colony on two different, standard media and of the physiological effects of the colony upon these media, as well as full note of habit and morphology. Many of the forms are cosmopolitan and indiscrimi- nate saprophytes. The two species given below as on oranges are, however, characteristic of this substratum. The following de- scriptions are taken from Thom. P. expansum Link (in part), emend Thom, = Coremium glau- " W' '!'■'"■ i. Fig. 347. — P. expansum Link: a, b, f, branching and arrange- ment of branches of conidial fructification; c, d, e, conidiifer- ous cells and conidial chains; g, h, j, k, 1, sketches of fructifi- cation; m, n, o, germination of conidia. After Thom. cum Link. = Penicillium glaucum Link (in part), = Coremium vulgare Corda (in part). Colonies upon gelatine and potato or bean agar, green becoming gray-green and slowly brown in several weeks, floccose, with con- centric zones tufted with short, loose, coremium-like aggregations ^Thom, C. Cultural studies of species of Penicillium. U. S. Dept. of Agr. Bur. Animal Ind. Bui. 118, 1910. 382 PLANT DISEASE FUNGI of conidiophores, not over 1-2 mm. in height except in old cultures containing sugar, broadly spreading with broad white margin in growing colonies. Reverse somewhat brown. Conidiophores either very short lateral branches of serial hyphse or very long, 1 mm. or more, arising singly or grouped with others to form coremia. Conidial fructifications consist of 1 to 3 main branches bearing verticils of branchlets supporting crowded whorls of co- nidiiferous cells, 130-200 x 50-60 ix at base, in cultures without sugar; in sugar media continuing for some weeks to produce great number of conidia which come to form masses perhaps 1 mm. in thickness. Conidiiferous cells 8-10 x 2-3 /x. Conidia elliptical to globose, 2 x 3.3 or 3-3.4 //, green, homogenous, persisting in chains when mounted. Colonies begin to liquefy gelatine slowly after about 10 days and continue until it is completely liquefied. It occurs characteristically upon decaying apples and other pomaceous fruits, where old colonies often produce coremia 1 cm. or more in length and very large. Thom further states: " I find there is a group of strains giving the general morphology and general physiological reactions described by me under the name expansum. These organisms vary somewhat in their rate of activity, slightly in color of spore area and more considerably in the colors induced in the substratum, yet they have an essential homogeneity in the cultural picture. The difficulties of separating these organisms into identifiable species have led me thus far to hold the nomenclature last used, P. expansum, for the entire lot. It has been possible to produce some rot in apples by organisms outside this group but the amount of rot so induced and the ob- servations that I have made in the rotten-apple barrel do not lead me to believe that under ordinary conditions in storage the Penicillia outside the P. expansum series are of great importance." Many citations in the literature to P. glaucum Link and P. crustaceum (L.) Fries refer to this species. P. italicum Wehmer Colonies on plain gelatine and potato or bean agar bluish green, becoming gray-green when old, broadly spreading, aerial portion composed at the broad margin almost entirely of conidiophores, but becoming slightly floccose in the center. Reverse of colonies dark brownish, often almost black in media containing sugar. Conid- iophores from short, 100 /z, to very long, 600 Mj averaging per- PLANT DISEASE FUNGI 383 haps 250 M, arising either directly from substratum or as branches of aerial hyphae. Conidial fructifications up to 300 /x or more in length, consisting usually of a main branch and one lateral branch, each producing a whorl of branchlets bearing crowded verticils of conidiiferous cells, 12-14 x 3 /i. Conidia breaking off in masses in handling old cultures, which rise in clouds when shaken. Chains of conidia loosely divergent, long; conidia 2-3 X 3-5 )U, cylindrical to ellip- tical or slightly ovate, clear green by transmitted light. Masses of spores continue to increase from 2 to 3 weeks. Petri-dish colonies partially and slowly liquefy gelatine (12 to 20 days). Numerous white sclerotia are produced upon the sur- face of the medium after 2 to 3 weeks' growth, espe- cially upon fruits and other acid media rich in sugar. Cosmopolitan ; character- istic of decaying oranges, which become bright blue- green with this mold as contrasted with the olive- green species which is often Fig. 348.— p. italicum; a, b, c, d, e,f, U, types of ^ • 1 • 1 • 1. branching formation of verticils of conidiiterous associated with it upon the cells and comdlal chains, j, k, sketches of conidial » . . fructifications; I, m, n, swelling and germination same irUlt. of conidia. After Thorn. P. digitatum Sacc. Colonies on sugar gelatine and potato or bean agar grayish olive, irregularly shaped from the unequal growth and branching of rather few hyphae; serial portion consisting only of very short conidiophores and conidia. Reverse of colony commonly brown to black. Conidiophores rising directly from the substratum, 30- 100 X 4-5 fx, usually very short. Conidial fructification a few tangled conidial chains up to 160 m in length, borne upon conidi- iferous cells 13-16 X 3-4 fi. Conidia cylindrical to almost globose, 384 PLANT DISEASE FUNGI 4-7 X 6-8 iu, often uneven in size and shape in the same chain. Colonies do not liquefy sugar gelatine except occasionally in old cultures; litmus reaction acid; grows readily on organic media, Fig. 349. — P. digitatum: a whole conidiophore and fructification; b, c, d, e, types of branching and formation of conidia; m, n, o, germination of conidia. After Thom. but shows a very pronounced affinity for such media with high percentages of sugar, in which it produces a strong odor. Refused to grow in synthetic media containing nitrogen as sodium nitrate. Cosmopolitan upon citrus fruits, distinguished from P. italicum by the sharp contrast of its olive color with the blue of the other. Botrytideae (p. 378) Conidiophores elongate, simple or branched but not inflated, and the branches not verticillate ; conidia borne variously, globose or ovate to elliptic. Key to Genera of Botrytideae Conidia smooth or scarcely roughened, acrogenous or pleurogynous, intermediate joints of the conidiophores equal, conidia- bearing hyphse of one sort only PLANT DISEASE FUNGI 385 Fertile hyphae simple or nearly so, hyphse not denticulate; conidia solitary, sterile hyphae within the host 1. Ovularia, p. 389. Fertile hyphse branched; conidia globose to ovoid Both sterile and fertile hyphae procum- bent; sterile hyphse superficial, fer- tile hyphae vaguely branched ; conidia acro-pleurogynous 2. Sporotrichum, p. 385. Fertile hyphae erect or ascending; conidia loosely grouped about the apex, not involved in mucus; apices not muricu- late or inflated 3. Botrytis, p. 385. Sporotrichum Link Hyphse widely spreading, much branched; conidiophores simple, short ; conidia solitary or in groups on separate sterigmata, ovoid or subglobose. Over one hundred twenty-five species are described, most of which are saprophytes. S. poae Pk. Hyphse creeping, interwoven, branched, continuous or sparingly septate, variable in thickness, 2.5- 6 fjL, hyaline, forming a loose cot- tony stratum; conidia of two kinds; microconidia, globose or broadly ovate, 4-12 ii; macroconidia abun- dant, elongate elliptic to ovate ellip- tic, 1, rarely 2- septate, about three or four times as large as the micro- conidia. The form is an atypical one in that it produces two kinds of spores; one kind which is usually septate. It is the cause of bud rot of car- nations; also found in connection with a disease known as ''silver top" of June grass in which the panicles wither as they expand. Botrytis (Micheli) Link Hyphse creeping ; conidiophores simple or more or less markedly dendritic branched, erect, branches various, thin and apically Fig. 350. — S. poae. 11, Hypha bearing conidiophores and macroconidia. 13, Hypha bearing conidiophores and microconidia. After Heald. 386 PLANT DISEASE FUNGI pointed, thick and obtuse or cristate; conidia variously grouped at the apex of the branches, never in true heads, continuous, globose, elliptic or oblong, hyaline or light colored. In part=Sclerotinia. See p. 101. A genus of some two hundred or more species, several of them of great economic importance. This form-genus contains many parasites on various hosts. In some instances they are known to include ascigerous stages, Sclerotinia, in their life cycle; in others no such relation is known, though it has often been assumed on quite untenable grounds. Specific limitations are but poorly understood and the relations between the various forms and between these forms and the as- cigerous stages are in a state of much confusion (c. f. p. 101). In some instances the same conidial stage is claimed by different in- vestigators as belonging to two distinct ascigerous species, a manifest impossibility, e. g., S. fuckeliana and S. sclerotiorum with B. cinerea. The more prominent forms as described are given below, recog- nizing that some of them may be co-specific. B. cinerea Pers.^ Hyphse slender, constricted at septa, gregarious, simple or sparsely branched, erect, cinereous; conidia globose, pale. On the lily, Ward, in a classic study demon- strated the parasitism of the fungus showing its action to be dependent upon toxins and enzymes. No ascigerous stage was found. The fungus has also often been reported on the cul- tivated geranium, dahlia, cyclamen, primrose. On lettuce Humphrey, Jones, Bailey, and many others have reported a mold on the leaves due to a Botrytis which is often cited as B. cinerea. The affected part of the leaf collapses and is covered with a conspicuous growth of the conidiophores and conidia. On lemon trees it produces gummosis. Other hosts are rose, various conifers, grape, Prunus, bean, horse chestnut, Douglass fir, pine, spruce, larch, hemlock. On strawberries it penetrates all parts of the berry dissolving Fig. 351. — B. cineroa. After Smith. ^ Brown, Wm. Studies in the physiology of parasitism. I. The action of Botry- tis cinerea. Ann. Bot. 29: 313, 1915. PLANT DISEASE FUNGI 387 the middle lamellae and passing between the cells for considerable distance or penetrating the cell walls. Numerous studies of the power of B. cinerea to infect growing tissue have been made with the con- clusion that it is a weak parasite and that to be- come aggressively parasitic it must first develop a vigorous mycelium saprophytically. Attempts to immunize plants against its attack have been made with partial success. B. poeoniae Oud. Mycelium in the parenchyma of the host, hyphse erect, 0.25-1 mm. high, protruding through the stomata, branches spirally arranged, simple or branched; conidia numerous in heads 12-15 fx across, oblong or ovate-oblong, 16-18 x 7-7.5 ^i, hyaline or dilute colored. It is reported as the cause of considerable in- Fig. 352.-B. tuijpi jury to peonies in different parts of the United States. The greenish-black, flat sclerotia are found inside the stems. a conidiophore with several clus- ters of conidia. After Hopkins. Fio. 353. — B. tulipse, showing at- tachment of the conidia to the conidiophores. After Hopkins. FiQ. 354. — B. tulipse, microconidia. After Hopkins. 388 PLANT DISEASE FUNGI B. tulipae (Lib.) Hopkins.^ B. parasitica Cav. Lesions occur on bulbs, leaves, petals and stalks of tulips. The mycelium is usually intercellular where it passes throug;h the host tissue in advance of the death of the host cells, while in older parts of a lesion where the cells are dead it is intracellular. Though the cells are not killed immediately by the mycelium, evidences of disease are seen in advance of the mycelium indicating toxic or enzyme action. Infection occurs both with mycelium and with conidia without previous wound. Fig. 355. — B. tulipae, showing mycelium both inter- and intracellular. After Hopkins. Mycelium variable in diameter, often anastomosing, branches not constricted at the base; conidiophores arising directly from the mycelium, erect, brown, proliferating, twisting on their axils when dry, slightly swollen at the base, dichotomous, apices swollen; conidia large, 12-24 x 10-20 /z, obovate, reddish brown in mass; microscopically gray to hyaline, smooth, with a short stalk, often or commonly not remaining attached; sclerotia at first white, finally black, small, 1-2 millimeters in diameter, circular or some- what elliptical, flattened vertically and often convex; microconidia globose, about 3 ^t in diameter, occurring on special, penicillate, obclavate conidiophores arising in white tufts from the substratum. ^ Hopkins, E. F. The Botrytis blight of tulips. Cornell Agr. Exp. Sta. Mem. 45, 1921. PLANT DISEASE FUNGI 389 B. aim Mimn Conidiophores numerous, septate, erect, usually about 0.5 mm., high, occurring either singly or in clusters, not often branched on the host plant; conidia-bearing on upper portion, conidial clusters approximate; conidia hyaline or dilutely colored, elliptical, often slightly tapering at both ends, 7-16.2 x 4-6 ix, attached by a short sterigma to the vesicles in small clusters; sclerotia dull- black, firm, white inside, flattened or concave below, strongly convex above; single sclerotia 1-5 mm. in diameter, usually several to many united in clusters or crusts which may be several centi- meters in diameter. The sclerotia germinate by hyphse which immediately produce conidiophores. No apothecia are produced. Parasitic on leaves, flowers, and bulbs of onion. Other reported hosts of Botrytis are Citrus, Prunus, raspberry, snowdrop, gooseberry, persimmon, egg-plant, lilac, lily-of-the- valley, carnation, dahlia, geranium, orchids, peony, primrose, golden seal, hemlock, horse-chestnut, larch, linden, pine, spruce, sycamore. Ovularia Saccardo (p. 385) Hyphse simple or sparingly branched, erect, apically simple or dendritically branched; conidia globose or ovoid, solitary, rarely in short chains. Over seventy-five species, all parasites. O. canaegricola Hen. is on economic species of Rumex. O. armoraciae Fcl. on horse radish. O. interstitialis B. & Br. and O. primulana Thiim. on primrose leaves; others are on Vicia, primrose, alder, willow, lemons, lilac, alfalfa, clover. Verticilleae (p. 378) Conidia acrogenous, on verticillate branches of the conidiophore. Key to Genera of Verticillieae Conidia solitary or loosely grouped, not in chains; conidia-bearing branches not very short; conidia globose to ovoid, tips of branches not in twos rectan- gularly; conidia not conglutinate, separating readily from the tips 1. Verticillium, p. 390. Conidia capitate, not in chains, sessile, in- volved in mucus, fertile hyphse smooth. 2. Acrostalagmus, p. 390. Fig. 356. — Ovularia. After Sorakin. 390 PLANT DISEASE FUNGI Verticillium Nees (p. 389) Hyphae creeping; conidiophores erect, verticillately branched; conidia borne singly at the apex of the branchlets, globose-ovoid, hyaline or light colored. A form genus of some seventy-five species consisting in the main of conidia of various species of Hypocreales. See p. 145. V. albo-atrum Reinke & Berthold.^ Conidia elHpsoidal, unicellular, 4-11 x 1.7-4.2 jjl, cut off singly from the sterigma tips of verticillate conidiophores; primary whorls of branches, 1-8 in number, 30-90 ^i apart, sometimes bearing secondary virtels; branches 1-7, usually 3-5, in number, 13-38 fjL long, tapering, straight to slightly bowed; conidiophores 100-300 II or more in length. The terminal branch of the conidi- ophore is from 15-60 n long. Conidia may or may not be collected in heads on the sterigma tips. Mycelium septate, hyaline to brown with age, sometimes swollen into chlamydospore-like chains of closely septate, knotted masses. These constitute the sclerotia. It is a vascular parasite, the cause of a wilt of okra, potato, egg- plant, cotton, snapdragon, and probably of species of Abutilon and Xanthium, ginseng, black raspberry, China aster, and dahlia. On potato the vessels are browned into the tips of stems and into petioles. Acrostalagmus Corda (p. 389) Hyphse creeping; conidiophores erect, septate, richly verticil- lately branched; conidia borne in slimy heads on the enlarged ends of the secondary branches. Both of the fungi given below as in this genus may be identical with Verticillium albo-atrum. A. albus Preu. Hyphae cespitose, effuse, slen- der, subangular, continuous or septate, conidiophores, 200-220 X 1.7-2 JJL, erect; fertile branches Fig. 357. — Cross-section of a vascular bundle. . . x • i i i Acrostalagmus threads in the vessels. After COUtmUOUS, Straight Or CUrVCQ ; Van Hook. couidia iu spherical heads, 9-10 ii in diameter, numerous, minute, elliptic oblong, 3.3-3.4 x 1-1.5 /i, hyaline. ^ Carpenter, C. W. Wilt diseases of okra and the Vertieillum-wilt problem. Jour. Agr. Res. 12: 537, 1918. PLANT DISEASE FUNGI 391 It causes a wilt of ginseng. The vascular bundles are yellowed and the ducts plugged by the mycelium. Entrance is apparently through the leaf scars. A. caulophagus Law. Tufts 1-3 mm. tall, forming long, floccose, irregular or short, thin, flaccid and arachnoid patches; conidiophores hyaline, 100-830 ju long, non-septate; laterals grouped or single, bearing one or two sets % of numerous, short, simple, forked or whorled branches bearing heads of conidia; mycelium profusely septate, hyaline or olive-brown, 3- 4 /x broad; chlamydospores spherical or oblong, single or in chains, 7-12 ^ in diameter; heads of conidia hya- line, smooth, round 7.5-25 /x, bear- ing numerous conidia imbedded in a mucilaginous matrix that is readily soluble in water; conidia hyaline, oblong to oval, sometimes biguttulate, 3-7.5 x 2-3 ^u Parasitic in the stems of the black raspberry. Fig. 358. — Spore-bearing stalks of Ac- rostalagmus albus. The spores are borne in heads and are held together at first by a coat of slime. After Van Hook. Moniliaceae-Didymosporeae Conidia hyaline or bright colored, 1-septate, ovoid oblong or short fusoid. Key to Genera of Moniliaceae-Didymosporeae Conidia not obliquely beaked. Conidia smooth, capitate at apex of conidiophores Fertile hyphse simple 1. Cephalothecium, p. 392. Fertile hyphae dichotomously branched, sterigmata subternate 2. Cylindrocladium, p. 392. Conidia echinulate; conidial cells mi- equal 3. Mycogone, p. 392. Conidia obliquely beaked 4. Rhynchosporium, p. 393. 392 PLANT DISEASE FUNGI Cephalothecium Corda (p. 391) Hyphse prostrate; conidiophores erect, simple, septate; conidia apical, subcapitate, oblong to pyriform, hyaline. C. roseum Cda. Cespitose in subrotund, rose colored spots, fading with age, byssoid; hyphse creeping, branched; conidiophores erect, simple, continuous, hyaline; conidia oblong-ovate, constricted at the septum, capitate, light rose. It is often found following apple scab gaining entrance through the in- jured cuticle and causing rot. A ring of pink conidiophores and conidia is formed around the margin of the scab. Inoculation tests showed the fungus unable to penetrate through sound cuticle though it readily made entrance through wounds. It has been occasionally reported on living twigs and leaves. FiQ. 359. — Spores of Cephalothe- cium roseum. After Eustace. Cylindrocladium Morgan (p. 391) Sterile mycelium creeping; fertile, erect, dichotomously or trichotomously branched; sterigmata on the tips of the branches in pairs or threes ; conidia cylindrical, 1 -septate, hyaline. C. scoparium Morg.^ Conidiophores see Fig. 360; conidia cylindrical, tapering, 1-septate, 40-50 x 4-5 jjl. It causes canker on rose stems. Mycogone Link (p. 391) Hyphifi intricately branched; conidiophores short, lateral ; conidia unequally 2-celled, the upper larger, echinulate. ^ Anderson, P. J. Rose cancer and its control. Mass. (Amherst) Agr. Exp. Sta. Bui. 183, 1918. Fig. 300. — C. scoparium. conidiophores and co- nidia. After Anderson. PLANT DISEASE FUNGI 393 There are about fifteen species of mycogenous fungi which are probably conidial stages of Hypomyces. M. perniciosa Mag. White throughout, byssoid, deforming the host; conidiophores short; conidia soUtary, more or less pyriform, almost colorless, 17- 22 X 9-12 fx. It is reported as the cause of a mushroom disease in America. A VerticiUium conidial stage was present but no ascigerous form. M. rosea Link also occurs on mushrooms. Rhynchosporium Heinsen (p. 391) On leaf spots; hyph^ filiform, hyaline, creep- ^ZnilS^^^-^refZlTo: ing, septate; conidiophores erect, with in- ii^dia. After saccardo. curved branches, hyaline, apically denticulate; conidia short-cylindric, with short obHque beak, medially septate, hyaline. R. secalis (Heins) Davis=R. graminicola Heins. This occurs on rye, wheat, and barley. Spot oblong, 0.5-2 cm. long; conidia 13-19 x 3.6 m, hyaline, 1 -septate. Moniliaceae-Phragmosporae Conidia hyaline or bright colored, 2 to several-septate, oblong, fusoid or elongate. Key to Genera of Moniliaceae-Phragmosporae Fertile hyphse very short and little dif- ferent from the conidia; conidia in chains, cylindric or oblong 1. Septocylindrium, p. 393. Fertile hyphse manifest and distinct from the conidia; conidia not mucose- conglobate Conidia ovate-cylindric or elongate, often catenulate 2. Ramularia, p. 394. Conidia obclavate-pyriform 3. Piricularia, p. 395. Septocylindrium Bonordin Conidiophores very short, scarcely distinct from the conidia or in parasitic species distinct but short and inflated or dentic- 394 PLANT DISEASE FUNGI ulately sublobate at the apex; conidia oblong or cylindrical, one to many-septate, catenulate, the chains often branched. S. areola (Atk.) P. & C. Spots amphigenous, pale, becoming darker in age, 1-10 mm., angular, limited by the veins of the leaf, conidiophores amphig- enous, fasciculate, sub- nodose, branched or not, several times septate, hyaline, 25-75 x 4-7 /x; conidia oblong, usually abruptly pointed at the ends, catenulate or not, 14-30 X 4-5 M, hyaline. Leaf spots are pro- duced on cotton. The conidia and stalks are so abundant on the un- dersides of spots as to give them a frosted appearance. S. rufomaculans (Pk.) P. & C. Spots numerous or confluent and even covering the entire leaf, reddish; conidiophores very short, hypophyllous, cespitose; conidia catenulate, variable, ellipsoid-oblong to cylindric, hyaline, 8-16 x 3-4 /i. It is somewhat injurious on buckwheat. Fig. 362. — S. areola. After Atkinson. Ramularia linger (p. 393) Conidiophores fasciculate, simple or with short, scattered branchlets, often flexuose, nodulose or denticulate towards the apex, hyaline or light colored; conidia acrogenous or acropleuro- genous on the denticulations, hyaline, sometimes subcatenulate, oblong, cylindric, typically many-septate. About three hundred species. In part = Mycosphserella. See p. 171. R. tulasnei Sacc. on strawberry = Mycosphserella fragarise. See p. 171. R. armoraciae Fcl. Spots amphigenous, subochraceous becoming gray; conidiophores fasciculate, continuous, subsimple, 40-50 x 2.5-3 /x; conidia rod-shaped, obtuse, hyaline, 15-20 x 3-4 fx. On horse radish causing leaf spots. PLANT DISEASE FUNGI 395 Others are on dandelion, spinach, beet, ginseng, cacao, gera- nium, primrose, violet, Heracleum, sainfoin, artichoke, sweet potato, strawberry. Narcissus, coffee. Piricularia Sacc (p. 393) Conidiophores simple, rarely branched, conidia obclavate to pyriform, 2 to many- septate, solitary acrogenous, hyaline. A small genus of parasites. P. grisea (Cke.) Sacc. produces pallid or water-soaked spots on culms and leaves, with age grayish; conidiophores in clusters of two or five from the stomata, simple or rarely sparingly branched, gray- ish, septate; conidia single, terminal in scorpioid cymes, ovate, 2-septate, 24-29 x 10-12 IX. It causes death of rice plant tissue and the disease called ''blast." If affected fc^ i leaves or stalks are placed in a damp ^^«- 363.— Piricuiana grisea a, ^ , ^ comdiopnores. ,i, gerrmnating atmosphere, for about a day a delicate spores. After Fuiton. grayish fungus, the sporing mycelium, ap- pears. The fungus grows well in culture and applied to the rice plants gives rise to the typical disease spots. It also occurs on millet. ■«--.,. o, , Moniliaceae-Scolecosporae Cercosporella Saccardo Hyaline throughout; conidiophores simple or branched; conidia filiform, many-septate. Dis- tinguished from Cercospora only in color. The genus contains some seventy species of parasites. C. persicae Sacc. Conidiophores cespitose, on discolored areas, filiform, 2 to 3-branched, continuous; conidia 40-60 X 1-5 yu, torulose. The conidia develop in abundance on the lower sides of leaf spots of peach causing a frosty mildew. Others are on Narcissus, lily, parsnip and other Umbelliferse, and on turnip. Fig. 364 After Saccardo. -C. persicae. 396 PLANT DISEASE FUNGI Dematiaceae (p. 377) Hyphse dark or black, cobwebby, loose, usually rigid, not coher- ing in definite fascicles; conidia typically dark and concolorous, but sometimes the hyphae are dark and conidia clear, or the conidia dark and the hyphae clear. This family parallels the Moni- liaceae and certain intermediate forms must be sought in both. Dematiaceae-Amerosporae Conidia continuous, globose to oblong. Key to Subfamilies of Dematiaceae-Amerosporae Conidiophores very short, scarcely distin- guishable from the mycelium Conidia catenulate 1. Toruleae, p. 396. Conidiophores manifest and distinct from the mycelium and spores Conidia dark, rarely subhyaline, in chains 2. Haplographieae, p. 397. Toruleae Conidia in chains. Key to Genera of Toruleae Conidia of two sorts, microconidia in- ternal, catenulate 1. Thielaviopsis, p. 396. Conidia all alike; hyphse hyaline 2. Monilochaetes, p. 397. Thielaviopsis Went. Hyphae creeping, subhyaline ; conidiophores simple, septate; conidia of two kinds; mac- roconidia catenulate, ovate, fuscous; micro- conidia cylindric, hyaline, catenulate within the conidiophore. In part=Trichosphaeria. T. paradoxa (d. Seyn) v. Hohn (=Chalara paradoxa) Macroconidia 16-19 x 10-12 /x; microco- nidia 10-15 X 3.5-5 fx. It is the cause of a pineapple rot and of a sugar-cane disease. In addition to micro and macrospores the fungus possesses a pycnidial form. With variation of the substratum the spores vary Fig. 365. — T. ethaceticus. • i i i c • i After wakker and Went. Considerably irom the typical. PLANT DISEASE FUNGI 397 Monilochaetes Ell. & Hals. (p. 396) Hyphse dark, erect, rigid, septate, not in definite fascicles; conidia distinctly different from the sporophores and hyphse, hyaline, slightly brown with age, continuous, not in chains, acrog- enous. M. infuscans Ell. & Hals.^ On the host definite vegetative hyphse are lacking; sporophores septate, erect, unbranched, dark, and attached to the host singly Fia. 366. — M. infuscans. A, a branched conidiophore with conidia attached. C, a conidiophore from host, with conidium attached. B, an unbranched conidiophore, showing septation; conidium attached. D, a condiophore from the host, showing the pecuUar basal cell and septation. E, a conidiophore from the host, show- ing diagrammatically the attachment to the host by a bulblike enlargement of the basal cell. After Harter. or by twos, by a bulblike enlargement, 40-175 x 4-6 fi, bearing rarely a hyaline, one-celled, oblong spore; conidia 1 -celled, hyaline, ovoid to oblong, 12-20 x 4-7 ijl, solitary, terminal. The causes of scurf disease of sweet potatoes. Haplographieae (p. 396) Conidia dark, catenulate. Hormodendrum Bonorden Hyphse creeping; conidiophores erect, septate, brown, variously dendritically branched; conidia catenulate on the branches, globose, ovoid, olivaceous to fuscous. ^Harter, L. L. Sweet-potato scurf. Jour. Agr. Res. 5: 791, 1916. 398 PLANT DISEASE FUNGI Fio. 367.— H. hordei. After Bruhne. H. hordei Bruhne on barley stems and leaves often reduces the yield. Spots brown, scattered over the entire leaf or confluent, oblong; hyphse simple, septate; co- nidia various, cylindric, rounded or subattenuate, or ellipsoid to subglobose, verrucose. Dematiaceae-Didymosporae Conidia 2-celled, dark, rarely hyaline, ovoid or oblong. Key to Genera of Dematiaceae-Didymosporae Hyphse very short or scarcely different from the conidia Conidia not in chains. 1. Cycloconium, p. 398. Hyphse distinctly different from the conidia ; conidia smooth, muticate, not capitate Conidia more or less catenulate at first Hyphse and conidia uniform, in- flated, somewhat decumbent; conidia short-catenulate or fi- nally solitary 2. Cladosporium, p. 399. Conidia not catenulate Hyphse flexuose-torulose 3. Polythrincium, p. 401. Hyphse not torulose or flexuose, not inflated, usually short and little branched Conidia acrogenous; conidio- phores short, 1 or 2-septate 4. Fusicladium, p. 401. Conidia acro-pleurogenous . ... 5. Scolecotrichum, p. 402. Cycloconium Castaigne HyphsB in the walls of the epidermis, dichotomous branched, very fugacious, black; conidia ovoid, solitary. C. oleaginum Cast. Mycelium circinate, fugacious, black; conidia sessile, ovoid, yellow-green. It forms blotches on olive leaves and on peduncles of the fruit. PLANT DISEASE FUNGI 399 Cladosporium Link (p. 398) Hyphse decumbent, intricately-branched, olivaceous; conidia globose to ovoid, greenish. In part = Mycosphserella. See p. 171. Some one hundred seventy-five species, many of them of eco- nomic importance. C. herbarum (Pers.) Lk. on many hosts = Mycosphserella tu- lasnei. See p. 175. C. citri Mas.i Fio. 368. — Cycloconium ole- aginum. After Boyer. FiQ. 369. — Cladosporium cu- cumerinum, mycelium, a hy- phal knot, conidiophore and spoers. After Humphrey. The fungus that causes scab on lemons, sour oranges, satsumas and pomelos, usually referred to under this name, does not belong to this genus, but apparently does belong to the Dematiacese- Amerosporae. C. herbarum (Pers.) Lk. var. citricolum Fawcett causes scaly 1 Winston, J. R. Citrus scab: its cause and control. U. S. Dept. Agr. Bull. 1118, 1923. 400 PLANT DISEASE FUNGI bark of Citrus. The fungus was grown in pure culture and inocu- lations were made resulting in from forty to sixty days in typical spots. C. cucumerinum E. & A. Effused, maculose, in mass grayish-brown, changing to dark olivaceous, forming spots on fruits; conidiophores cespitose, sparingly septate, simple, denticulate, pale; conidia ovoid, lemon- shaped or fusoid; olivaceous, 10-13 x 3-4 ix. It causes watery spots on cucumber leaves, also decayed spots in fruit. C. carpophilum Thiim. Spots orbicular, often confluent, blackish-green, forming circles; conidiophores erect, simple, sinuous, septate; conidia ovate, obtuse, continuous or 1-sep- tate, 10-12 X 4-6 m- Widely distributed causing scab of peach, plum, nectarine, apricot, cherry. ^ ^,^ „ In the twig the fungus breaks the cuticle from Fig. 370. — C. car- Y ^ ' ^ ^ pophiium. After the layers below and its hyphse project through cracks. Upon the leaf it causes shot holes. C. fulvum Cke. Conidiophores densely crowded rupturing the cuticle, sparingly branched, septate, nodulose, bearing a few conidia near the apex; Fig. 371. — C. fulvum. After Southworth. conidia elliptic-oblong, 1-septate, translucent, tawny, 10-20 x 4-6 /x. The hyphse are abundant on the lower sides of tomato leaves, forming a mold, varying from whitish to purplish in color. C. macrocarpum Preu. Subeffuse, black; conidiophores subfasciculate, simple, some- PLANT DISEASE FUNGI 401 what flexuose, brown; conidia oblong, or oblong-ovate, 2 to several septate, obtuse, pale l^rown. On spinach leaves causing disease. Others are on grape, cranberry, sweet potato, tomato, cucumber, corn, rice, pea, peony, Oncidium, oak, sycamore, poplar, walnut, beech, elm. Polythrincium Kunze & Schmidt (p. 398) Conidiophores erect, fasciculate, regularly flexuose or torulose, black, simple; conidia acrogenous, obovoid. P. trifolii Kze. on clover has been said to be the conidial stage of Phyllachora trifolii. Fusicladium Bonorden (p. 398) Conidiophores short, erect, straight, spar- ingly septate, subfasciculate, olivaceous; conidia ovoid or subclavate, continuous or 1-septate, ,., -1 r- J Fig. 372.— P. trifolii. Af- acrogenous, solitary or paired. terCorda. In part=Venturia and Phyllachora. Over forty species, several pathogenic. F. fraxini Aderh. on Ash. = V. fraxini. F. saliciperdum (All. & Pub.) Lind. on Salix=V. chlorospora. F. cerasi (Rab.) Sacc. on cherry, peach, = V. cerasi. F. pirinum (Lib.) Fcl. on pear=V. pirina. See p. 182. F. dendriticum (Wal.) Fcl. on pomaceous fruits=V. insequalis. See p. 182. F. orbiculatum Thtim on Sorbus= V. inaequalis var. cinerascens. F. depressum (B. & Br.) Sacc. on Umbenifer8e= Phyllachora. F. betulae Aderh. on birch=V. ditricha. F. tremulae Fr. on aspen= V. tremulse. F. destruens Pk. Conidiophores short, 20-50 //, fasciculate, continuous or 1 to 2-septate, basally, colored, clusters slightly olive-green; conidia acrogenous, continuous or 1-septate, subcatenulate, ellipsoid to oblong, colored, 7-20 x 5-7 fx. On oats. , F. effusum Wint. Spots minute, rounded, rarely effused, confluent, smoky; conid- iophores erect, simple or slightly branched, septate, torulose, brownish, lighter above, 100-140 x 4 /u; conidia oblong fusoid to 402 PLANT DISEASE FUNGI rhomboid, continuous or uniseptate, light fuscous, subtruncate, 17-24 X 5.5-7 At. It constitutes the pecan scab, affecting the leaves, stems and nuts. Others are on buckwheat, flax, Eriobotrys. Scolecotrichum Kunze & Schmidt (p. 398) Conidiophores short, subfasciculate, olive; conidia oblong or ovate, pleurogenous or acrogenous. A genus of some thirty species very similar to Fusicladium. S. graminis Fcl. Spots foliicolous, elongate, ochraceous; co- nidiophores densely fasciculate, filiform, sim- ple, sinuous, 90-100 x 6-8 /jl, subcontinuous; conidia fusoid-obclavate, 35-45 x 8-10 fx, uni- septate, olive-brown. It is common, causing leaf spots on grasses, especially on A vena and Phleum. The myce- lium collects below the stomata and pushes its Fig. 373.— S. graminis. tuft of hyphffi tlirOUgll them. After Saccardo. j~,. i t • i / Others are on ash, Ins, banana, oats. Dematiaceae-Phragmosporae Conidia 2 to many-celled, dark, rarely light or liyaline, ovoid to cylindric or vermicular. Key to Genera of Dematiaceae-lPhragmosporaB Fertile hyphae very short or little different from the conidia Conidia not in chains, muticate; straight ovoid to cylindric, solitary 1. Clasterosporium, p. 403. Fertile hyphae distinctly different from the conidia Conidia solitary or nearly so, acrog- enous for the most part Conidia echinulate 2. Heterosporium, p. 403. Conidia smooth Hyphse short, ascending or erect, conidia ovoid to oblong 3. Napicladium, p. 404. PLANT DISEASE FUNGI 403 IlyphiE longer, rigid; conidia elon- gate, 4. Helminthosporium, p. 40i. Conidia verticillate, pleurogenous; hyplise dark, not rostrate at apex. . 5. Spondylocladium, p. 407. Clasterosporium Schweinitz (p. 402) Hyphae creeping, here and there swollen, conidiophores erect, bearing 2 to several-septate, solitary, apical conidia. A genus of some seventy-five species. C. carpophilum (Lev.) Aderh. Aderhold by inoculations, properly controlled, showed this fungus capable of causing gum- mosis of prunaceous hosts. Effuse, hyphae simple or short-branched, densely aggregated, septate, conidia elongate-fusoid, obtuse, 4 to 5-septate, slightly constricted at the septa. It is commonly seen as the cause of a brown spot on peaches. Spores do not appear in the young spots but are found sparingly in older brown areas. C. amygdalearum (Pass.) Sacc. is also described on rosaceous hosts. It is perhaps identical with C. carpophilum and may be connected with Pleospora vulgaris. C. putrefaciens (Fcl.) Sacc. causes spots on leaves of the sugar- beet. Heterosporium Klotzsch (p. 402) Hyphae subcespitose, smoothish, often branched; conidia oblong, 2 to several-septate, smoothish to granular or echinulate. A genus of forty species or more. H. echinulatum (Berk.) Cke. Spots gregarious, on fuscous areas; conidiophores fasciculate from a stromatic base, 150-200 x S fx, rarely shorter, flexuose- nodose, fuliginous; conidia at the nodes, oblong-cylindric, rounded at the ends, 2 to 3-septate, 40-50 x 15-16 //, sHghtly constricted, roughened, brownish. It causes a destructive mold on carnation leaves and stems. H. variable Cke. Conidiophores flexuose, slender, more or less nodulose at the septa; conidia cylindric oblong, 2 to 4-septate, minutely warted, 20-25 X 7-10 fjL, pale olive. On spinach. Other parasitic species are on Liliaceae, larch, Auricula, lilac, hop, Iris, Narcissus and other Monocotyledons. 404 PLANT DISEASE FUNGI Napicladium von Thiimen (p. 402) Conidiophores short, subfasciculate, smoothish; conidia acroge- nous, solitary, large, oblong, 2 to many -sept ate, smoothish. A small genus. N. soraueri is a form of Venturia insequalis with somewhat atypical napiform spores. N. janseanum Rac. is on rice. Helminthosporium Link (p. 403) Conidiophores erect, rigid, subsimple, fuscous; conidia fusoid to elongate-clavate or cylindric, pluriseptate, fuscous, smooth. In part=Pleospora. See p. 188. About two hundred-fifty species; several are important patho- gens, others saprophytes. The species show biologic differentiation into races similar to that exhibited in the Erysiphacese, though morphologically they may be inseparable. Saltation ^ has also been shown to occur commonly in the genus and definite determination of species is extremely difficult. The conidial forms named below have been considered responsible for diseases on the hosts mentioned in connection with them. H. gramineum Rab. on grasses =Pleospora gramineum. See p. 189. On barley it causes the leaf -stripe disease. The conidiospores have been shown to be long-lived and spring infection begins largely from conidia carried over winter on the seed. The mycehum invades the tissue causing long brown spots. These later bear conidiophores. Ravn regards the. disease pro- duced by H. gramineum as often general, not local, in that the mycelium invades the embryonic tissue of the growing points, resulting in infection of all the leaves. H. trichostoma=Pleospora trichostoma. See p. 189. H. teres Sacc. On barley causing net blotch. Spots oblong. The hyphae, according to Ravn, penetrate the outer cell wall of the epidermis then branch abundantly and may fill the cell 1 Stevens, F. L. The Helminthosporium foot-rot of wheat, with observations on the morphology of Helminthosporium and on the occurrence of saltation in the genus. 111. Nat. Hist. Surv. Bulletin, 14: Art. 5, 77, 1922. PLANT DISEASE FUNGI 405 completely; they then proceed into the intercellular spaces of the mesophyll and thereafter remain intercellular. H. avenae-sativse (B. & Cav.) Lind. On oats causing leaf spots. FiQ. 374. — Helminthosporium gramineum. Conidiophores and spores. After King. The conidia of the last two species infect grains and seedlings. The conidia spread the disease from the early infection centers to other parts of the plants but the mycelium remains local. Fig. 375. — Helminthosporium teres. Conidiophores and spores. After King. H. bromi Died, on Bromus=Pleospora bromi, see p. 189, H. tritici-repentis Died. = Pleospora tritici-repentis, see p. 189. H. sativum Pamm., King & Bakke 406 PLANT DISEASE FUNGI The cause of a destructive late blight, spot blotch, of barley. The disease manifests itself by dark colored, elongate spots on Fig. 376. — Showing variation in conidial shape and septation of H. No. 1, also the dark spot, stipe, at basal end, and the pale apical spot. After Stevens. the leaves. It also occurs on the glumes and spikelets, sometimes even penetrating the grains. A member of the H. sativum group is the cause of rotting of the basal part of the stems of wheat (foot rot) also of rye. The particular strain (Stevens H. No. 1) causing this rot of wheat is characterized by a conidium with a very short, 2 X 4 ju, black stipe at the base (Fig. 376) and with a pale spot at the apex. The conidia are from 4 to 10-septate, (mode 8), their length 34-99 ju, (mode 78 m) their thickness 17-24 /^ (mode 20 /x)- Infection is directly through the cuticle, not sto- matal, and the mycelium is intercellular within the host. H. sorokinianum Sacc. is reported on wheat and rye. H. turcicum Pass. Spots, large, dry, brownish; conidiophores, gregarious to fascicu- Fio. 377. — H. No. 1, showing variation in conidio- phores, geniculation, conidia-scars, and septation. After Stevens. PLANT DISEASE FUNGI 407 late, septate, 150-180 x 6-9 m, pale olive, apex almost hyaline, often nodulose; conidia spindle-shaped, acute, 5 to 8-septate, pale olive, 80-140 x 20-26 m- It produces spots on corn and sorghum. H. inconspicuum C. & E. Conidiophores elongate, septate, nodose, pale brown; conidia lanceolate, 3 to 5-septate, 80- 120 X 20 M, smooth. On corn and oats. H. inaequalis Shear Sterile hyphse effuse, much branched, dark brown; conidiophores erect, septate, variable in length, 6-8 m in diameter; conidia both terminal and lateral, more or less curved, 3 to 5-celled, fig. 378.— Heimintho thick-walled, brown, 23-32 x 11-14 jjl. On cran- berry. sporium insequalis. After Shear. Spondylocladium Martins (p. 403) The genus is characterized by its dark, multiseptate conidiophores, which bear the many-celled conidia pleuro- genously in the form of whorls. S. atrovirens Harz ^ The conidia are formed first either at the apex or the distal end of the intermediate cells. The lowest whorls of the conidia are borne about halfway between the base and the apex of the conidiophores, and the conidia are at- tached at the broad end. They vary in length from 18-64 fx, in breadth from 6-12 fi, and are 4 to 8-septate. It is the cause of potato silver-scurf. The fungus enters the tuber through the lenticels or directly through the epidermis and is limited to the corky Fig. 379. — S. atrovirens, a conidio- -, ■... . ■, •• . cc p ii"^ phore and conidia from mycelium layer, rCSUltmg m SlOUghmg Oil 01 the LaXrt'*' ""• ^''" ''''''"' '"^ corky and epidermal layers. 1 Schultz, Eugene S. Silver-scurf of the Irish potato caused by Spondylocladium atrovirens. Jour. Agr. Res. 6: 339, 1916. 408 PLANT DISEASE FUNGI Dematiaceae-Dictyosporae Conidia dark, rarely light muriform, globose to oblong. Key to Genera of Dematiaceae-Dictyosporae Hyph« very short or scarcely different from the conidia I. Micronemeae. Conidia not in chains, not appendaged, irregularly muriform or sarciniform, without conic points, ovoid to ob- long, loose 1. Sporodesmium, p. . 408 Hyphse distinctly different from the conidia II. Macronemeae. Conidia uniform Conidia not in chains or capitate Conidia single HyphsB alike; conidia muriform, typically smooth Hyphae decumbent 2. Stemphylium, p. 408. Hyphae erect or ascending Conidia ovoid to oblong, acrogenous ; conidio- phores somewhat lax, colored 3. Macrosporium, p. 409. Conidia catenulate; hyphae velvety, erect, subsimple; conidia caudate. . 4. Alternaria, p. 410. Sporodesmium Link Mycelium and eonidiophores poorly de- veloped; conidia ovoid oblong, subsessile or short-stalked, rather large, clathrate- septate, fuligineus. S. piriforme Cda. on oranges =Pleospora hesperidearum. S. exitiosum Kuhn on crucifers=Lepto- sphaeria napi. Others are on potato, cucumber, salsify, egg-plant, asparagus, beet. Stemphylium Walroth Conidiophores decumbent, intricately branched, hyaline or smoky; conidia acro- genous, ovoid to subglobose, 2 to many- FiQ. 380. — Sporodesmium anti- t „ „i •. r T •„ ,, quum. After Saccardo. muritorm-septate, fuligmous. PLANT DISEASE FUNGI 409 S. cucurbitearum Osner ^ Sporophores arise singly on the lower surface of the leaf, hyaline to light brown, 1 to 5-septate, 10-30 x 7-12 fx, the individual cells becoming globose and easily broken apart, bearing a single spore at the apex; the spores are nearly globose, dark brown, muriform, 25-50 )U in diameter, composed of 5-20 cells each of which is 10-18 m in diameter, easily breaking away from the sporophores. On leaves, stems, and petioles of gourds, cucumber and squash causing leaf spots. S. citri Pat. & Charles Vegetative mycelium long, hyaline, becoming dark, 4 ^ in diameter, septate; conidiophores short; conidia dark brown, subglobose to ob- long, apiculate, irregularly muriform, 20-30 x 12-15 fjL, usually in chains of three. This is found associated with an end-rot of oranges and is perhaps the cause of the disease. S. tritici Pat. Hyphae irregularly branched; conidiophores closely septate, 4-5 ju in diameter; conidia catenulate, irregular, usually clavate, constricted slightly at the septa, 24-35 x 12-15 /x, vermiculate, fuliginous, isthmus short, 3-4 ju in diameter. It is described as the cause of floret sterility of wheat. Fig. 381. — Stemphj' lium. After Saccardo. Macrosporium Fries (p. 409) Conidiophores fasciculate, erect or not, more or less branched, colored ; conidia usually apical, not catenulate, elongate or globose, dark-colored. In part=Pleospora. See p. 188. Macrosporium is distinguished from Alternaria by its solitary spores, not catenulate. Elliott ^ believed catenulation in these forms to be correlated with an attenuated apex, therefore that all beaked spores of the Alternaria-Macrosporium type, under suitable conditions, would produce chains. Applying this distinc- ^ Osner, George A. Stemphylium leaf spot of cucumbers. Jour. Agr. Res. 13: 295, 1918. ^ Elliott, J. A. Taxonomic characters of the genera Alternaria and Macrosporium. Am. Jour. Bot. 4: 439, 1917. 410 PLANT DISEASE FUNGI tion most of the forms previously reported as Macrosporium would be regarded as Alternarias. M. commune Rab. = M. sarcinula parasiticum Thlim. on vari- ous grasses =Pleospora herbarum. It is reported as the common black mold which follows Perono- spora on the onion and which occurs often also on onions not so diseased, being especially common on the seed stalks. It is usually associated with injured plants and may be important only as a wound parasite. M. porri E., M. alliorum C. & M. and M. sarcinula Berk, are also on onion. Others are reported as causing disease on cantaloupe, grape, pepper, rice, turnip, horseradish, cabbage, collards, and other crucifers, celery, tobacco, red clover, cotton, lettuce, iris, Chieran- thus, violet, Saponaria, geranium, catalpa, hackberry. Alternaria Nees. (p. 408) Conidiophores fasciculate, erect, subsimple, short; conidia clavate-lageniform, septate, muriform, catenulate. In part=Pleospora. See p. 188. A. sp. on Tropoeolum=Pleospora tropceoli. A. trichostoma Died, on barley =Pleospora trichostoma. See p. 189. A. brassicae (Berk.) Sacc. Conidiophores short, continuous, short-branched, apically equal; conidia elongate, fusoid, clavate, 60-80 x 14-18 /i, 6 to 8- muriform-septate, olivaceous. On crucifers generally. A. brassicae (Berk.) Sacc. var. nigrescens Pure cultures have been obtained and successful inoculations made on normal uninjured melon leaves. It is also reported as the probable cause of muskmelon leaf spots. A. violffi G. & D. Conidiophores erect, pale-olive, septate, simple, 25-30 x 4 /jl; conidia in chains at or near the apex of the conidiophore, clavately flask-shaped, strongly constricted at the septa, olive, 40-60 x 10-17 M. Circular leaf spots are produced on violets. Spores are found on the spots only when conditions are most favorable, i. e., in a humid air. The parasitism of the fungus was demonstrated by inoculation with spores on living leaves in distilled water. PLANT DISEASE FUNGI 411 A. citri Pierce ^ is held to be responsible for the abscissions result- ing in the June drop of Navel oranges also of a black rot of the fruits. Fig. 382. — A. violse, germinating spores. After Dorsett. A. dianthi S. & H. Spots epiphyllous, ashen- white, definite, circular, Conidiophores Fig. 383. — A. dianthi. 3, Mycelium showing branching and septation. 4, Showing myceUum below stoma and hyphse emerging through the stoma. 5, Showing catenulate spores as borne upon hyphse. 6 , Spores showing shape, septation and catenulation. 7, A young cluster of hyphse. 8, An older cluster of hyphse. After Stevens and Hall. cespitose from stomata, amphigenous, dark-brown, 1 to 4-septate, erect, 1-25 from a stoma; conidia 26-123 x 10-20 m, clavate, 1 Coit, J. Eliot and Hodgson, Robert W. An investigation of the Abnormal Shed- ding of Young Fruits of the Washington Navel Orange. Univ. of Cal. Pub. Agr. Sci. 3: 283, 1919. 412 PLANT DISEASE FUNGI tapering, obtuse, basally dark-brown, slightly constricted at the septa, 5 to 9 times cross-septate and 0-5 times longitudinally septate. It causes injury on carnation leaves and stems. A. solani (E. & M.) Jones & Grout Spots brown, circular to elliptic, concentrically zonate, amphige- nous, irregularly scattered over the leaf surface; mj^celium, light- brown; conidiophores erect, septate, 50-90 x 8-9 /*) conidia ob- Fiu. 384.— A. solani, spores germinating and penetrating the living potato leaf. After Jones. clavate, brown, 145-370 x 16-18 n with 5 to 10 transverse septa, longitudinal septa few, conidia terminating in a very long, hyaUne, septate beak half the length of the conidium or longer. It causes early blight, a leaf spot disease of potatoes and toma- toes. Its pathogenicity was proved by inoculations on tomato and potato, the spots appeared in eight to ten days after inoculation on vigorous uninjured leaves. The mycelium grows luxuriantly within the leaf but spores do not usually form until after the death of the supporting tissues when the conidiophores emerge PLANT DISEASE FUNGI 413 through the stomata or by rupturing the epidermis. Often no spores are formed and rarely are many present. The mycehum may live a year or more and resume sporulation the following sea- son. A. fasciculata (C. & E.) Jones & Grout Conidiophores light or dark-brown, becoming almost black, darker than the vegetative hyphse, but like them echinulate, 30-40 X 4-5 /x; conidia concolorous with the conidiophores, 35-66 X 16-20 [X, obclavate, 3 to 6 times cross-septate, 1 to 2 longitudinal septa, apical cell hyaline. This fungus is associated as a saprophyte with the blossom-end- rot of tomatoes and also causes a serious decay of the ripened fruit. The literature of the disease is rather voluminous and con- tains a number of sjmonyms, among them Macrosporium tomato, M. lycopersici, M. rugosa, M. fasciculata. A. mail Roberts enlarges dead spots of apple leaves; another species causes core rot. Others are on Forsythia, carrot, tobacco, ginseng, fig, grape, olive. Dematiacese-Scolecosporae Conidia dark or subhyaline, vermiform or filamentous, multi- septate. There is only one genus. Cercospora Fries. Conidiophores variable, almost obsolete or well developed, simple or branched; conidia vermiform or filiform, straight or curved, multiseptate, subhyaline to dark. In part=Mycosph8erella. See p. 171. The genus is a very large one, some seven hundred species, and contains very many aggressive, important parasites, chiefly causing leaf spotting. The spots are often blanched and are rendered ashen colored in the centers by the presence of the dark hyphse. The hyphse are usually geniculate at the point of spore production. Fig. 388, and thus old hyphse bear traces of spores previously borne. C. cerasella Sacc. on cherries = My cosphaerella cerasella. See p. 172. C. gossypina Cke. on cotton = Mycosphserella gossypina. See p. 176. 414 PLANT DISEASE FUNGI C. circumscissa Sacc. Spots amphigenous, circular, pallid, dry, deciduous; conidio- phores fasciculate, nodulose, brownish, simple; conidia acicular, narrowed apically, attenuate, tinged brown, 50 x 3.5-4 ^. On various species of Prunus this causes leaf holes. It is reported as especially serious on the almond. C. angulata Wint. Spots roundish, angulate, whitish to cinereous, margined, 1-3 mm. in diameter, often confluent; conidiophores hypophyllous, fasciculate, erect, straight or only slightly flexuose, simple, brownish, few-septate, 78-105 X 5 jjl; conidia filiform-obclavate, long at- tenuate, hyaline, 7 to 16-septate, 80-170 x 3.5 ix. On the currant. C. concors (Casp.) Sacc. Spots amphigenous, pale above, whitish be- neath, rounded, indefinite; conidiophores fascicu- late or single from the stomata, erect, brown, septate, simple, 40-80 /x high; conidia single, api- cally variable in form, ovate to elongate, curved, 1 to 5-septate, subhyaline, 15-90 x 4-6 /x. Conidia are abundant on the spots, on potato Fio. 385.— c. con- leavcs, ou stalks emerging from the stomata. The cors.Hyphse . ^ . f. . , , ,.„„ ., ii' emerging through superior and mierior nyphse diner considerably in fng^aiSTut^'a E' length and branching. Brown beadlike chlamyd- Pomeroy°°*'^ ^°^ ospores form within the leaf. The mycelium is strictly intercellular. Inoculations result in dis- ease spots in about three weeks after spraying with suspensions of spores. C. nicotianae E. & E. Spots amphigenous, pale, becoming white, with a narrow and inconspicuous reddish bor- der, 2-5 mm. in diameter, conidiophores am- phigenous, tufted, brown, septate, 2 or 3-times geniculate above, simple or sparingly branched, septate, 75-100 x 4-5 /x; conidia slender, slightly ^^°- ^^^fj curved, multiseptate, 40-75 x 3-3.5 /jl, hyaline. On tobacco it causes leaf spots. The sporiferous hyphse are abundant near the center of the disease spots. C. apii Fr. Spots amphigenous, subcircular, pale-l)rown, 4-6 mm. in diame- ■C. nirotianae. After Sturgis. PLANT DISEASE FUNGI 415 ter, with a more or less definite elevated margin ; conidiophores hypophyllous, light- brown, fasciculate, continuous or 1 or 2- septate, subundulate, 40-60 X 4-5 At; conidia hyaline, obclavate or almost cylindric, 3 to 10-septate, slender, 50-80 X 4 ju. Fig. 388.— C. apii. After Dug- gar and Bailey. Fig. 387. — C. nicotiansR, spores germinating and entering stomata. After Sturgis. A serious leaf spot is produced on celery, parsnips, etc. C. beticola Sacc. Spots amphigenous, brownish, purple- bordered, becoming ashy centered; conid- iophores fasciculate, short, simple, erect, flavous, 35-55 x 4-5 m; conidia elongate, filiform obclavate, hyaline, multiseptate, 75-200 X 3.5-4 /x. This fungus causes a very serious dis- ease of beet, producing spots on the leaves. Found also on spinach. The conidiophores usually, though not always, emerge from the stomata from a few-celled stroma and are amphigenous. They vary in length and septation with age. If in humid atmosphere the spots become hoar}^, due to the large number of spores present. Each cell of the spore is capable of germination. The germ tubes infest the host through the stomata. Pure cultures of the fungus may readily be secured by the usual methods. Here the mycelium produces dense matted colonies of deep olive color and a greenish-gray aerial growth but no conidia. 416 PLANT DISEASE FUNGI C. fusca Rand. = Calsterosporium diffusum Heald and Wolf. Leaf spots up to 10 or 15 mm. in diameter, at first somewhat angular and bounded by the veins, becoming roundish to irregular, dark reddish brown on both leaf surfaces; mycelium dark brown and septate, intercellular, sometimes also creeping over the leaf surfaces; conidiophores mostly epiphyllous, short and erect, typically in dense, tawny clusters from stromata, developed be- neath the epidermis and later bursting through, also arising singly from the prostrate surface mycelium; conidia pale olive brown, highly variable in size, 30-100 m or more by 3-6 m, usually curved, typically subclavate, multicellular. On pecan leaves. C. cucurbitae E. & E. Spots amphigenous, rounded, subochraceous, becoming thin and white, 1 to 4 mm. in diameter, border slightly raised; conidio- phores tufted, olive-brown, 70-80 x 4 /x, continuous, subgeniculate above, apically obtuse; conidia linear clavate, 100-120 x 3-4 /x, hyaline, septate. On cucumbers, associated with Phyllosticta cucurbitacearum. Others are on apple, fig, grape, Rubus, Citrus, coffee, spinach, egg-plant, watermelon, okra, pepper, horseradish, peanut, castor bean, cowpea, bean, clover, asparagus, water lily, violet, hollyhock, rose, phlox, oleander, Tecoma, orchids, geranium, mignonette, Odon- toglossum, lily, calla, mulberry, ash, butternut, catalpa, linden, maple, pecan, redbud, sequoia, willow. Stilbaceae (p. 377) Sterile hyphse creeping, scanty; fertile hypha? ,, „„ ^ ., , , collected into a stalk-like or stroma-like fas- l IG. 389. — Fertile hyphse . ■, -, • • t i j i j i and spores of c. beti- ciclc, bearmg couidia at the top, more rarely uggar. g^iQj^g ^i^Q sides, pale, bright-colored or dark. Hyalostibeae-Amerosporae Bright or light-colored, conidia globose, eliptic or oblong, con- tinuous. PLANT DISEASE FUNGI 417 Key to Genera of Hyalostibeae-Amerosporae Conidial part distinctly capitate or at least terminal Conidia not in chains; head of conidia not gaping or splitting above, not spiny; conidiophores of head normal; conidia covered with mucus; synema mono- cephalous; conidiophores not dendroid- verticillate 1. Stilbella, p. 417. Conidia in chains; synema with conidia above, not pubescent; conidia without mucus 2. Coremium, p. 417. Stilbella Lindau Hyphse forming a coremium which is capitate above; conidio- phores borne on the cap; conidia small, often enclosed in sHme. Over one hundred species chiefly saprophytes. (Commonly known as Stilbum, but the type of that genus being a hymeno- mycete it was renamed.) S. populi on poplar =Mycosph8erella popuU. Other species do serious injury to coffee and tea. Coremium Link Coremium cylindric, apically enlarged and fertile; conidia very small, catenulate. A small genus. In part=Rosellinia and Penicillium. See p. 163 and p. 125. Phaeostilbeae-Phragmo- sporae Conidia 3 to several-celled, oblong to c^dindric, dark or hyaline. Isariopsis Fries Slender, dark or subhyaline, cylindric hyphae laxly aggre- gated; conidia in a lax panicle or head, cylindric or clavate. See Fig. 391. Fig. 390. — Core- mium glaucum. After Corda. Fig. 391. — Isariopsis. After Saccardo. 418 PLANT DISEASE FUNGI I. griseola Sacc. Spots hypophyllous, ochraceous; coremium stipitate, dense. 200 X 30-40 n, composed of filiform hyphse; conidia borne on the reflexed ends of the hyphse, cyUndric-fusoid, curved, 50-60 X 7-8 M» graj^, 1 to 3-septate, constricted. It causes disease of beans. Tuberculariacese (p. 377) Hyphse compacted into a globose, discoid or verruciform body, the sporodochium ; sporodochia typically sessile, waxy or subgelat- inous, white, bright-colored or dark to black. In part=Nectria, Claviceps and Hymenoscypha, etc. See pp. 109, 148, 151. Tuberculariaceae-Mucedineae-Amerosporae Conidia hyaline or bright-colored, continuous, globose to f usoid ; hyphse hyaline. Key to Genera of Tuberculariaceae-Mucedineae-AmerosporeaB Sporodochia smooth or nearly so; conidia muticate Conidia not covered with mucus Conidia not acrogenous-capitate ; spo- rodochium without a heterog- enous cup; conidia not catenu- late or scarcely so, arising on out- side of hyphae; conidiophores present Conidia pleurogenous or acropleu- rogenous, ovoid to oblong 1. Tubercularia, p. 419. Conidia acrogenous; conidiophores not verrucose, not uredinico- lous; sporodochia verruciform or effuse; conidiophores simple, not united or radiate 2. Sphacelia, p. 420. Conidia covered with mucus; sporodo- chia verruciform or subeffuse 3. Illosporium, p. 420. Sporodochia ciliate at the margin; sporo- phores distinct; conidia not in chains; conidiophores not ciliate or united. ... 4. Volutella, p. 420. PLANT DISEASE FUNGI 419 Tubercularia Tode (p. 418) Sporodochium tubercular or wartlike, sessile or subsessile, smooth, rarely with bristles, usually reddish; conidiophores very slender, usually branched; conidia apical, ovate to elongate. In part =Nectria. See p. 148. Over one hundred species, chiefly saprophytes. Fig. 392. — Hyphae of Tubercularia, bearing conidia. After Durand. Fig. 393. — T. fici, sporodochium, showing setae and conidial formation. After Edgerton. T. vulgaris Tode = Nectria cinnabarina. See p. 148. T. fici Edg. Sporodochia scattered or gregarious, superficial or subcuticular, light pink, variable in size up to 3-4 x 1-1.5 mm., smooth, irregular in outline; conidiophores crowded, hyaHne, 20-27 x 1-2 ix; conidia small, clear, elliptic to oval, regular in size, 5-7 x 2.5-5 /x; setae scattered or abundant, variously placed, straight or curved, hyaline or subhyaline, septate, papillose, 60-90 x 4-6 ix. It is the cause of a fig canker. 420 PLANT DISEASE FUNGI Sphacelia Levielle (p. 418) Sporodochia planose, effuse, stromate or sclerotioicl ; conidio- phores short, simple, filiform; conidia apical, ovate. A small genus, chiefly conidia of Claviceps and related genera. S. segetum Lev. = Claviceps purpurea. Seep. 151. Illosporiuin Martins (p. 418) Sporodochia wartlike, pulvinate or subeffuse, white or light- colored, subgelatinous or waxy; conidiophores variable; conidia globose, sigmoid, variable, embedded in mucous. There are some forty species. I. malifoliorum Shel. Spots suborbicular or coalescing and becoming irregular, brown or mottled with gray and with a small gray spot near the center, 5-15 mm. in diameter; sporodochia hypophyllous, minute, gelatinous, yellow-amber, becoming black, spherical, becoming discoid or irregular, 150-160 fx in diameter; conidiophores branched; conidia ob- long, 1-3.5 X 4 '■{3} M- It is said to be one of the common and destruc- FigT^^^^^Tii^po- tive causes of leaf spots of the apple often resulting AftTr'Saccardi^' ^^ nearly complete defoliation. In the centers of the leaf spots other spots bearing other species of fungi are often found, leading to the thought that perhaps the Illosporium in such cases results from secondary infection in the wounds made by the earlier fungus. The sporodochia are hy- pophyllous, often hidden by the normal pubescence of the leaf. Volutella Tode (p. 418) Sporodochia discoid, regular, margin ciliate, sessile or stipitate; conidiophores usually simple; conidia ovoid to oblong. Some seventy species. V. leucotricha Atk. Sporodochia convex-discoid, white to pale flesh-color; setse few, filiform, few-septate, subhyaline; conidiophores densely fasciculate, filiform; conidia oblong. On cuttings in greenhouses. V. fructus S. & H. Spots on the fruit, circular; sporodochia, numerous in concentric "" ,.,, M ^^ i «^^^^tt ■hi m 1 h 1 jl^^^^B ^^S ™ E 1 1 ^M 1 ^^^^' PLANT DISEASE FUNGI 421 circles, cubcuticular, erumpent, elevated 200-250 m, 150-400 /jl in diameter; mycelium black; setae distributed throughout the sporodochium, black, 0 to 3-septate, acute, smooth, 100-400 x 5- 8 fx; conidiophores elon- gate, hyaline, simple, 25- 35 X 3 At; conidia smooth, oblong-fusoid to falcate- fusoid, hyaline or sub- olivaceous, 17-23 X 2.5- 3.5 fjL. It is the cause of a dry Fig. 395.— v. fnictus. Sporodochia in section. After , J. 1 Stevens and Hall. rot 01 apples. V. lycopersici Pritchard and Porte ^ causes collar-rot of tomatoes, killing young plants by girdling the stem. Other species are on carnation and Bletia. Tuberculariaceae-Mucedineae-PhragmosporaB Hyphae hyaline; conidia 2 to several-septate, hyaline or bright- colored, fusoid to falcate, rarely short and simple. Fusarium Link ^ Conidia often of diverse types; the larger ones (macroconidia) wedge shaped, fusiform, falcate, or uncinate, more or less pointed toward or at apex; smaller conidia, microconidia, either of similar shape, though smaller in size and continuous, or with fewer septa, or of a distinct type, oblong, ovate, reniform, lanceolate, etc.; conidiophores simple to compoundly subverticillate, produced on loose mycelium or over a flat or tuberculate layer of pseudopar- enchjrma; conidia terminal, single or in small or large balls, in buttery layers, pseudopionnotes, in gelatinous layers, pionnotes, or in separate tubercular masses, sporodochia; microconidia in some cases catenulate; neither conidia nor mycelium ever gray or black but from hyaUne to various hues of blue, yellow, brown, purple, and red. Due to the fact that many of the Fusaria produce spores in sporodochia, wart-like bodies composed of conidiophores and masses of conidia, the genus is usually placed under the Tubercu- 1 Pritchard, F. J. and Porte, W. S. Collar-rot on Tomato. Jour. Agr. Res. 21: 179, 1921. 2 The manuscript regarding this genus was prepared by C. D. Sherbakoff. 422 PLANT DISEASE FUNGI hiriacecC. The forms that produce conidia over a gelatinous layer of mycelial growth were formerly placed in the same family but in the genus Pionnotes; the forms with very short conidiophores were referred to the genus Fusoma in the Moniliacese. Some have also been placed in the genera: Cephalosporium, Trichothecium, Arthrosporium, Sporotrichum, Spicaria. Fig. 396. — A-C, Section Martielia; A, F. soiaui; B, F. nuirtii; C, F. cceruleum; D-E-F, Section Elegans: D, F. redolens; E, F. oxy- sporum; F, F. orthoceras; G-H, Section Discolor: G, F. culmo- nim; H, F. sulphureum; 7-7, Section Gibbosum: 7, F. falcatum; J. F. scirpi; K, Section Roseum: F. avenaceum; L, Section Ventricosum: F. agrillaceum. All conidia drawn were from pure cultures on steamed plant stems. Redrawn after WoUenweber. The ascigerous connection is in part with Nectria, Neonectria, Neocosmospora, Gibberella, Calonectria, Hypomyces, and Sphaer- ostilbe. This is a large genus in which many species have been described. However, many of the descriptions are entirely inadequate, there- fore, many of the names are relegated to synonymy. Some of the species are destructive parasites, invading the ducts of plants and by stoppage of the water supply (Fig. 398), causing the class of disease known as ''wilts." Others induce rot, spotting, cankers, etc. Taken as a whole the genus is one of the most injurious with which plant pathology has to do. It seems probable that some of the forms that live normally as saprophytes in soil may encroach upon living roots of susceptible plants when these are available. Biologic specialization has been found, in that forms apparently morphologically indistinguishable PLANT DISEASE FUNGI 423 are frequently incapable of cross inoculation onto other than their usual hosts. Most Fusaria grow well in culture, and the species often show marked differences in growth on various media, particularly in the colors that are developed, however, some of the species deteriorate very rapidly when carried on common artificial media. As with the anthracnoses much study is here needed to throw light on the inter-relation of the various species and their hosts. Appel and Wollenweber ^ and later others have made extensive studies of many species to lay the ground for a monograph. At present it is accepted that in delineating species strictly standard culture conditions should be used and that the important char- FiG. 397. — A, F. batatatis, niicroconidia; B, F. batatatis, ehlamyd- ospores; C, F. batatatis, conidia; D, F. hyperoxysporum ; E. F, culmorum; F, F. radicicola; G, F. orthoceras var. triseptatum. Redrawn after Wollenweber. acters are: the mode of production of conidia and their form, especially shape of their bases, apices, degree and type of curvature (see Fig. 399) and septation; the color of the mycelium and spores; and the presence, or absence, and type of chlamydospores, scler- otia, and microconidia. The two following genera closely resemble Fusarium and are often mistaken for it: ^ Appel, O & Wollenweber, H. W. Grundlagen einer Monographie der Gattung Fusarium (Link). Arb. Kais. Biol. Anstalt f. Land u. Forst 8:1, 1910. Wollen- weber, H. W. Studies on the Fusarium problem. Phytop. 3: 24, 1913. 424 PLANT DISEASE FUNGI I. Ramularia (Unger) Fries. It differs from Fusarium primarily in that the conidia typically are not curved, nearly cylindric, with a more or less rounded apex and not pedicellate. Fusarium candidum Ehr. = Ramularia Candida (Ehr.) Woll. II. Cylindrocarpon Woll. differs from Fusarium in that the conidia are typically cylindric to subcylindric, with both ends rounded. Fusarium album Sacc. = Cylindrocarpon album (Sacc.) Woll. The following are a few of the Fusaria and Fusaria-like fungi which at present are con- sidered to be conidial forms of certain ascomy- cetes: ^ Fusarium fructigenum Fr. V. majus Woll. = Gib- berella juniperi (Desm.) Woll. Fusarium graminearum Schwabs = Gibberella saubinetii (Mont.) Sacc. Fusarium mali All. (= Cyl- indrocarpon) = Nectria galligena Bres. Fusarium minimum Fcl.= Calonectria graminicola (Berk. & Br.) Woll. Fusarium pallens (Nees.) Link = Sphserostilbe coccophila Tul. Fusarium pyrochroum (Desm.) Sacc. = Gibberella euonymi (Fcl.) Sacc. Fusarium salicis Fcl. = Gibberella effusa Rehm. Fusarium sphseri® Fcl. = Hypomyces leptosphserise (Niessl) Woll. Fusarium urticearum (Cda.) Sacc. = Gibberella moricola (Ces. & de Not.) Sacc. Fusarium willkommii Lind. (= Cylindrocarpon) = Nectria ditissima Tul. Cylindrocarpon ianthothele Woll. = Hypomyces rubi (Osterw.) Woll. Ramularia magnusiana (Sacc.) Lind. =Neonectria ramulariae Woll. 1 WoUenweber, H. W. Fusaria autographice delineata, Ann. Myc. 15:34, 1917. Fig. 398. F. vasinfectuni, showing thrombosis of veins. After Atkinson. PLANT DISEASE FUNGI 425 Key to Sections of Fusarium ^ Conidia in perennial, true pionnotes; aerial mycelium typically absent, slow growing fungi Section Eupionnotes. Conidia in pseudopionnotes, or in sporo- dochia, or in small balls, sometimes in chains, or single; aerial mycelium in cultures usually present Chlamydospores intercalary to none Quasi Fusaria, i. e., possessing micro- conidia of conspicuously different types than those of true Fusaria Microconidia pyriform Section Sporotrichiella. Microconidia lanceolate, 0 to 3-sep- tate Section Arthrosporiella. Microconidia in chains Macroconidia thick-walled, mostly 6 and more septate Section Specarioides. Macroconidia thin-walled, mostly 3 to 5-septate Section Moniliforme. True Fusaria; sporodochia convex, macroconidia pedicellate, micro- conidia rare; sometimes blue sclerotia present Conidia typically narrow, not no- ticeably broader in diameter near the middle Conidia gradually attenuated Section Roseum, p. 431. Conidia pinched near apex Conidia with thin walls Section Laterium. Conidia with more or less thick walls Conidia uniform, chlamydo- spores common Section Discolor, p. 430. Conidia more or less variable, no chlamydospores Section Saubinetii. Conidia mostly noticeably wider in diameter near the middle; not pinched near apex. Chlamydospores present Section Gibbosum,p. 431. ^ The first key to sections covering a considerable number of the species was given by C. D. Sherbakoff, Fusaria of Potatoes, Cornell Univ. Agr. Exp. Sta. Mem. No. 6, 1915. Another key covering a wider range of the species was pub- lished by WoUenweber, "Conspectus analyticus Fusarium," Berichten d. deut. Bot. Ges. Jahrg. 1917, 35, H. 10: 732-739. 426 PLANT DISEASE FUNGI Chlamydospores terminal and inter- calary; frequently plectenchymic substrata and also dark colored sclerotia occur Conidial walls and septa thin ; macro- conidia pointed toward apex. . . Section Elegans, p. 427. Conidia thick-walled, with thick septa Conidia at apex obtuse to ob- liquely subrounded, no ascig- erous stage known Section Martiella, p. 429. Conidia at apex sometimes pointed, conidial stage of Hypomyces Section Pseudomartiella. Chlamydospores terminal; no pion- notes, no tubercular sporodochia; growth floccous; conidia subcur- vate, apex slightly attenuate, apedicellate Section Ventricosum, p. 432. Section Moniliforme Microconidia continuous, oval to short spindle-shaped, single or in chains, balls, pseudopionnotes, and sporodochia; macroconidia single or in pseudopionnotes and sporodochia, in some species rare, in others abundant, usually slightly curved toward apex, with very thin walls and septa, slightly pinched at apex, usually pedicellate ; mostly 3-septate and measure 25-40 x 2.5-4.5 fx; some 4 and 5- septate; aerial mycelium mostly hyaline to grayish or bluish purple, well-developed to very scant; substratum on glucose agars color- less to dark grayish or bluish purple ; no chlamydospores ; in cer- tain species production of minute, blue sclerotia like bodies, probably immature perithecia of a Gibberella, are common on certain media, steamed sweet potato plugs, etc. Fusaria of this section superficially much resemble those of section Elegans; however, they are of a distinct group in having no true chlamyd- ospores, in microconidia borne in chains and of a short spindle- shape; in the shape of macroconidia; and in undoubted connection with some Gibberella species, probably G. acervalis (Moug.) Woll. A species of this section, F. moniliforme Sheldon, was recorded as causing mold of corn ears, first in Nebraska and now in prac- tically every other state. The same species, or one closely related to it, was found to cause damping off of coniferous seedlings in the United States. PLANT DISEASE FUNGI 427 Section Elegans All species have microconidia, mostly unicellular, scattered or in balls, ellipsoidal or reniform, averaging 5-12 x 2-3.5 /x; sickle-shaped conidia, macroconidia, (Fig. 396, D, E, F) mostly 3-septate, usually 25-40 x 3-4.5 n, but also 4 and 5-septate, usually 40-50 X 3-4.5 II. Sporodochia, with or without a sclerotial base, are common; pseudopionnotes also often present. Conidia in masses mostly salmon-colored, sometimes brownish white or bril- liant orange. Conidiophores single to compoundly subverticellate. Chlamydospores ellipsoidal to round, terminal and intercalary, mostly unicellular and measuring 5-10 n. Ascigerous stage un- known. Many of the forms in this group are vascular parasites though sometimes causing parenchyma rot. Distinctive characters of better known species of economic importance are given in the following annotated key. Key to Species of Section Elegans No sporodochia. pseudopionnotes, or sclerotia; macroconidia few. Sub- section Orthocera. Mycelium 3^ellowish F. citrinum Woll. On decaying tomato fruit Mycelium not yellowish Rice cultures wine-red. F. orthoceras App. & Woll. In Irish potato roots and tubers and in tomato stems. Fig. 397 G Rice cultures not wine-red. F. conglutinans Woll. Vascular para- site of cabbage and aster Sporodochia typically present. Subsection Oxysporum. Sclerotia blue. Series Cyanostroina. Macroconidia considerably curved. F. tracheiphilum, E. F. Sm. 3-septate conidia 25-35 x 3.25-4 /x; 4 and 5-septate rare. Vas- cular parasite of cowpeas. Macroconidia moderately curved Macroconidia comparatively narrow, nearlj^ cylindric through greater part of their length; F. batatatis Woll. (Figs. 397, A- C) ; occasionally found to cause wilt (stem rot) of sweet pota- toes; F. bulbigenum Cke. & Mass., morphologically appears to be the same as the preceding species; of the same type and size of macroconidia, 3-septate, 25-50 x 2.75-3.75 m; 4 and 5- septate, 30-50 x 3-4 /x; on rotted bulbs of narcissus, decaying tubers of Irish potatoes and on apples Macroconidia comparatively broad and wider about the middle Macroconidia in numerous, small sporodochia 428 PLANT DISEASE FUNGI 3-septatc conidia 35 x 4.3 (30-40 x 4.0-4.6) m; 4 and 5-septate common, averaging 40 x 4.4 fx; blue sclerotia large (on steamed potato tuber plugs) ; F. sclerotioides Sherb. In vascular systems of Irish potato and corn stems. 3-septate conidia 30 x 4.3 (25-35 x 3.5-4.5) /jl; 4 and 5-septate conidia rare; blue sclerotia small; F, blasticola Rostrup. In vascular system of potato tubers and on pine seedlings. Macroconidia in few, large sporodochia; pionnotes (pseudo) not conspicuous, not continuous. 3-septate conidia up to 100%, 30 x 4 (25-40 x 3.25-4.5) m; 4 and 5-septate very rare to none; F. oxysporum Schlecht. Vascular parasite causing wilt of Irish potatoes, also found on tomatoes, cowpeas, peas and sweet potatoes. F. malli Taub., the cause of onion pink root, is not closely related to F. oxysporum, but much resembles F. solani. 3-septate conidia 30-50 x 3-4.25 Ai; 4 and 5-septate com- mon; F. niveum E. F. Sm. Vascular parasite causing wilt of watermelons. 3-septate conidia about 60-80%, 35 x 4.25 (30-40 x 3.5-4.5) Ijl; 4 and 5-septate 20 to 40%, 5-septate 43 x 4.25 (40-45 x 4-4.5) ju,; F. auranticum (Link) Sacc. In living stems of Irish potatoes, decaying cucurbits, corn, Lagenaria and Rubus. Macroconidia inconspicuous, continuous pionnotes (pseudo) Macroconidia somewhat narrow, mostly 3-septate, 27-28 x 3- 3.75 m; 4 and 5-septate few; F. vasinfectum Atk. Vas- cular parasite producing wilt of cotton and okra. Macroconidia somewhat broad, 4 and 5-septate common; 3- septate 34 x 4.1 (25-45 x 3.5-4.25) /jl; F. hyperoxysporum Woll. (Fig. 397, D) ( = F. lutulatum Sherb.) . Causes stem rot of sweet potatoes; also rot of Irish potato tubers. Sclerotia pale to none. Series Pallens. Conidia slightly broader near the middle septum; not pinched at apex Sporodochia poorly developed; mycelium tremelloid-effuse, readily decumbent, plectenchymatic sclerotia ochrous. F. • euoxy- sporum Woll. 3-septate conidia 35 x 3.5 (30-42 x 3-4.5) fJL; 4 and 5-septate rare. Found in vascular system of potato tubers, and also causing potato tuber rot. Sporodochia numerous, often confluent Growth on agars in plate distinctly zonate. 3-septate conidia averaging 33 x 4.2 ju; 4 and 5-septate conidia few, 5-septate 39-4.6 M- F. zonatum (Sherb.) Woll. On rotted potato tubers PLANT DISEASE FUNGI 429 Growth on agar in plates not zonate, macroconidia often in pionnotes (pseudo); 3-septate conidia up to 100%, 30-40 X 3.3-3.5 At. F. lycopersici Sacc. Vascular parasite caus- ing wilt of tomatoes Conidia broader at the upper third septum, somewhat pinched near apex Pionnotes present. 3-septate conidia 36 x 4.8 (31-41 x 4.3-5) /z; 4 and 5-septate not many. Chlamydospores when 0-septate about 8.5 X 9 IJL.F. reddens Woll. Causes stem rot of Pisum sativum (Germany), found also on rotted potato tubers (New York). No pionnotes; sporodochia sometimes numerous, medium to large; 3-septate conidia 35 x 5.25 (27-43 x 4.8-6.3) /u,; 4-septate rare, no 5-septate; chlamydospores, when 0-septate, 11 (6-18) fi. F. spinaciae Sherb. Causes root rot of spinach. Section Martiella The species have conidia of the form shown in Fig. 396, A, B, C. Chalmydospores present. No ascus stages known. Fusarium coenileum (Lib.) Sacc. (Fig. 396, C). Conidia normally triseptate, averaging 30-40 x 4.5-5.5 /x, seldom 4 and 5-septate. Conidial mass brownish white and yellow ochre to reddish ochre. Plectenchymatic stroma chiefly violet to indigo-blue and bluish black; by infiltration with the latter color the conidial mass may become bluish green as in other species of the section Martiella. F. coeruleum is the only species of this section having reddish ochre conidial masses. Chlamydospores as in other species of the section. Cause of potato tuber rot. F. martii App. & Woll. (Fig. 396, B). Conidia mostly non-septate, single, or in pseudopionnotes and sporodochia and then mostly 3 and 4-septate; 3-septate 44 x 5.15, 30-51 x 4.9-5.3 /x, 4-septate 49 X 5.3 (48-50 x 4.9-5.4) /jl, 5-septate from rare to 7 per cent; color of conidial mass deep lichen to green and dark blue. Sapro- phyte, at least does not cause potato tuber rot, bean dry rot, or stem rot of garden peas. F. martii phaseoli Burkh. morphologically is about the same as F. martii but differs from it by causing dry root rot of several different beans of the genus Phaseolus, of black-eye cowpea (Vigna sinensis) and of kulti bean (Dolichos biflorus). F. solani (Mart. p. par.) App. & Woll. (Fig. 396 A). Microco- nidia always present, at least on aerial mycelium; macroconidia often slightly broader in their upper half, typically 3-septate, 30 x 5.5, 25-35 X 5.4-5.8 /z, 4-septate from few to 5 per cent, 5-septate 430 PLANT DISEASE FUNGI from none to 0.5 per cent. Very common saprophyte on potato tubers and other substrata; cause of a gray rot of economic aroicls. F. eumartii Carp. Macroconidia in their protoplasmic appear- ance often are strikingly similar to F. coeruleum; mostly 4 to 6- septate, 54-75 x 5.5-6.6 /x; conidial masses in exposed pseudopion- notes brownish white to bright brown and, through absorption of the color from substratum, becoming gray and blue-gray; aerial mycelium weakly developed; chlamydospores 7-10 fx. It causes potato tuber and stem rot. F. radicicola Woll. Conidia normally 3-septate (Fig. 397, F), less often 4 or 5-septate, scattered or in sporodochia or pionnotes / Fig. 399. — Spores of Fusarium showing curvature in different species. F. sp., F. cceruleum, F. culmorum. After Appel and WoUenweber. averaging 30-45 x 3.75-4.5 fx. Chlamydospores 7-10 /jl. On partly decayed tubers and roots of plants, particularly on white potato and sweet potato. Cause of the jelly end rot and lenticel dry rot of potato tuber and rot of potato stem. Section Discolor Conidia of the form type shown in Figure 396 G, H. Interca- lated chlamydospores present. Ascigerous stage unknown. F. culmorum (W. G. Sm.) Sacc. (Figs. 396, G, 397, E). = F. rubiginosum App. & Woll. This differs from the conidial stage of Gibberella saubinetii PLANT DISEASE FUNGI 431 sharply in type of conidia and in the presence of clusters and chains of intercalated chlamydospores and it has no connection with the ascus stage. Conidia scattered in sporodochia or in pionnotes, in masses ochraceous to salmon colored, 5-septate, averaging 30-45 x 5.5-7 fx, seldom 3 to 4-septate, rarely with a larger or smaller number of septa. The slight constriction at the apical end and the pedicel- late base of normal conidia makes this fungus a type species of the section Discolor. Chlamydospores intercalated, single, in chains or in clusters, averaging 7-14 fj, in diameter. Common on partly decayed plants. It is a wound parasite on cereals and causes root rot. It has been found on the following hosts: Zea, Triticum, Hordeum, Solanum, Cucurbita. F. trichothecioides Woll. In contrast to the other species of the section Discolor this forms two sorts of conidia: (1) The comma type, formed as a slightly curved comma rounded at both ends; and (2) the normal macroconidia, typical of the section. It is a wound parasite, the cause of dry rot of potato tubers. Section Gibbosum Conidia of the form shown in Figure 396, I, J. Intercalated chlamydospores. Ascigerous stage unknown. F. falcatum App. & Woll. (Fig. 396, I) Conidia 5-septate, 35-55 x 4-5 ijl, parabolically curved. A wound parasite, cause of tomato fruit rot. F. scirpi Lamb. & Fautr. (Fig. 396, J.) (=F. gibbosum App. & Woll.) Conidia 5 (5-7) septate, 30-60 x 4-5.2 /x, hyperboUcally curved. Probably a cause of potato tuber rot. F. sclerotium Woll. This differs from F. scirpi in having spherical, blue sclerotia. Conidia mostly 5-septate. A wound parasite, the cause of fruit rot on tomato and watermelon. Section Roseum Conidia of the form-type shown in Figure 396 K. No true chlamydospores but as a rule sclerotia, blue in a number of species. Ascigerous stage unknown. F. avenaceum (Fr.) Sacc. (=F. subulatum App. & Woll.) Fig. 396, K, N. Saprophytic on various dead substances; a wound parasite 432 PLANT DISEASE FUNGI only under conditions of high humidity and closed air; sometimes causes scab and seedling bUght of cereals and dry rot of potato tubers. Section Ventricosum Conidia of the form-type shown in Figure 396, L. No sporo- dochia. Chlamydospores terminal only. Ascigerous stage un- known. F. agrillaceum (Fr.) Sacc. (Fig. 396, L). = F. ventricosum App. & Woll. Conidia never formed in sporodochia, brownish-white to cream colored, 3-septate, 29-37 x 5.75-7.5 fx. Conidiophores bostryx-like or irregularly branched. Chlamydospores terminal only. Wound parasite, cause of a tuber rot of potato. Several species that have not yet been critically studied nor assigned to places in the sections given above are said to be the cause of a disease. They are given below. F. rubi Wint.=Ramularia rubi (Wint.) Woll. Mycelium white, becoming pink, especially abundant on the flowers; conidia elongate, 1 to 8-septate, variable in size and form, straight or curved, 14-30 x 3-3.5 m, not constricted. Cook found this fungus in diseased buds of dew- berries and by inoculation demonstrated that it is Fia 400— F rubi responsible for witches' broom, doublc-blossom, and section of ovar>' similar abnormal growths of this plant. showing myce- _ , . -r» p r-i ium between F. miZOgenum F. & C carpel and ovule. ri ^ ^ ' i2'i-ij^r» 'ii After Cook. Sporodochia superficial, 1 to 2 mm. wide, dense, convex, white or whitish, hyphse densely inter- woven, septate, subramose; conidia oblong, roundish, 1-septate, 70x4/x. It was originally described as a parasite on apple roots in Ne- braska. The mycelium grows within the roots and gummosis of the wood occurs. Microconidia are known, also chlamydospores. F. cubense E. F. Sm. was isolated from bananas affected with blight. Inoculation showed the fungus capable of growing through the bundles for long distances. F. limonis Bri. Sporodochia gregarious, confluent, white; hyphse spreading, branched, septate; conidiophores erect, with alternate or opposite branches; conidia variable, acrogenous, continuous to 3-septate, PLANT DISEASE FUNGI 433 Fig. 401.— F. lini. After Bolley. oblong to fusiform, curved, pointed, slightly constricted, 26-27 x 2.4-2.8 M. This fungus is held to be contributory to, if not responsible for, the Mal-di-gomma or foot rot of citrous fruits which is known practically wherever these fruits are cultivated. F. lini Boll. Sporodochia erumpent, compact, cream to flesh- colored ; conidiophores short, much branched; conidia 3-septate, fusiform, slightly curved to falcate, 27-38 X 3-3.5 /x. A serious, widespread flax wilt is caused. The mycelium develops luxuri- antly from bits of diseased stem laid in sterile Petri dishes and grows well in culture media. Normally a soil saproph3rfce, it invades the roots, grows through the veins, plugs the ducts and causes death. The sporodochia are found abundantly on the bases of diseased plants. The spores abound on all diseased parts particularly on the seeds. Infection experiments have dem- onstrated its patho- genicity. F. violse Wolf Infected areas dark, sunken ; sporodochia Fig. 402. — F. lini, sketch, showing the mode of attack upon TTtrifUiri +Vio Vir»af • nr\ a young root tip of a seedUng flax plant. After Bolley. WlUlllli bue llObl, LO- nidia fusiform-falcate, 28-38 X 4-6 fjL, 3 to 5-times septate; hyphse hyaline, 4-7 fx in diameter, irregularly branched. It causes a disease of roots and stems of pansy. Others are on fig, celery, pea, tobacco, corn, alfalfa, carnation, chrysanthemum, Colocasia, sweet pea, onion, ricinus, cacao, Pelargonium, cabbage, rice, etc. 434 PLANT DISEASE FUNGI Tuberculariaceae-Dematieae-Phragmosporae Hyphse dark; conidia usuall}^ colored, 2 to several-septate, ob- long; to cylindric. Key to Genera of Tuberculariaceae-Dematieae-Phragmosporae Conidiaiii chains; sporodochium discoid. . 1. Trimmotostroma, p. 434. Conidia not in chains, muticate; sporo- dochium smooth; conidia not pro- liferate and united; sporodochia con- vex-pulvinate 2. Exosporium, p. 434. Trimmotostroma Corda Sporodochia pulvinate, compact, bearing a layer of conidio- phores; conidia oblong, often curved, 2 to 8-septate, catenulate, brown. A genus of a half dozen species. T. abietina Doh. Mycelium perennial; sporodochia foliicolous or caulicolus, diffuse; conidiophores subhyaline or tinged with olive-brown, 4.5 X 20-30 fx, septate, sparsely branched, bearing the conidia terminally; conidia catenulate, very variable, dark olivaceous- brown, slightly roughened, usually oblong, spherical, straight or inequilateral, continuous, 5 /x, or 2 to 5-celled and 5-6 x 8-16 fx, not constricted, rarely muriform, 5 x 10 )u. On white and balsam firs. The perennial habit of the mycelium makes the pest a persistent one and as no conidia are produced till the second year after infection its presence is the more readily overlooked. Exosporium Link Sporodochia convex, compact; conidiophores dark, simple, densely compacted; conidia single, oblong to cylindric, plurisep- tate. Some twenty -five species. In part =Coleroa and Coryneum. E. juniperinum (E.) Jacz. = Coryneum juniperinum. E. laricinum Mas. is found on larch. E. tiliae Lk. grows on linden. E. palmivorum Sacc. on palms. PLANT DISEASE FUNGI 435 Fig, 403. — E. palmivorum, 3, a sporodochium, 5, spores. After Treleasc. Mycelia-Sterilia (p. 334) Numerous forms are known merely as sterile mycelia. They may or may not make sclerotia. In several instances these sterile forms are so aggressive as to warrant classing them among the worst of plant pathogens. Until more is known of them it becomes necessary to arrange and name them, for convenience of reference, in a purely artificial manner. Key to Form Genera of Mycelia-Sterilia. Tubercle-like Tubercles connected with fibrils 1. Rhizoctonia, p. 435. Tubercles without fibrils; cortex not dis- crete 2. Sclerotium, p. 438. Cobwebby or byssoid, cespitose interwoven, primary hyphse joined in bundles 3. Ozonium, p. 440. Rhizoctonia De CandoUe Sclerotia variable in form, horny-fleshy; cortex thin, membranous, persistent, inseparable; formed among and connected by the mycelial threads. There are about a dozen so-called species, some of them very important plant pathogens. The two most important species of Rhizoctonia may be dis- tinguished by the following characters: R. crocorum appears as an external felt, pink to violet, protoplast violet, and infection 436 PLANT DISEASE FUNGI cushions present; R. solani has myceKum only as a web, yellow to yellow-brown, protoplast hyaline, no infection cushions. R. solani Kiihn =Corticum vagum (see p. 290), as does also part of what has been referred to as R. violacese. R. crocorum (Pers.) DC.^ -=R. medicaginis DC.= R. violacea Tul. The younger external hyphse are almost colorless. As the hyphse grow older the walls of the cells become a brownish violet which gradually deepens until the older hyphal strands are a decided violet to buff color. The young hyphal tips measure Fio. 404. — R. crocorum: cells characteristic of the tufted growth covering the surfaces of the large sclerotia and to a certain extent of the "infection cushions." After Duggar. 12-14 ix in diameter, while the older hyphse measure 7.2-10 /x. The long conductive vegetative cells vary in length from 55- 173 /i. The cells covering the superficial sclerotia are, as a rule, shorter, 30-50 ix, and thicker, 12-14 /x, than the cells of the con- ductive hyphse. The internal mycelium strands are septate and branched, the direction of the branching here being determined by the cells of the hosts. Within the superficial mantle of mycelium on the surface of the stem there soon appear reddish-black sclerotial ^ Faris, James A. Violet root rot (Rhizoctonia crocorum DC.) in the United States. Phytop. 11: 412, 1921. 2 Duggar, B. M. Rhizoctonia crocorum (Pers.) DC. and R. Solani Kiihn (Corti- cium vagum B. & C.) With notes on other species. Ann. Mo. Bot. Card. 2: 403, 1915. PLANT DISEASE FUNGI 437 bodies. They vary from the size of a pin head to several centi- meters in length, and show cells considerably branched and curi- ously lobed and with all varieties of color from transparent to violet. On badly infected tubers large numbers of small specks the size of a pin head, infection cushions, are to be seen; from the tops of these many hyphse extend over the surface of the potato and young hyphal branches penetrate from them directly through the wall of a host cell and once inside branch profusely. Typical sclerotial cells are formed in the host cell until finally the cell is completely filled by the fungus. The host cells in infected tissue are disorganized until eventually several cells are broken down and Fig. 405. — R. crocorum : a, extreme forms of cells isolated from a macerated sclerotium. After Duggar. the cavities filled with a fungous mass. The infection cushions have their beginning in the cork cambium from the hyphal strands which have forced their way into the host tissue. Completely submerged sclerotia are not uncommon. On potato, alfalfa, asparagus, carrot, beet, causing root rot; also on some 54 species in 22 families ranging from Pinaceae to Compositae. When abundant the fungus completely invests the root with a weft or mat of hyphse, at first buff to violet, later red- violet to violet-brown. On Alfalfa practically all attacked plants lose their tap roots. In heavily affected plants the cortex of the roots easily slips away from the vascular cylinder. On the potato, plants show yellowing and wilting of the lower leaves which soon drop. The entire under part of the stem is covered with mycelium. Occasionally 438 PLANT DISEASE FUNGI brown specks appeared in the epidermis of the stems and the roots; these consisting of dead surface cells of meristematic tissue, the injury not extending to the deeper layers of the cortex. R. microsclerotia Matz. Sclerotia superficial, small, 0.2-0.5 mm. in diameter, white when young, brown to dark brown at maturity, nearly homogenous in structure and color, subglobose, free from tufted mycelium, not smooth, usually single, sometimes conglomerated; vegetative hyphse 6-8 fj, wide, at first hyaline and granular, brown and more or less empty with maturity. On living leaves, branches and fruit of the cultivated fig. Others are on saffron, pine trees, coffee, buckwheat. Sclerotium Tode (p. 435) Sclerotia roundish or irregular in form, cartilaginous-fleshy, not connected by mycelial threads; cortex thin, membranous, in- separable. Over 200 species have been described. Fig, 406. — S. rolfsii, sclerotia. After Halsted. S. rolfsii Sacc. Sclerotia small, brown, about the size of a mustard seed. This sterile fungus possesses a very aggressive mycelium which under favorable conditions of moisture grows on almost anything PLANT DISEASE FUNGI 439 living or dead, producing a dense white cottonlike mass of threads. Soon the sclerotia form as mustard-seed-like bodies. They are produced in great abundance on all media but neither these struc- tures nor the mycelium have yet been seen to bear spores of any kind. The fungus was first studied by Halsted. It was de- scribed and named by Saccardo from specimens communicated Fig. 407. — S. rolfsii, sterile mycelium growing on carrot. After Stevens and Hall. by Stevens. Varietal strains occur as is shown by physiological and morphological differences in cultures. S. bataticola Taub. Sclerotia jet black, very minute; exterior smooth, made up of anastomosed, black hyphae; interior light to dark brown, of free, thick-walled cells; sclerotia spherical, oval, oblong, elliptical, curved or even forked, varying in size from 25 x 22-152 x 32 ^, abundant throughout the entire root of the host. Parasitic on living roots of sweet potato, causing black rot. 440 PLANT DISEASE FUNGI S. oryzae Catt. Sclerotia black, Vio nini- in diameter, glistening, arising from a slender white mycelium. The cause of injury to rice plants. S. rhizodes Awd. Subglobose, at first white, villose, then smooth, black, rugose. On wheat, also on Calamagrostis and other grasses. Other species are on tulips, onions and other bulbs. Ozonium Link (p. 435) Cobwebby or byssoid, cespitose, hyphae densely interwoven, primary hyphae fasciculate. Some twelve species. O. omnivorum Sh.i Mycelium dirt}^ yellow, sometimes whitish when young, grow- ing in the vascular bundles of the host; hyphae forming strands and spreading from them, producing a rather dense arachnoid layer on the surface of the host and bearing 1 to 4 branches arising and growing at right angles from the same point near the ends, 3 to 5 M in diameter, tapering toward the ends. It causes root rot on almost any kind of plant including among its hosts a large variety of trees. The fungus destroys the smaller rootlets, cortex of older roots and invades the vascular system and medullary rays, resulting in wilt and death. It may be seen superficially as dirty yellowish strands or as a thin weft. Sclerotia- like bodies appear on the roots often at lenticels. Inside of the host tissue the mycelium is not typically associated to form strands and its cells are hyaline. ^ Duggar believes the conidial stage to be a Phymatotrichum. INDEX (Boldface figures refer to headings) Abutilon, 390 Acanthorhynchus, 158 vaccinii, 158, 159 Acanthostigma, 159, 161 parasiticum, 161 Acer, 142 Acer villus, 52, 332 Aconitum, 77 Acrocystis, 7 Acrostalagmus, 389, 390 albus, 390 caulophagus, 391 Actinidia, 136 Actinomyces, 14, 48, 50 scabies, 48 Actinomycetacese, 14, 48 Actinomycetales, 14, 48 Actinonema rosea, 145 Adonis, 133 ^cia, 231 iEcidium, 231, 278 asperifolium, 273 berberidis, 240, 270 brassicae, 279 gossypii, 279 oxalidis, 275 punctatum, 256 rhamni, 274 rubellum, 269 iEciospores, 232 iEsculus, 137, 150 iEthalia, 8 Agaricacese, 286, 318 key to tribes of, 318 Agaricales, 282 key to families of, 286 Agaricese, 318 320 Agaricus, 282 Agave, 70, 176, 371 Agropyron, 21, 216, 229, 274 rep ens, 358 Agrostis, 229 Albuginacese, 63, 70 Albugo, 70, 71 bliti, 71, 72, 73 Candida, 71, 80 ipomoeae-panduranse, 73 occidentalis, 73 oospores of, 72 portulacese, 73 tragopogonis, 73 Alder, 150, 298, 306, 361, 368, 377 389 Alfalfa, 30, 39, 61, 81, 108, 110, 113, 151, 178, 186, 268, 291, 340, 351, 354, 359, 367, 368, 370, 389, 433, 437 Allium, 225, 248 Almond, 39, 256, 368, 414 Alnus, 96, 140, 142, 199, 366 Alternaria, 188, 408, 410 brassicse, 410 brassicse var. nigrescens, 410 citri, 411 dianthi, 411 f asciculata, 413 mali, 413 solani, 412 trichostoma, 189, 410 violse, 410, 411 Alyssum, 133 Amanita, 283 Amaranthus, 73 441 442 INDEX Amelanchier, 138, 262, 264, 265 Amentacese, 96 Amerosporae, 333 Amerosporium, 363 oeconomicum, 363 Ampelopsis, 136 Amphispore8, 232, 234 Anacardiacea), 97 Andromeda, 288 Anemone, 133, 256 Antheridium, 53, 56, 90 Anthiirium, 340, 368, 371 Antirrhinum, 105, 278, 340 Aplanobacter, 14, 18 stewarti, 18 Apothecium, 52, 87 Apple, 32, 39, 69, 86, 102, 112, 138, 139, 149, 164, 174, 176, 180, 182, 185, 190, 192, 199, 207, 236, 261, 263, 264, 265, 289, 291, 292, 293, 294, 298, 300, 306, 308, 309, 323, 326, 328, 338, 339, 340, 342, 344, 349, 356, 362, 366, 368, 376, 379, 382, 392, 413, 416, 420, 421, 427, 432 Apricot, 33, 256, 340, 400 Aquilegia, 133 Aralia, 124 Arbor- vita?, 116, 150, 302, 308 Arbutus, 39 Armillaria, 322, 326 mellea, 326, 327 mucida, 327 Arnica, 132 Aroids, 430 Aronia, 262, 264 Arrhenatherum elatius, 136 Arrowroot, 192 Arthrosporium, 422 Artichoke, 395 Asclepias, 142 Ascocarp, 87, 88 Ascochyta, 171, 350 ablemoschi, 350 chrysanthemi, 351 Ascochyta fragariae, 351 — — gossypii, 350 graminicola, 186 hortorum, 343 lathri, 176 lycopersici, 351 medicaginis, 351 piniperda, 351 ■^ pisi, 176 Ascogenous hyphae, 91 Ascogonium, 129 Ascoma, 87 Ascomycetes, 55, 87 — — key to subclasses, 91 Ascospora, 165 beyerinckii, 165, 375 Ascus, 87 Ash, 150, 270, 298, 311, 340, 351, 359, 368, 373, 401, 402, 416 Asparagus, 43, 269, 346, 408, 416, 437 Aspen, 183, 306, 320, 401 Aspergillacese, 123 key to genera of, 123 Aspergillales, 94, 122 Aspergilleae, 378, 380 key to genera of, 380 Aspergillus, 123, 124, 380 ficuum, 380 niger, 380 phoenicis, 380 Aspidistra, 371 Aster, 135, 243, 427 Asteroma, 196, 336, 346 • padi, 346 Astragalus, 141 Atriplex, 62 Atrocarpus, 366 Auricula, 403 Auricularias, 281 Autcecious, 232, 235 Avena, 17, 135, 271, 402 Avocado, 192, 353 Azalea, 359 INDEX 443 B BacillacesB, 15 Bacillus, 14, 15, 40 ■ — — amylovorous, 17, 40 aroidese, 44 atrosepticus, 17, 41, 42 avenae, 23, 41 carotovorus, 17, 42, 43, 44, 45 coli, 44 lathyri, 44 melonis, 44 morulans, 44 mus2e, 17, 44 nicotianse, 36 oleracesB, 44 ■ — - — omnivorus, 44 phytophthorus, 17, 41, 45 solanacearum, 35 — — solanisaprus, 41, 45 tracheiphilus, 17, 46, 47 Bacteria, 2, 9 classification of, 13 Bacteriacese, 14, 18 Bacterial disease in plants, types of, 15 Bacterium, 14, 15, 18, 21 agropyri, 21 exitiosum, 28 maculicolum, 17 michiganense, 17, 20 rathayi, 17, 21 sojse, 28 solanacearum, 35 — — stewarti, 17, 18 stizolobii, 17, 21 teutlium, 17, 21 Balsam, 177, 300, 313 Bamboo, 220 Banana, 44, 366, 402, 432 Barberry, 239, 368 Barley, 27, 37, 86, 135, 186, 188, 189, 214, 216, 217, 220, 271, 275, 358, 369, 393, 398, 404, 406, 410 Basidia, 53 Basidiomycetcs, 56, 210 key to the subclasses, 211 Basidiospore, 52, 233 Basidium, 52, 56, 210 Bean, 15, 27, 32, 36, 39, 67, 86, 93, 105, 124, 176, 193, 202, 291, 339, 342, 369, 386, 416, 418, 429 Beech, 150, 177, 294, 298, 306, 308, 311, 313, 317, 327, 367, 368, 401 Beet, 21, 23, 39, 42, 44, 47, 48, 62, 73, 175, 186, 230, 270, 339, 340, 351, 357, 395, 408, 415, 437 Begonia, 124, 368 Berberis, 142, 236, 271 Berchemia, 275 Beta, 268 Betula, 96, 140, 142 Betulacese, 108 Biologic specialization, 238 Birch, 149, 150, 181, 183, 292, 296, 298, 304, 306, 308, 310, 311, 313, 315, 320, 368, 377, 401 Blackberry, 41, 199, 258 Black raspberry, 390 Blastotrichum, 148 Bletia, 421 Bluegrass, 23, 153, 276, 278, 346, 369 Boraginacese, 274 Botryosphseria, 204 berengeriana, 205 fuliginosa, 205 — — marconii, 205 — ribis, 204 Botrytideae, 378, 384 key to genera of, 384 Botrytis, 101, 106, 385 — alii, 389 cinerea, 386 • pseonise, 387 parasitica, 388 tulipse, 387, 388 Boudiera, 90 Box, 362 444 INDEX Box elder, 150, 188, 340, 367 Brassica, 133, 279 Bremia, 74, 79 lactucse, 80 Bridging hosts, 271 Bromus, 188, 189, 274, 405 inermis, 358 Brunchorstia destruens, 115 Buckwheat, 278, 394, 402, 438 Bulbs, 105, 440 Butternut, 199, 298, 306, 351, 367, 368, 373, 416 c Cabbage, 15, 25, 42, 72, 80, 106, 164, 176, 291, 337, 341, 351, 368, 410, 427, 433 Cacao, 199, 291, 371, 395, 433 Cactus, 39 Cffioma, 257, 278, 279 ■ nitens, 257 Calamagrostis, 440 Calendula, 132, 133, 134 Calla, 43, 47, 340, 375, 416 Calonectria, 147, 160, 422 graminicola, 150, 424 Calospheeria, 203 princeps, 203 Calospora, 365 vanillae, 366 Camellia, 144, 192, 346 Campanula, 245 Cankers, 15, 16 Canna, 278 Cantaloupe, 410 Caper, 72 Capillitium, 8 Capnodiaceae, 127, 144 Capnodium, 144 Caraway, 341 Carex, 268 Carnation, 39, 268, 291, 340, 346, 359, 368, 385, 389, 403, 412, 421, 433 Carpinus, 96, 142, 342, 368 Carrot, 28, 42, 77, 105, 188, 291, 341, 342, 413, 437, 439 Carya, 140, 149, 164, 192 Cassava, 344 Castanea, 104, 140, 142 Castilleja, 253 Castor bean, 416 Catalpa, 124, 133, 142, 184, 304, 340, 410, 416 Catenulate, 51 Cattleya, 366 Cauliflower, 25, 29, 80, 176 Cedar, 295, 297, 302, 308, 309 Celastrus, 142 Celery, 22, 28, 42, 105, 107, 339, 341, 357, 410, 415, 433 Cenangiacea), 100, 114 Cenangium, 115, 364 abietis, 115 piniphilum, 115 Centaurea, 134, 278 Cephalosporiese, 378, 379 Cephalosporium, 148, 379, 422 acremonium, 380 Cephalothecium, 391, 392 roseum, 392 Ceratostomatacese, 157, 164 Ceratostomella, 164 pilifera, 164 Cercis, 176 Cercospora, 171, 185, 413 angulata, 414 apii, 414, 415 beticola, 415 cerasella, 172, 413 circumscissa, 414 concors, 414 cucurbita;, 416 fusca, 416 gossypina, 176, 413 nicotianse, 414 Cercosporella, 395 persicae, 395 Cereals, 150, 151, 431, 432 Cereus, 362 INDEX 445 Chsetostroma, 148 Chalara paradoxa, 396 Chamaecyparis, 295 Chenopodiacese, 81 Chenopodium, 62 Cherry, 41, 47, 98, 138, 150, 156, 172, 183, 199, 203, 256, 298, 326, 351, 353, 359, 400, 401, 413 Chess, 369 Chestnut, 39, 181, 206, 298, 304, 316, 319, 337, 340, 348, 353, 359, 373, 374, 376 Chicory, 106, 188, 270, 278, 340 Chieranthus, 410 China aster, 390 Chinaberry, 79, 149, 150 Chinquapin, 304 Chlamydospores, 51, 89, 212, 213 Choanephoracese, 85, 86 Choanephora cucurbitarum, 87 Chrysanthemum, 39, 277, 340, 351, 359, 376, 379, 433 Chrysomyxa, 279 Chrysophlyctis endobioticum, 58 Chytridiales, 50, 56, 57 key to f amihes, 57 Cichorium, 134 Cicinnobolus, 130 Cineraria, 244 Citron, 194 Citrus, 70, 144, 177, 342, 343, 359, 370, 384, 389, 400, 416, 433 canker, 16 Cladochytriaceae, 57, 60 Cladosporium, 156, 185, 188, 398, 399 carpophilum, 400 citri, 399 cucumerinum, 400 fulvum, 400 herbarum, 175 var. citricolum, 399 macrocarpum, 400 Clamp connections, 211 Clasterosporium, 402, 403 amygdalearum, 403 Clasterosporium carpophilum, 403 — — diffusum, 416 • putrefaciens, 403 Claviceps, 147, 151, 418, 420 microcephala, 153 paspali, 153 purpurea, 151, 152, 420 rolfsii, 153 Cleistothecopsis, 142 — — circinans, 142 Clematis, 133, 134, 351, 368, 377 Chtocybe, 322, 327 monadelpha, 327 — ■ — parasitica, 327 Clover, 39, 62, 81, 108, 124, 151, 177, 178, 186, 267, 345, 366, 367, 370, 379, 389, 401, 410, 416 Coccacese, 14, 18 Coccomyces, 116, 117, 376 hiemalis, 117, 119 lutescens, 118 pini, 119 prunophorse, 117 Cocoanut, 44 Coenocytes, 51 Coffee, 177, 192, 291, 353, 355, 37L 395, 416, 417, 438 Coleosporiaceae, 241 Coleosporium, 241, 279, 280 campanulas, 244 ipomoese, 242 pini, 244 senecionis, 243, 244 solidaginis, 242, 243 Coleroa, 434 Collard, 25, 80, 410 Colletotrichum, 110, 190, 365, 369 althaea, 370 camelliae, 192 — — carica, 192 cereale, 369 erumpens, 370 falcatum, 369 gloeosporioides, 192, 370 gossypii, 195, 369 446 INDEX Colletotrichum lagenariiim, 194, 370 lindemuthianum, 193, 369 malvarum, 370 nigrum, 370 oligochsetum, 194 phomoides, 370 spinacise, 370 — — theobromicolum, 192 trifolii, 370 violse-tricoloris, 371 Collybia, 322, 328 — — • velutipes-, 329 Colocasia, 43, 70, S3, 433 Columbine, 105, 351 Colutea, 141 Comandra, 253 Composita), 73, 80, 134 Comptonia, 252 Conidia, 51 Conidiophore, 51, 332 Coniferse, 279 Conifers, 99, 109, 150, 161, 251, 291, 296, 297, 298, 300, 302, 304, 309, 313, 317, 323, 326, 353, 368, 375, .386 Coniofhyrium, 172, 185, 348, 349 — — - caryogenum, 349 diplodiella, 349 — fuckelii, 185, 349 — — megalospora, 160 pirinum, 349 tumefaciens, 349 Conjugate division, 237 Convallaria majalis, 344 Convolvulacea;, 73 Coremium, 163, 417 — — glaucum, 381 vulgare, 381 Coreopsis, 132 Corn, 15, 19, 47, 61, 75, 76, 151, 154, 218, 222, 236, 291, 352, 353, 380, 401, 407, 426, 428, 433 Cornus, 142 Corticium, 287, 288 Corticium koleroga, 289 la}tum, 291 — — salmonicolor, 291 • stevensii, 289 vagum, 290, 436 Corylus, 142, 368 americana, 373 Coryneum, 166, 374, 375, 434 beyerinckii, 165, 375 foliicolum, 375 juniperinum, 434 tumoricolum, 376 Cosmos, 36, 342 Cotoneaster, 262 Cotton, 15, 30, 39, 124, 176, 195, 205, 230, 279, 291, 342, 350, 353, 369, 390, 394, 410, 413, 428 Cottonwood, 313 Cowpea, 39, 124, 141, 339, 359, 363, 416, 427, 428, 429 Crab apple, 180 Cranberry, 104, 158, 192, 340, 345, 346, 359, 362, 364, 368, 375, 401, 407 Crataegus, 138, 142, 262, 263 oxycantha, 99 Crocus, 108 Cronartium, 246, 251, 279, 280 cerebrum, 253 comptonise, 252, 253 filamentosum, 253 — - — occidentale, 253 pyriforme, 253 quercus, 279 ribicola, 251 Crotalaria, 291 Crown gall, 38 Crucifers, 4, 15, 25, 42, 72, 80, 106, 341, 408, 410 Cryptosporella, 202 anomala, 202 viticola, 201, 202, 203, 346 Cucumber, 15, 29, 47, 78, 105, 106, 194, 340, 379, 400, 401, 408, 409, 416 INDEX 447 Cucumis, 133 Cucurbita, 133, 431 Cucurbits, 4, 15, 47, 78, 87, 124, 134, 135, 194, 340, 351, 357, 368, 428 Cuphea, 141 Currant, 77, 86, 111, 149, 204, 252, 310, 356, 414 Cuttings, 420 Cycad, 176 Cyclamen, 124, 192, 340, 342, 359, 371, 386 Cycloconium, 398 oleaginum, 398 Cydonia, 262 Cylindrocarpon, 424 album, 424 — — ianthothele, 424 Cylindrocladium, 391, 392 scoparium, 392 Cylindrosporium, 119, 171, 376 castanicolum, 376 chrysanthemi, 376 clematidis, 376 hiemalis, 117 juglandis, 377 lutescens, 1 18 mori, 360, 376 padi, 119, 376 pomi, 340 prunophorse, 118 ulmicolum, 377 Cyperus rotundas, 291 Cystospora, 3, 6 batatse, 6, 7 Cytology, 237 Cytospora, 200, 336, 348 chrysosperma, 348 rubescens, 199 D Dacryomycetes, 281, 282 Dactylium, 148 Dgedalea, 296, 316 quercina, 316 Dahlia, 36, 47, 133, 134, 342, 386, 389, 390 Daisy, 39 Daisy, Paris, 38 Damping off, 64 Dandelion, 270, 278, 395 Dasyscypha, 101, 108 resinaria, 109 willkommii, 108 Datura, 36 Daucus, 133 Deciduous trees, 294,. 298, 300, 304, 305, 308, 309, 311, 317, 323, 324, 326 Delphinium, 133 Dematiacese, 377, 396 AmerosporsB, 396 key to subfamilies of, 396 Dictyosporse, 408 key to genera of, 408 -Didymospora), 398 — — key to genera of, 398 ■ Phragmosporse, 402 key to genera of, 402 Scolecosporae, 413 Dematophora, 163 necatrix, 164 Dcndrophoma, 336, 344 convallarise, 344 marconii, 344 obscurans, 344 ■ valsispora, 344 Desmodium, 141, 142 Dewberries, 432 Dianthus, 268, 278 Diaporthe, 199, 200, 340, 346 ambigua, 340 ^batatis, 200 • phaseolarum, 202 sarmentella, 340 strumella, 347 taleola, 200 umbrina, 201 Dibotryon, 155 morbosum, 155, 156 448 INDEX Dictyosporse, 333 Didymaria perforans, 373 Didymellina, 184 iridis, 184 Didymosphaeria, 178, 184 catalpae, 184 Didymosporse, 333 Diervilla, 133 Diffuse, 10 Digitalis, 340, 351 Diospyros, 138 Diplocarpon, 145 rosea, 145, 146 Diplocladium, 148 Diplodia, 171, 352 gossypina, 353 longispora, 353 macrospora, 353 natalensis, 353 zeae, 352 Diplodina, 350, 351 citrullina, 174, 351 Dipsacus, 132, 133 Discomycetes, 89 Discula platani, 196 Distichlis, 270 Doassansia, 213, 222, 230 gossypii, 230 Dogwood, 150, 202, 293, 359 Dolichos, 266 biflorus, 429 Dothichiza, 363, 364 ■ caryae, 164 ferruginosa, 115 populea, 364 Dothideales, 95, 154 Dothiorella, 204, 336, 347 gregaria, 347 quercina, 347 ribis, 347 Double-blossom, 432 Douglass fir, 386 Downy mildew, 73 Dracana, 340, 346, 371 Drupaceous hosts, 15, 165, 292, 339 E Echinodontium, 293, 295 tinctorium, 295 Egg plant, 36, 291, 343, 351, 368, 389, 390, 408, 416 Elder, 140 Eleagnus, 275 Elm, 137, 149, 150, 181, 188, 198, 294, 298, 308, 325, 337, 340, 350, 360, 368, 373, 376, 377, 401 Elymus, 274 Emmer, 151, 369 Endive, 270, 278 Endoconidium, 110 Endomyces, 93 mali, 93 Endomycetacea), 92, 93 Endothia, 204, 205 parasitica, 206 Entomosporium, 171, 363 maculatum, 113, 363 mespili, 363 thumenii, 363 Entyloma, 213, 222, 229 crastophilum, 229 ellisii, 229 irregulare, 229 polysporum, 229 Enzymes, 2, 15, 43, 46, 64, 229, 301 Epithecium, 100 Ericacea), 108 Eriobotrys, 402 Erodium, 28 Erwinia, 15 amylovora, 40 carotovora, 42 lathy ri, 44 phytophthora, 45 tracheiphila, 47 Erysiphaceae, 127, 379 key to subfamilies and genera of, 131 Erysiphe, 91, 129, 131, 133 cichoracearum, 130, 134 INDEX 449 Erysiphe graminis, 135 liriodendri, 134 martii, 134 polygon!, 133 umbelliferarum, 134 Erysipheae, 131 Euascomycetes, 91, 94 key to orders of, 94 Eubacteriales, 14 Eubasidii, 211, 280 Eucalptus, 375 Eumycetes, 2, 50 key to classes, 55 Euphorbia, 141, 236, 237 gerardiana, 268 Eutaphrina, 96 Euthelephoraeese, key to genera of, 287 Excipulaceae, 335, 363 Hyalosporse, 363 key to genera of, 363 Exoascaceae, 95 Exoascus, 96 Exobasidium, 95, 287 vaccinii, 288 Exosporium, 434 juniperinum, 434 laricinum, 434 palmivorum, 434, 435 tiliae, 434 F Fabraea, 110, 112, 171, 363 maculata, 112, 113, 363 mespili, 363 Fagopyrum, 133 Fagus, 142 Favolus, 296, 315 europeeus, 315 Fern, 65, 96, 177 Festuca, 135, 220 Ficus, 199, 368, 371 elastica, 177 Fig, 21, 192, 291, 344, 380, 413, 416, 419, 433, 438 ' Filbert, 203 Fir, 99, 108, 150, 161, 162, 181, 202, 250, 294, 295, 296, 302, 304, 308, 309, 315, 340, 342, 344, 351, 375, 434 Fission, 10 Flagella, 10 Flax, 247, 433 Fomes, 296, 305 annosus, 308 applanatus, 313, 314 carneus, 308 everhartii, 308 fasciatus, 312 fomentarius, 307 fraxinophilus, 311 fulvus, 310 igniarius, 306 juniperinus, 309 laricis, 310 marmoratus, 312 nigricans, 311 pinicola, 312, 313 ribis, 310 robiniae, 311 sessilis, 312 Forget-me-not, 83 Form genera, 240 Forsythia, 413 Foxtail, 75 Fragaria, 132 Fraxinus, 142 Fruit, 315 Fuligo, 148 Fumago, 144 Fungi, classification of, 55 Fungi imperfecti, 331, 56 key to orders of, 334 Funkia, 340 Fusarium, 147, 148, 150, 151, 421 key to sections of, 425 agrillaceum, 422, 432 album, 424 450 INDEX Fiisarhnn arthrosporiella section, 425 aviranticum, 428 avenaceum, 422 batatatis, 423, 427 blasticola, 428 bulbigenum, 427 candidiim, 424 citriniim, 427 coeruleum, 422, 429, 430 conglutinans, 427 cubense, 432 culmorum, 422, 423, 430 cyanostroma, 427 discolor section, 425, 430 elegans section, 426, 427 key to species of, 427 eumartii, 430 euoxysporum, 428 eupionnotes section, 425 falcatum, 422, 431 ■ ■ fructigeniim, 424 — — gibbosiim section, 422, 425, 431 graminearum, 424 hyperoxysporiim, 423, 428 lateriiim section, 425 limonis, 432 lini, 433 liitulatum, 428 lycopersici, 429 mali, 424 malli, 428 martiella section, 420, 429 martii, 422, 429 — — phaseoli, 429 minimum, 424 moniliforme, 426 section, 425, 426 niveum, 428 orthocera subsection, 427 orthoceras, 422, 423, 427 var. triseptatum, 423 Fusarium, pallens, 424 — ■ — pallens series, 428 pseudomartiella section, 426 I)yrochroum, 424 radicicola, 423, 430 redolens, 429 rhizogenum, 422, 432 — - — roseum section, 425, 431 rubi, 432 — — rubiginosum, 430 salicis, 424 saubinetii section, 425 scirpi, 422, 431 sclerotioides, 428 sclerotium, 431 solani, 422, 428, 429 specariodes section, 425 sphaerisB, 424 spinacia), 429 sporotrichiella section, 425 — • — subulatum, 431 — — sulphureum, 422 tracheiphilum, 427 — — trichothecioides, 431 urticearum, 424 vasinfectum, 428 ventricosum, 432 section, 426, 432 oxysporum, 422, 428 subsection, 427 violae, 433 willkommii, 149, 424 zonatum, 428 Fusicladium, 398, 401 betula), 401 cerasi, 401 dendriticum, 182, 183, 401 depressum, 401 destruens, 401 effusum, 401 ■ fraxini, 401 orbiculatum, 401 • — — pirinum, 182, 401 saliciperdum, 401 tremulae, 401 Fusicoccum, 196, 203, 336, 346 putrefaciens, 346 INDEX 451 Fusicocciim veronense, 197, 346 viticolum, 346, 347 Fiisidium, 148 Fusoma, 422 G Gaillardia, 132 Gallowaya, 244 Gametes, 53 Garden pea, 291 Garlic, 81 Gasteromycetes, 282 Geranium, 28, 32, 386, 389, 395, 410, 416 Gibberella, 147, 150, 422, 426 acervalis, 426 effusa, 424 evonymi, 424 juniperi, 424 moricola, 424 saubinetii, 150, 151, 424, 431 Ginger, 65 Ginkgo, 192 Ginseng, 47, 69, 105, 107, 124, 346, 375, 390, 391, 395, 413 Gladiolus, 39, 177, 229, 359 Gleditsia, 192 Gloeodes, 145, 360 pomigena, 360 GlcEosporium, 110, 179, 190, 196, 365 ampelophagum, 366 apocryptum, 367 atrocarpi, 366 betularum, 367 caryse, 366 caulivorum, 367 cinctum, 366 — — cingulatum, 192, 366 — ■ — cylindrospermum, 366 fagi, 367 fructigenum, 192, 366 — '■ — juglandis, 367 la^ticolor, 366 — — macropus, 366 Gloeosporium malicorticis, 112 medicaginis, 367 musarum, 366 nervisequum, 196, 366 paradoxum, 366 piperatum, 194, 366 platani, 196 psidii, 366 ribicolum, 192, 366 ribis. 111, 366 rubi, 192, 366 rufomaculans, 192, 366 salicis, 366 trifolii, 366 ulmeum, 197 ulmicolum, 367 vanillae, 366 venetum, 125 versicolor, 366 Glomerella, 190, 365, 369 atrocarpi, 366 cincta, 366 cingulata, 190, 366, 370 gossypii, 194, 196, 369 lindemuthianum, 193, 369 piperata, 194, 366 psidii, 192 rubicola, 192 rufomaculans, 192 Glycyrrhiza, 141 Gnomonia, 190, 196, 346, 361, 365, 368, 372 caryae, 366 leptostyla, 198, 372 padicola, 346 ulmea, 197, 198 veneta, 196, 197, 346, 364, 366, 368 Gnomoniacese, 158, 189 key to genera of, 190 Gnomoniella, 361, 365 tubiformis, 361, 366 Gnomoniopsis, 190 Goldenrod, 135 Golden seal, 389 452 INDEX Gooseberry, 111, 172, 252, 268, 310, 356, 389 Gooseberry-mildew, 140 Gourd, 78, 409 Grain, 15, 151, 188, 342, 351 Gramineae, 108, 135 Grape, 39, 47, 177, 186, 248, 337, 340, 342, 346, 349, 351, 359, 366, 371, 375, 386, 401, 410, 413, 416 Grapefruit, 291 Graphiola, 230 Graphiothecium, 171 Grass, 151, 152, 153, 154, 186, 188, 222, 229, 271, 274, 275, 276, 351, 357, 402, 404, 410, 440 Grossularia, 253 Guava, 192, 366 Guignardia, 165, 166, 336, 338 ajsculi, 170, 337 bidwellii, 166, 337, 340 vaccinii, 170, 338 Gymnoascacese, 123 Gymnoconia, 254, 257, 279 interstitialis, 257 Gymnosporangium, 236, 254, 258, 280 blasdaleanum, 265 clavariseforme, 238, 260, 262 clavipes, 260, 264 germinale, 264 globosum, 260, 262 juniperinum, 263 juniperi-virginianae, 261 macropus, 260, 261 nelsoni, 260 nidus-avis, 260, 264 H Hackberry, 79, 377, 410 Hairy root, 39 Hamamelis, 142 Haplographieae, 396, 397 Hard gall, 39 Haustoria, 62, 74, 128 Hawthorn, 41, 180, 183, 264, 360, 363 Hazel, 92, 150, 177, 203, 368 Hedera, 177, 340, 359, 366 Helianthus, 36, 77, 134, 278 annuus, 135 Helicospora), 333 Helminthosporum, 188, 403, 404 avense-sativsB, 405 bromi, 189, 405 gramineum, 189, 404, 405 inaequalis, 407 inconspicuum, 407 No. 1, 406 sativum, 405, 406 sorokinianum, 406 teres, 404 trichostoma, 404 tritici-repentis, 189, 405 turcicum, 406 Helotiacese, 100 key to genera of, 101 Helvellales, 94, 99 Hemibasidii, 211 Hemisphaeriales, 95, 145, 362 Hemlock, 117, 161, 295, 297, 298, 300, 313, 315, 386, 389 Hemp, 47, 105, 205, 340, 344, 359 Hendersonia, 185, 354 foliicola, 354 mali, 354 Hepatica, 77, 256 Heracleum, 395 Herpotrichia, 159, 162 nigra, 162 Heteroecious, 232 HeteroEcism, 235, 236 Heterogamy, 56 Heterosporium, 402, 403 echinulatum, 403 gracile, 184 variable, 403 Heterotheca, lamarckii, 291 subaxillaris, 291 Heuchera, 142 INDEX 453 Hevea, 199 Hibiscus, 348 Hickory, 206, 306, 340, 368, 373 Hollyhock, 235, 277, 340, 342, 359, 371, 416 Honeysuckle, 39, 362 Hop, 5, 39, 79, 202, 340, 377, 379, 403 Hordeum, 135, 271, 431 nodosum, 224 silvaticum, 136 Hormodendrum, 397 cladosporioides, 176 hordei, 398 Horse chestnut, 149, 170, 319, 329, 340, 351, 359, 368, 386, 389 Horseradish, 72, 80, 351, 359, 389, 394, 410, 416 Humulus, 132, 134 Hyacinth, 39, 47, 108, 164, 188 Hyaloceras, 374 pachysporum, 374 Hyalodictyse, 333 Hyalodidymae, 333 Hyalophragmiae, 333 Hyalosporse, 333 Hyalostibese-Amerosporae, 416 key to genera of, 417 Hydnaceae, 286, 293 key to genera of, 293 Hydnum, 293, 294 coralloides, 294 erinaceus, 294 schiedermayeri, 294 septentrionale, 294 Hydrangea, 249, 340, 344, 359 Hymenium, 87 Hymenomycetes, 283 Hymenoscypha, 101, 109, 418 tumulenta, 110 Hyperplasia, 4 Hypertrophy, 4, 237 Hyphse, 51, 333 Hypochnus, 281 solani, 290 Hypocreales, 95, 146, 390 key to genera of, 147 Hypoderma, 121 — — deformans, 121 ■ — ■ — desmazieri, 121 laricis, 121 pinicola, 121 strobicola, 122 Hypodermataceae, 120 key to genera of, 121 Hypodermella, 121 larius, 121 Hypomyces, 147, 148, 393, 422 leptosphaerise, 424 rubi, 424 Hypothecium, 100 Hysteriacese, 362 Hysteriales, 94, 120 Ilex, 142 Illosporium, 418, 420 malifoliorum, 420 Impatiens, 77, 132 Infection, 17 experiments, 239 Involution forms, 12 Ipomcea, 242 Iris, 39, 43, 47, 184, 351, 359, 402, 403, 410 Isaria, 147 Isariopsis, 417 griseola, 418 Isogamy, 56 Ivy, 344, 346 Jerusalem artichoke, 43, 106 Johnson grass, 221 Juglans, 140, 351 June grass, 385 Juniperus, 162, 171, 236, 260, 300, 304, 355 barbadensis, 261, 263 454 INDEX Juniperus communis, 262, 264 oxycedrus, 262 — — sibirica, 262, 264 virginiana, 261, 263, 265 K Kalmia, 343, 359 Keithia, 116 thujina, 116 tsugsB, 116 Kuehneola, 246, 251 uredinis, 251 Kulti bean, 429 Kunkelia, 258 Lachnella, 101, 109 pini, 109 Lsestadia camellisB, 192 Lagenaria, 428 Larch, 108, 109, 121, 177, 248, 292, 298, 302, 304, 310, 313, 315, 362, 386, 389, 403, 434 Larkspur, 47 Lasiodiplodia, 352, 353 triflora), 353 tubericola, 353 Lathy rus, 176, 267 Laurus, 340 Legume, 32, 124, 266 Lemon, 27, 65, 105, 344, 389, 399 Lentinus, 319 conchatus, 320 lepideus, 320 Lenzites, 296, 317 abietina, 317 . betuhna, 317 sepiaria, 317 variegata, 317 viahs, 317 Lepargyrea, 275 Leptospha)ria, 178, 184, 355 Leptospha^ria avenaria, 185, 356 coniothyrium, 185, 349 napi, 408 " phlogis, 356 tritici, 186 Leptostroma, 360, 362 larcinum, 362 piricola, 362 punctiforme, 362 LeptostromatacesB, 335, 360 Hyalophragmise, 362 Hyalosporae, 360 key to genera of, 360 Leptothyrium, 196, 360, 361 alneum, 361 oxy cocci, 362 pomi, 362 Lespedeza, 141 Lettuce, 15, 30, 34, 39, 80, 105, 107, 291, 351, 358, 373, 386, 410 Leucosporeee, 322 Lilac, 70, 340, 389, 403 Liliaceae, 403 Lily, 177, 377, 386, 395, 41fi Lily of the valley, 359, 388 Lima bean, 39 Limacinia, 144 camellia), 144 citri, 144 penzigi, 144 Lime, 177, 348 Linaria, 124 Linden, 149, 150, 298, 359, 368, 375, 389, 416, 434 Liquidambar, 293 Liriodendron, 142, 368 Lobelia, 342 Locust, 297, 298, 311, 377 Lonicera, 140 Lophodermium, 121, 122 brachysponmi, 122 pinastri, 122 Loquat, 41, 192 Lupine, 47, 70, 124, 133, 375 Lycopersicum, 133 INDEX 455 M Macroconidia, 421 Macronemese, 408 Macrophoma, 205, 336, 343 fici, 344 tumefaciens, 343 Macrosporium, 188, 408, 409 alliorum, 410 commune, 410 fasciculata, 413 lycopersici, 413 porri, 410 rugosa, 413 sarcinula, 410 tomato, 413 Magnolia, 142, 181, 340 Mahonia, 271 Mal-di-gomma, 433 Manginia, 366 Mangel, 42 Mango, 192 Mangold, 342 Maple, 120, 137, 149, 150, 206, 294, 298, 306, 308, 312, 313, 316, 325, 340, 348, 351, 359, 360, 362, 367, 368, 373, 377, 416 Marasmiese, 318, 319 key to genera of, 319 Marasmius, 319, 326 plicatus, 320, 321 Marssonina, 110, 196, 372 castagnei, 372 juglandis, 198, 372 panattoniana, 373 perforans, 373 populi, 372 violae, 373 May apple, 235 Medicago, 133 Medick, 110 Melampsora, 245, 246, 279 lini, 246 medusso, 247 saliciscapra), 248 Melamsporacese, 241, 245, key to genera of, 245 Melampsorella, 246, 250, 279, 280 elatina, 250 Melampsoridium, 280 Melampsoropsis, 280 Melanconiaceae, 364 Hyalodidymae, 372 Hyalophragmea^, 373 HyalosporsB, 364 key to genera of, 365 -PhsBophragmiae, 374 key to genera of, 374 -- -Phaeosporse, 371 -Scolecospora), 376 Melanconiales, 191, 334, 364 MelanconidacetB, 158, 202 Melanconium, 371 fuligineum, 371 — ■ — pandani, 372 sacchari, 372 Melasmia, 360, 362 — — acerina, 120, 362 punctata, 362 saUcina, 362 Melilotus, 351 Meliola, 144 Melogrammataceae, 158, 203 key to genera of, 204 Melon, 28, 410 Mentha, 134 Mesospore, 234 Mespilus, 379 Micrococcus, 14, 18 Microconidia, 421 Micronemeae, 408 MicrosphsBra, 131, 139 alni, 140 diffusa, 140 euphorbiae, 141 grossularise, 139 MicrothyriacesB, 145 Mignonette, 72, 416 Millet, 75 Mint, 278 456 INDEX Mollisiacea>, 100, 110 key to genera of, 110 Monilia, 101, 102, 104, 378, 379 cinerea, 103 fructigena, 104 seaveri, 104 Moniliacea), 377, 378, 422 Amerosporae, 378 key to groups of, 378 Didymosporea), 391 key to genera of, 391, 393 Phragmosporse, 393 key to genera of, 393 Scolecosporse, 395 Moniliales, 334, 377 key to families of, 377 Monilocha)tes, 396, 397 inf uscans, 397 Monocha)tia, 374 Monocotyledons, 403 Moon flower, 73 Morfea, 144 Morning glory, 73, 242 Morus, 177, 360 Mountain ash, 41, 263, 264, 305 Mucor, 84 Mucoracea), 85 Mucorales, 56, 84 key to families, of, 85 Mulberry, 21, 32, 149, 150, 181, 319, 325, 342, 348, 350, 353, 360, 376, 416 Mushroom, 28, 148, 393 Musilago spongiosa, 8 Muskmelon, 15, 44, 46, 47, 78, 174, 340, 410 Myceha steriHa, 334, 435 key to form genera of, 435 Mycelium, 50 Mycena, 322, 329 epipterygia, 329 Mycetozoa, 3, 7 Mycogone, 148, 391, 392 perniciosa, 148, 393 rosea, 148, 393 Mycoi)lasm theory, 238 Mycospha>rella, IQ5, 171, 336, 340, 355, 394, 360, 399, 413 aurea, 172 brassicicola, 176, 337 cerasella, 172, 413 citrullina, 174, 351 fragaria?, 171, 356, 394 • gossypina, 176, 413 grossularise, 172 larcina, 362 — — maculiformis, 337, 376 morifolia, 376 nigerristigma, 173 ontarioensis, 176 pinodes, 176 populi, 356, 417 rosigena, 177 rubi, 173, 356 rubina, 172 sentina, 173, 356 tabifica, 175, 337, 340 tulasnei, 175, 399 — ulmi, 176, 337 Mycospha)rellacese, 158, 165 key to genera of, 165 Myriangiaceae, 126 Myriangiales, 94, 125 Myriangium, 126 Myxomycetes, 2, 3 Myxosporium, 196, 365, 368 acerinum, 368 corticolum, 368 valsoideinn, 196, 368 N Napicladium, 402, 404 janseanum, 404 soraueri, 404 Narcissus, 340, 359, 395, 403, 427 Nasturtium, 22, 36, 124, 188 Nectarine, 33, 400 Nectria, 147, 148, 418, 419, 422 cinnabarina, 148, 149, 419 INDEX 457 Nectria cucurbitula, 149 ditissiina, 149, 424 gallisena, 149, 424 graminicola, 150 Nematospora, 92 coryli, 92 phaseoli, 93 Neocosinospora, 147, 422 Neofabraia, 110, 111 malicorticis, 112 Neonectria, 422 ramiilaria>, 424 Neopeckia, 159, 161 coulteri, 161 Neozimmermannia elasticse, 192 Nicotiana, 134 Nummularia, 207 discreta, 207, 208, 209 Nut trees, 315 Nyssa, 293 o Oak, 133, 149, 150, 164, 177, 180, 181, 197, 199, 200, 206, 253, 291, 293, 294, 297, 298, 300, 301, 304 306, 308, 312, 316, 323, 340, 346, 347, 351, 353, 368, 373, 379, 401 Oat, 23, 27, 151, 152, 188, 214, 216, 271, 275, 357, 369, 401, 402, 405, 407 Oat grass, 217 Odontoglossum, 416 Oidium, 378, 379 ambrosise, 134 balsamii, 133 chrysanthemi, 379 cratsegi, 138 erysiphoides, 379 ■ farinosum, 139 fragarijB, 131 leucoconium, 132 mespilinum, 379 monilioides, 135 ■ querciniim, 379 tabaci, 379 Oidium tuckcri, 136 verbena), 379 Okra, 87, 350, 351, 390, 416, 428 Oleander, 39, 359, 416 Olive, 34, 340, 344, 398, 413 Oncidium, 401 Onion, 43, 47, 81, 106, 143, 278, 380, 389, 410, 428, 433, 440 Oochytriacea), 57, 61 Oogonium, 53, 56 Oomycetes, 56, 57 Oosphere, 53, 56 Oospora scabies, 48 Oospore, 53, 56 OosporesB, 378 key to genera of, 378 Ophiobolus, 178, 186 cariceti, 186, 187 graminis, 186 Orange, 144, 188, 293, 312, 319, 348, 353, 383, 399, 408, 409, 411 Orchard grass, 17, 21, 369 Orchid, 5, 21, 47, 366, 368, 371, 389, 416 Ornithogalum, 229 umbellatum, 275 Ostiole, 332 Ostrya, 96, 142 Ovularia, 171, 385, 389 armoracia), 389 canaegricola, 389 interstitialis, 389 primulana, 389 Ovulariopsis, 142 Oxalis, 236, 276 Ozonium, 435, 440 omnivorum, 440 PsGonia, 133 Palm, 65, 192, 368, 371, 375, 434 Pandanus, 372 Panicum, 215, 220 crus-galli, 216, 222 Pansy, 83, 229, 371, 433 458 INDEX Parasites, 1 Paraphyses, 87 Parsley, 105, 341, 357 Parsnip, 39, 42, 77, 341, 395, 415 Palownia, 368 Pea, 33, 36, 124, 176, 188, 236, 371, 401, 428, 433 Peach, 33, 39, 86, 97, 102, 132, 164, 165, 180, 203, 256, 306, 366, 326, 340, 342, 353, 395, 400, 401 Peanut, 36, 270, 416 Pear, 15, 40, 69, 86, 112, 133, 149, 164, 174, 180, 182, 202, 263, 265, 289, 298, 339, 340, 356, 362, 363, 368, 401 Pecan, 140, 177, 205, 340, 349, 359, 368, 402, 416 Peckiness, 302 Pelargonium, 39, 368, 433 Pellicularia koleroga, 289 Penicillium, 123, 125, 380, 381, 417 crustaceum, 382 digitatum, 383, 384 expansum, 381 glaucum, 381, 382 italicum, 382 Peony, 387, 389, 401 Pepper, 70, 194, 366, 370, 410, 416 Peridermium, 236, 239, 241, 251, 278, 279 key to assignment of species, 280 acicolum, 243 cerebrum, 253 elatinum, 250 filamentosum, 253 ipomoea), 242 oblongisporium, 243 pyri forme, 252 rostrupi, 244 strobi, 251 Peridium, 100, 232 Perisopriaceae, 127, 142 Perisporiales, 90, 94, 127 key to families of, 127 Perithccium, 52, 87 Pcritrichiate, 10 Peronospora, 74, 80 efTusa, 80, 81 hyoscyami, 83 parasitica, 80 schleideni, 81, 82 trifoliorvim, 81 vicise, 81 Peronosporacese, 63, 73 key to genera, 74 Peronosporales, 56, 62 key to families, 63 Persimmon, 368, 389 Pestalozzia, 374 funerea, 374 guej)ini var. vaccinii, 375 hartigii, 374 uvicola, 375 Petunia, 36, 105 Pezizales, 94, 100 key to families of, 100 Phacidiacea), 116 key to genera of, 1 16 Phacidiales, 94, 115 Phacidiea), 116 Pha}odicty8e, 333 Pha)odidymiB, 333 Pha)ophragmiaB, 333 Pha)ospor8R, 333 PhseosporefE, 320 Phseostilbeae-PhragmosporaR, 417 Phakopsora, 245, 248 vitis, 248 Phaseolus, 133, 141, 266, 429 Phleospora, 171, 355, 359 mori, 360 ulmi, 176 Phleum, 135, 229, 402 Phlox, 132, 134, 186, 356, 359, 416 Pholiota, 320, 323 adiposa, 322, 323 aurivilla, 323 cervinus, 323 destruens, 323 INDEX 459 Pholiota mutabilis, 323 spectabilis, 323 squarrosa, 323 Phoma, 166, 171, 172, 175, 185, 188, 200, 336, 340 albicans, 340 ambigua, 340 apiicola, 341 batata, 201 beta), 175, 340 bohemica, 340 destructiva, 341 lingam, 341 oleracea, 341 piceina, 341 pomi, 340 reinformis, 340 sarmentella, 340 solani, 343 sphaerosperma, 175 subcircinata, 202 uvicola, 166, 338 vexans, 343 Phomopsis, 336, 342 californica, 342 citri, 342 kalmise, 343 mali, 342 stewartii, 342 vexans, 343 Phragmidium, 254, 256, 279 americanum, 256 disciflorum, 256 montivagum, 256 rcsse-arkansanse, 256 calif ornicse, 256 setigerse, 256 Phragmitis, 270 Phragmospora), 333 Phycomycetes, 50, 55, 56 key to orders, 56 Phyllachora, 154, 401 graminis, 154 trifolii, 401 Phyliactinia, 127, 129, 131, 141 PhyHactinia corylea, 141 Phyllactinieae, 131 Phyllosticta, 166, 170, 171, 335, 336 althaeina, 340 apii, 339 bellunensis, 337 betsB, 339 beyerinckii, 165 brassicae, 337 brassicicola, 176 caryae, 340 chenopodii, 339 circumscissa, 339 congesta, 338, 339 cucurbitacearum, 339, 416 labruscae, 166, 337 limitata, 339 maculiformis, 337 pavise, 170, 337, 338 phaseolina, 339 pirina, 339 primicola, 339 solitaria, 337, 338 sphseropsidea 170, 337 straminella, 340 tabifica, 175, 337 Physalis, 36, 230 Physalospora, 178, 365 cattelysB, 366 cydoniae, 179, 180, 348 Physarum cinereum, 7, 8 gyrosum, 8 Physoderma, 60 zeae-maydis, 60 Phytolacca decandra, 291 Phytophthora, 63, 66, 69 cactorum, 69 capsici, 70 infestans, 67, 68 omnivora, 68 parasitica, var. rhei, 69 phaseoli, 66, 67 terrestria, 69 Picea, 291 460 INDEX Piggotia, 360 Pigweed, 291 Pine, 21, lOS, 109, 115, 119, 121, 122, 150, 161, 162, 164, 242, 243, 252, 253, 280, 297, 298, 300, 302, 309, 310, 313, 315, 325, 342, 353, 355, 358, 386, 389, 428, 438 Pineapple, 396 Pink, 250, 351 Pin rot, 302 Pinus, 252, 253, 279, 291 cembra, 252 echinata, 242 edulis, 253 monophylla, 253 rigida, 245 sylvestris, 244 virginiana, 244 Pionnotes, 421, 422 Piricularia, 393, 395 grisea, 395 Pisum, 133 sativum, 429 Plantain, 44 Plasmodiophora, 3, 4 brassicsB, 4, 5 Plasmodiophoracese, 3 key to genera, 3 Plasmodium, 3 Plasmopara, 74, 76 viticola, 76, 77 Platanus, 140, 364 Plectodiscella, 125 veneta, 125, 126 PlectodiscellesD, 125 Plenodomus, 336, 344 destruens, 344 f uscomaculans, 344 Pleosphaeria, 144 Pleospha^rulina, 165, 177 briosiana, 178 Pleospora, 178, 188, 404, 409, 410 albicans, 340 bromi, 189, 405 gramineum, 189, 404 Pleospora herbarum, 410 hesperidearum, 408 trichostoma, 189, 404, 410 tritici-repentis, 189, 405 tropeoli, 188, 410 vulgaris, 403 Pleosporacea), 158, 178 key to genera of, 178 Pleurotus, 322, 324 atrocseruleus, 325 corticatus, 325 mitis, 325 ostreatus, 324, 325 salignus, 325 ulmarius, 325 Plowrightia morbosa, 156 Plum, 33, 40, 86, 98, 118, 138, 156, 199, 203, 256, 310, 326, 339, 356, 359, 400 Pluteus, 320, 324 cervinus, 324 Poa, 135, 220, 229, 230, 274 Podospha)ra, 131, 137 leucotricha, 138 oxyacanthse, 138, 139 tridactyla, 138 Polemonium, 351 Polymorphism, 55 Polyporacese, 286, 295 key to genera of, 296 Polyporea), 296 Polyporus, 296, 297 adustus, 304 amarus, 301 betulinus, 303 borealis, 300, 302 dryadeus, 301 dryophilus, 300 giganteus, 300 gilvus, 300 hisi)idus, 299 obtusus, 297 l)inicola, 286 schweinitzii, 286, 302 squamosus, 298, 299 INDEX 461 Polyporus sulphureus, 297, 298 Polystictus, 296, 304 cinnabarinus, 304 hirsutus, 305 pergamenus, 304 sanguineus, 304 velutinus, 304 versicolor, 304 Polythrincium, 398, 401 trifolii, 401 Pomaceous trees, 182, 203, 260, 292, 382, 401 Pome, 103, 104, 199 Pomegranates, 380 Pomelo, 192, 399 Poplar, 39, 47, 137, 177, 248, 292, 294, 298, 300, .304, 311, 315, 317, 320, 323, 325, 343, 344, 348, 351, 353, 359, 368, 372, 373, 401, 417 Poppy, 230 Populus, 96, 248, 356 Poria, 296 laevigata, 296 subacida, 297 vaporaria, 296 weirii, 297 Potato, 5, 15, 35, 41, 42, 45, 48, 58, 64, 67, 86, 105, 164, 186, 291, 326, 342, 390, 407, 408, 412, 414, 427, 428, 429, 430, 431, 432, 437 Powdery mildew, 127 Primrose, 83, 177, 229, 340, 351, 371, 386, 389, 395 Privet, 192, 366 Promycelium, 54, 56, 213, 323 Protoascomycetes, 88, 91, 92 Protobasidii, 211, 230 Protodiscales, 88, 94, 95 Prunaceous hosts, 403 Prunus, 99, 119, 137, 138, 149, 256, 339, 345, 346, 353, 376, 386, 389, 414 americana, 99, 118 avium, 98, 117 cerasus, 98, 117 Prunus domestica, 118 insititia, 1 18 mahaleb, 1 18 maritima, 99 nigra, 99 padus, 104 pennsylvanica, 117, 173 pumila, 99 serotina, 104, 118 spinosa, 118 virginiana, 118, 119 Pseudomonas, 14, 15, 21 angulata, 17, 21 apii, 22 aptata, 22 atrofaciens, 22 avense, 23, 41 beticola, 23 campestris, 17, 23, 24, 25, 30, 32, 44 cannaB, 26 cerasi, 26 citraref aciens, 26 citri, 26 citriputealis, 27 coronafaciens, 27 destructans, 44 dissolvens, 27 erodii, 28 flaccumf aciens, 27 fluorescens, 28 glycinea, 28 juglandis, 17, 28 • lachrjnmans, 17, 29 maculicola, 29 malvacearum, 17, 30 marginalis, 30 medicaginis, 30 mellea, 31 michiganense, 20 mori, 32 olese-tuberculosis, 34 papulans, 32 pelargoni, 32 phaseoli, 17, 32 462 INDEX Pseudomonas pisi, 33 pruni, 17, 33 rhizoctonia, 34 savastanoi, 17, 34 solanacearum, 17, 20, 35, 36, 45 stewarti, 18, 19 — — tabaci, 36 translucens, 37 var. undulosa, 37 tumefaciens, 17, 37 vesicatoria, 28 vigna), 39 viridilivida, 39 vitians, 39 • woodsii, 39 Pseudoperonospora, 74, 78 celtidis, 79 cubensis, 78 humuli, 79 — — portoricensis, 79 Pseudopeziza, 110, 365, 369, 372 — — medicaginis, 110 ribis. 111, 366 salicis, 366 trifolii. 111, 345, 364 Pseudopionnotes, 421 Pseudotsuga, 291, 295 Pteris, 340 Puccinia, 255, 268 arachidis, 270 asparagi, 233, 236, 237, 268 chrysanthemi, 277 coronata, 274 dispersa, 273 — — fraxinata, 270 — ■ — glumariim, 275 graminis, 240, 270 agrostis, 271, 272 — — airse, 271 avena), 271, 272 phlei-pratensis, 271, 272 poa3, 271 secalis, 271, 272 tritici, 271, 272 compact!, 271, 272 Puccinia helianthi, 278 hieracii, 270 malvacearum, 276, 277 phragmitis, 269 poarum, 276 podophyllii, 239 pringsheimiana, 268 purpurea, 276 ribis-caricis, 268 simplex, 275 sorghi, 275, 276 subnitens, 270 triticina, 274 vexana, 234 Pucciniacese, 241, 254, 279 key to genera of, 254 Pucciniastrum, 246, 248, 279, 280 hydrangese, 249 Pumpkin, 78, 87, 194, 291 Purslane, 73, 291 Pycnia, 231, 232 Pycnidia, 52, 89, 332 Pycnosclerotia, 170 Pyrenomycetes, 126 Pyrenopeziza, 110, 113 medicaginis, 113, 114 Pyrenophora, 178 t richest oma, 189 Pyronema, 90 Pyropolyporus pra^rimosa, 308 Pyrus, 132, 138, 262, 361 Pythiacese, 63 Pythiacystis, 63, 65, 66 citrophthora, 65 Pythium, 63, 64 aphanidermatum, 65 debaryanum, 64 Q Quercus, 96, 140, 142 Quince, 39, 86, 112, 113, 177, ISO, 192, 264, 265, 289, 342, 355, 363, 373 INDEX 463 R Radish, 39, 72, SO, 291 Ramularia, 171, 393, 394, 424 ■ — — - armoraciiae, 394 Candida, 424 magnusiana, 424 rubi, 432 tulasnei, 171, 394 Rape, 105, 186 Raspberry, 86, 125, 172, 176, 185, 257, 389, 391 Rathay's disease, 17 Redbud, 359, 416 Red Cedar, 236 Red top, 220 Rehmielliopsis, 340 Ehabdospora, 355, 359 oxycocci, 359 rubi, 359 Rhamnus, 275 Rhizina, 99 inflata, 99 undulata, 99 Rhizinacese, 99 Rhizoctonia., 435 — — crocorum, 436 — — medicaginis, 436 microsclerotia, 438 solani, 290 436 Violacese, 436 Rhizopus, 85, 86 nigricans, 85 tritici, 86 Rhododendron, 186, 288 Rhodosporeae, 320 Rhopalocystis, 380 Rhubarb," 43, 69, 270, 340, 346, 351, 370 Rhynchosporiuni; 391, 392, 393 graminicola, 393 secaHs, 393 Rhytisma, 116, 119, 362 acerinum, 120, 362 punctatum, 120 Rhytisma saHcinum, 120 symmetricum, 120 Ribes, 132, 133, 140, 142, 172, 192, 235, 248, 252, 253, 268, 340, 366 Rice, 153, 177, 186, 188, 199, 225, 340, 345, 353, 355, 359, 395, 401, 404, 410, 433, 440 Richardia, 291 Ricinus, 36, 433 communis, 107 Robinia, 359 Roesteha, 259, 260, 278, 280 aurantiaca, 264 penicillata, 263 pyrata, 261 Rosa, 132 Rosacese, 96, 108 Rosaceous, 16, 280, 403 Rose, 39, 47, 83, 132, 146, 177, 201, 202, 257, 310, 340, 349, 368, 373, 375, 386, 392, 416 Roselle, 141 RoselUnia, 159, 163, 417 car y 86, 164 massinkii, 164 necatrix, 163 quercina, 164 radiciperda, 164 Rostrum, 332 Rubber, 192, 291 Rubus, 83, 132, 173, 192, 251, 359, 366, 416, 428 Rumex, 270, 389 Rust fungi, 231 Rutabaga, 25, 28, 106 Rye, 27, 136, 151, 152, 186, 188, 189, 224, 228, 271, 274, 275, 358, 369, 373, 393, 406 s 185, 359, 326, Saccharomycetacese, 92 Saccharomycetales, 92 key to f amiUes of, 92 464 INDEX Saccharum, 135 Saffron, 438 Sainfoin, 395 Salix, 248, 366, 401 Salsify, 39, 73, 408 Saltation, 404 Sambucus, 140 Sapindacea), 97 Saponaria, 410 Saprolegniales, 63 Saprophytes, 1 Sarcinula parasiticum, 410 Sassafras, 310 Satsumas, 399 Scabiosa, 132, 133 Schizomycetes, 2, 9, 13 key to orders, families, and genera, 14 Schizophyllea), 318 Schizophyllum, 318 alneum, 318 Scilla, 108 Sclerospora, 74, 75 graminicola, 75, 76 maerospora, 75 philippinensis, 76 spontanea, 76 Sclerotinia, 101, 386 bulborum, 108 cinerea, 102, 103 fructigena, 102, 103, 104 fuckeliana, 386 laxa, 102 ledi, 101 libertiana, 105 minor, 107 nicotiana), 107 oxycocci, 104 padi, 104 panicis, 107 perplexa, 106 ricini, 107 sclerotiorum, 104, 105, 106, 107 seaveri, 104 Sclerotinia smilacina, 107 trifoliorum, 108 urnula, 102 Sclerotium, 435, 438 bataticola, 439 oryza3, 440 rhizodes, 440 rolfsii, 438 ScolecosporsB, 333 Scolecotrichiim, 398, 402 graminis, 402 Secale, 135, 136, 271 Sedum, 346, 359 Seedlings, 69 Senecio, 244 Sepedonium, 148 Septa, 50 Septobasidiiim, 287, 292 pseiidopedicellatum, 293 Septocylindrium, 393 areola, 394 rufomaculans, 394 Septogloeum, 171, 373 cydoniae, 373 fraxini, 373 hartigianum, 373 profusum, 373 ulmi, 177 Septoria, 171, 185, 355 aciculosa, 356 agropyri, 358 apii, 357 aurea, 172 avenae, 185, 356 bataticola, 356 beta), 357 — — bromi, 358 citriilli, 357 consimilis, 358 cucurbitacearum, 357 fragariae, 356 gladioli, 359 graminum, 356 lactucse, 357 lycopersici, 357 INDEX 465 Septoria nodorum, 358 parasitica, 351 passerinii, 358 petroselini, 357 phlogis, 356 piricola, 174, 356 populi, 356 primi, 356 ribis, 172, 356 rubi, 173, 356 secalis, 358 spadicea, 358 tritici, 359 Sequoia, 171, 416 Setaria, 153, 215 italica, 75 Shadbush, 41 Slime molds, 2 Smut fungi, 211 Snapdragon, 235, 359, 371, 390 Snowdrop, 389 Soft gall, 39 Soft rot, 16, 17, 44 Solanacese, 124 Solanaceous plants, 15, 67 Solanum, 230, 431 nigrum, 36 verbascifolium, 291 Solidago, 243 Sooty molds, 144 Sorbus, 183, 401 Sordariaceae, 157, 158 Sorghum, 76, 220, 221, 222, 276, 407 Soy Bean, 28 Spelt, 151 Sperm, 53, 56 Spermatia, 89 Spermogonia, 231 Sphacelia, 147, 418, 420 segetum, 151, 420 Sphaceloma ampelinum, 366 Sphacelotheca, 214, 220 diplospora, 222 Sphacelotheca relHana, 221, 222 Sphacelotheca sorghi, 220 Sphcerella, 171, 172 Spha^riaceae, 157, 159 — ■ — key to genera of, 159 Sphseriales, 95, 157 — ■ — key to families of, 157 Si)ha3rioidace8e, 335 Hyalodidymae, 350 key to genera of, 350 Hyalophragmiae, 354 Hyalosporse, 335 key to genera of, 335 — Phaeodidymse, 352 key to, 352 Phseophragmise, 354 Phseosporae, 348 key to genera of, 348 -Scolecosporse, 355 key to genera of, 355 Sphaeronema, 336, 345 fimbriatum, 345 phacidioides, 345 Sphaeropsidales, 334, 335 — — key to famihes of, 335 Sphaeropsis, 348 cydoniae, 179 malorum, 179, 348 tumefaciens, 348 Sphaerostilbe, 147, 422 — ■ — coccophila, 424 Sphaerotheca, 128, 131 ■ castagnei, 89 humuh, 131 var. fuliginea, 132 — ■ — lanestris, 133 mors-uvae, 132 pannosa, 132 Spha)rulina, 165, 177 ^trifolii, 177 Spicaria, 148, 422 Spinach, 81, 230, 270, 239, 370, 395, 401, 403, 415, 416, 429 Spiny pigweed, 291 Spirea, 132, 138, 359 Spondylocladium, 403, 407 466 INDEX Spondylocladium atrovirens, 407 Spongospora, 3, 5 subterranea, 5, 6 Sporangiophore, 52 Sporangium, 52 Spore, 1 1 Spore germination, 11 Sporidia, 54, 213, 233 Sporodesmium, 185, 188, 408 exitiosum, 408 — ■ — piriforme, 408 Sporodochia, 333, 421 Sporonema, 196, 363, 364 oxycocci, 364 — — ^ phacidioides, 113, 364 -^— platani, 197, 364 pulvinatum, 364 Sporotrichum, 163, 385, 422 — — poa), 385 Spruce, 109, 150, 162, 280, 294, 296, 297, 300, 302, 304, 308, 313, 315, 341, 351, 386, 389 Spruce fir, 150 Squash, 78, 86, 135, 194, 409 Stagonospora, 354 carpathica, 354 iridis, 354 Staurosporse, 333 Steccherinum, 293, 295 — — ballonii, 295 Stemphylium, 408 ^citri, 409 cucurbitearum, 409 ^tritici, 409 Stereum, 287, 291 frustulosum, 291 — — hirsutum, 291 purpureum, 292 Sterigmata, 52, 210, 233 Sterigmatocystis, 380 castanea, 380 Stigmatea, 165, 171, 172 juniperi, 171 Stilbacea), 377, 416 Stilbella, 417 Stilbella populi, 417 Stilbum, 417 Stizolobium, 21 Stone fruits, 199 Strawberry, 41, 83, 86, 132, 171, 181, 340, 344, 351, 356, 362, 368, 373, 386, 394, 395 Stroma, 87 Subiculum, 87 Sugar beet, 22, 42, 291, 403 Sugar cane, 39, 47, 76, 160, 177, 186, 319, 320, 345, 369, 372, 375, 396 Sumac, 206 Sunflower, 106, 229, 359 Surface parasitism, 17 Swarm spores, 53 Sweet orange, 192 Sweet pea, 44, 124, 140, 192, 433, Sweet potato, 7, 73, 86, 201, 242, 291, 340, 342, 344, 345, 353, 356, 359, 379, 395, 397, 401, 427, 428, 439 Sycamore, 197, 346, 359, 360, 366, 368, 375, 389, 401 Symphoricarpus, 141 Symphytum, 133, 134 Synchytriacese, 57, 58 Synchytrium, 58 — ■ — endobioticum, 58 vaccinii, 59, 60 Syringa, 39, 140 Take-all, 186 Taphrina, 95, 96 ^— bullata, 99 cerasi, 98 communis, 99 cratsegi, 99 decipiens, 99 deformans, 97, 98 — — farlowii, 99 — ■ — institia), 99 longipcs, 99 INDEX 467 Taphrina inirabilis, 99 pruni, 98 rhizipes, 99 Taphrinopsis, 96 Taraxacum, 132 Tea, 192, 291, 417 Tecoma, 416 Teleuto-sori, 232 Telia, 322 Teliospore, 233 Teosinte, 61 Thalictrum, 236, 256, 274 Thelephoracea), 286, 287 Theobroma, 192 Thielavia, 123 basicola, 123, 124 Thielaviopsis, 396 ethaceticus, 160 paradoxa, 396 Thistle, 235 Thrombosis, 16 Thuya, 297 Tilletia, 213, 222, 223 horrida, 224 laevis, 223 texana, 224 tritici, 223, 224 Tilletiacese, 213, 222 — — key to genera of, 222 Timothy, 23, 219, 220, 275, 369 Tobacco, 22, 28, 31, 36, 70, 83, 107, 124, 188, 340, 351, 359, 379, 410, 413, 414, 433 Tomato, 5, 20, 21, 28, 35, 39, 43, 67, 70, 86, 341, 357, 370, 400, 401, 412, 413, 421, 427, 428, 429, 431 Torulese, 396 key to genera of, 396 Toxins, 2 Tragopogon, 133, 134, 220 Trametes, 296, 314 pini, 286, 314 — ■ — • radiciperda, 286, 308 Trametes suaveolens, 315 Tranzschelia, 254, 255 — ■ — punctata, 255, 256 Trees, 440 Tremella, 281 Trichoderma, 379 koningi, 379 Trichogyne, 89, 90 Trichospha^ria, 159, 160, 396 sacchari, 160 Trichothecium, 422 Trifolium, 111, 133, 268 incarnatum, 267 — ■ — pratense, 134 • — — repens, 267 Trimmatostroma, 434 abietina, 434 Triticum, 135, 271, 431 dicoccum, 135 repens, 188, 189 Trochila, 365, 372 — — craterium, 366 populatum, 372 Tropoeolum, 22, 72, 410 True fungi, 50 Tsuga, 248, 280 Tubercularia, 147, 148, 418, 419 fici, 419 vulgaris, 148, 419 Tuberculariacea), 377, 418, 421 Dematiese-Phragmosporae, 434 key to genera of, 434 Mucedineae-Amerosporse, 418 key to genera of, 418 Mucedinese-Phragmosporae, 421 Tulip, 69, 108, 220, 388, 440 Tumor, 16, 17, 38 Turnip, 25, 39, 42, 72, 80, 371, 395, 410 Typha, 142 u Ulmus, 142 Umbellifera), 4, 77, 278, 395, 401 Unicinula, 131, 136 Unicinula aceris, 137 468 INDEX Unicinula circinata, 137 clandestina, 137 — — • flexuosa, 137 — ■ — necator, 136 • prunastri, 137 salicis, 137 Uredinales, 230, 282 key to families of, 241 -imperfecti, 241, 278 key to, 278 Uredinia, 232 Uredinopsis, 280 Uredo, 278, 280 muelleri, 251 Uredo-sori, 232 Urocystis, 213, 222, 225 agropyri, 228 — cepula), 225, 22G — occulta, 228 'tritici, 227 violse, 228 Uromyces, 255, 265, 279 — ■ — • appendiculatus, 266 -betae, 268 • caryophyllinus, 268 ^fabae, 266 — fallens, 267 medicaginis, 267 — — oblongus, 268 — pisi, 237 ^trifolii, 267 Urophlyctis, 61 — alfalfa?, 61, 62 Ustilaginaceae, 213, 214 key to genera of, 214 Ustilaginales, 211 key to families of, 213 Ustilaginoidea, 147, 153 — — virens, 153 Ustilago, 213, 214 avense, 214 crameri, 216 crus-galli, 215 hordei, 216 levis, 216, 217 Ustilago macrospora, 216 nuda, 216 perennans, 217 — ■ — sacchari, 216 striseformis, 219 tritici, 217 — zeae, 218, 219 V Vaccinium, 138, 170, 288 Valeriana, 133, 134 Valsa, 199 leucostoma, 199, 200 Valsacea), 158, 199 — — key to genera of, 199 Valsonectria, 336 Vanilla, 21, 36 Vascular diseases, 15, 17 Velvet bean, 21 Venturia, 178, 181, 401 cerasi, 401 — — • chlorospora, 401 ditricha, 401 fraxini, 401 inaequalis, 182, 183, 401, 404 — • var. cinerascens, 401 pirina, 182, 401 pomi, 182 tremulsB, 401 Verbena, 132, 133, 134, 379 Vermicularia, 336, 346 dematium, 346 Veronica, 359 Verticillia), 378, 389 key to genera of, 389 Verticillium, 147, 389, 390 albo-atrum, 390 Vetch, 176, 351 Viburnum, 289 Vicia, 133, 267, 389 ma jus, 424 Vigna (cowpea), 133 sinensis, 429 Vinca, 278, 340, 350 INDEX 469 Viola, 132 Violet, 83, 124, 228, 278, 340, 368, 373, 395, 410, 416 Vitis, 76, 136, 192 Volutella, 148, 420 — ■ — circinans, 143 fructus, 420 leucotricha, 420 lycopersici, 421 Volvaria, 320, 323 bombycina, 323 w Walnut, 15, 28, 150, 199, 298, 308, 347, 351, 359, 372, 373, 401 Water-lilies, 230, 416 Watermelon, 78, 194, 291, 416, 428, 431 Wheat, 22, 27, 37, 135, 151, 186, 188, 214, 218, 223, 224, 236, 271, 274, 275, 342, 357, 359, 369, 393, 406, 409 Willow, 39, 47, 120, 137, 181, 292, 298, 306, 311, 315, 325, 351, 362, 368, 373, 375, 389, 351, 416 Wistaria, 21 Witch hazel, 180 Witches' broom, 237, 250, 251, 432 X Xanthium, 390 Xanthoxylum, 142 Xylaria, 207, 210 digitata, 210 — — hypoxylon, 210 polymorpha, 210 306, XylariaceaB, 158, 207 377, key to genera of, 207 z ' Yeast, 92 jg2 Yew, 177, 344 228, 358, Zea, 276, 431 Zinnia, 105 248, Zoospores, 53 348, Zygomycetes, 56, 83 f^ <.^^ nF ^^ o<#- SB 733.S85 3 9358 00023078 6 CHEM SB733 S85 Stevens, Frank Lincoln, 1871-1934. Plant disease Fungi, by F« L« Stevens* •• New York, The Macmiiian company [cl925] V, 2 Jt • , 469 p« illus* 23 cm* 23078 m