IOWA STATE COLLEGE JOURNAL OF SCIENCE Published on the first day of October, January, April and July EDITORIAL BOARD EDITOR-IN-CHIEF, R. E. Buchanan. ASSOCIATE EDITORS: P. E. Brown, Secretary; C. J. Drake, A. H. Fuller, I. E. Melhus, E. A. Benbrook, P. Mabel Nelson, V. E. Nelson. ADVISORY EDITORS: (From the Iowa State College Chapter of Sigma Xi): E.W. Lindstrom, Jay W. Woodrow, 0. R. Sweeney. EDITORIAL COMMITTEE: R. E. Buchanan, Chairman; C. J. Drake, E. W. Lindstrom, I. E. Melhus, P. Mabel Nelson, 0. R. Sweeney. BUSINESS COMMITTEE: P. E. Brown, Chairman; A. H. Fuller, V. E. Nelson, Jay W. Woodrow . .All manuscripts submitted for publication should be addressed to R. E. Buchanan, Room 101 Science Building, Iowa State College, Ames, Iowa. All remittances should be addressed to P. E. Brown, Bus. Mgr., Room 25 Hall of Agriculture, Iowa State College, Ames, Iowa. Single Copies: One Dollar; Annual Subscription Three Dollars; In Can­ ada, Three pollars and a Quarter; Foreign, Three Dollars and a Half. A SUMMARY OF THE son.. FUNGI By J. C. GILMAN and E. V. ABBOTT From the Laboratory of Plant Pathology, Iowa State College, and the Laboratory of the Soils Sectton, Iowa .Agricultural Experiment Statton Submitted for publication, February 22, 1927 The key to soil fungi presented here is the outgrowth of a study of the fungus flora of soils which has extended over a period of nearly five years. During the course of the work several hundred isolations were made from soils in Iowa and Louisiana, while a less systematic study was made of soils from other sources as opportunity arose. The key is intended to include all of the species of fungi which are reported in the literature as having been isolated from the soil, in addition to those which are reported for the first time by the authors. Certain exceptions are noted under the different genera. It is realized of course, that in the future many additional fungi will be isolated from the soil which are not included here. It is also probable that some species have been isolated from the soil which have not been for­ mally reported in the literature. Studies of the fungous flora of soils in many parts of the world, however, have shown that a considerable number of species are widely distributed in soils, and it is believed that the more common soil organisms are included in the key. Wherever possible the key has been based on the existing keys to the various genera and species, making such changes as were necessary to in­ clude the soil forms and the new species described. In some cases it was necessary to key species which had not been examined in culture, which is rather difficult in instances where the published descriptions are meager. The key to the genera is adapted from that given in Engler and Prantl (18). The term "soil" is not defined. It is quite probable that the meaning of the term as used in some of the European literature differs somewhat from the common idea of soil in America, but it would be impossible to differentiate between them for the purposes of this paper. However, species of fungi were excluded from the key which are reported in the literature as having been isolated from material that had not been incorporated into the soil proper and was still recognizable, such as decayed wood and leaf mold. Such organisms are listed as doubtful soil fungi. A group of organisms which are probably soil inhabiting are many of the fleshy fungi, particularly members of the families Agaricaceae and Lycoperdaceae, which are found commonly in meadow soils and woodlands. The relationship between the mycelium of these fungi and their substratum is not sufficiently clear to definitely determine whether they should be classified as soil fungi or more properly as symbionts associated with the roots of various flowering plants in a mycorrhizal condition. It was there­ fore thought best to omit them from this list. Nor has any attempt been made to include those plant pathogenic fungi which are reported in the literature as occurring in the soil, but which have 225 226 J.C. GILMAN AND E. V. ABBOTI' been isolated :from the soil only by means of their attack on the particular host plant growing in soil infested by them. There is a considerable num­ ber of such organisms, particularly among the species of the genera Fusa­ rium and Pythium. Only such forms as have been directly isolated on an artificial cultural medium are included. It is recognized that in all work of this type the medium used exerted a selective action on the species reported; hence it should be noted that in the isolations made by the authors, Waksman and Fred's (54) synthetic acid agar was employed throughout. This agar is recommended for the isolation of fungi :from the soil be­ cause it eliminates bacterial colonies and favors the growth of fungi. For the cultural studies Czapek's solution agar and dextrose bean agar were used. A.s a rule morphological characters do not differ greatly on these media, although growth is usually more abundant on the bean agar. A. few organisms failed to grow at all typically on Czapek's agar. The soils studied in Iowa and Louisiana are described in previous pub­ lications (2), (3). The fungi reported :from Utah were isolated :from five representative types of cultivated soil :from that state, furnished through the courtesy of Dr. Thomas L. Martin, Brigham Young University, Provo, Utah. Two hundred and forty-two species of fungi in 61 genera have been described :from the soil. The following 20 species new to science are de­ scribed in this paper: Phoma humicola n.sp. Gliocladium atrum n.sp. Coniothyrium terricola n.sp. Sporotrichum pruinosum n.sp. Monilia implicata n.sp. Periconia lanata n.sp. Monilia brunnea n.sp. Acremoniella brevia, n.sp. Penicillium crateriforme n.sp. Dematium scabridum n.sp. Penicillium restrictum n.sp. Mesobotrys simplex n.sp. Penicillium guttulosum n.sp. H elminthosporium anomalum n.sp. Penicillium vinaceum n.sp. Spondylocladium australe n.sp. Gliocladium catenulatum n.sp. Acrothecium robustum n.sp. Gliocladium fimbriatum n.sp. Volutella piriformis n.sp. Cultures of these species have been deposited with the American Type Culture Collection, at .the John McCormick Institute for Infectious Dis­ eases at Chicago, Illinois. Twenty-six of the species described have not previously been reported :from the soil and 58 are reported :from new localities. The distribution of species amol\g the genera listed is worthy of com­ ment. Species of the genus Penicillium were most numerous, numbering 39; the genus Mucor was a close second with 32 species, Fusarium was third, being represented by 27 species, and A.spergillus was fourth, with 20 species. 'l'he other genera were represented by :from .one to six species each. KEY TO THE CLASSES, ORDERS, FAMILIES, AND GENERA OF SOIL FUNGI a. Filaments one-celled, rarely septate; conidia usually in sporangia; sex-. cells when present uniting to form resting-spores. A.. Phycomycetes. b. Conidia typically in globose to cylindric sporangia; zygosporous. I. Mucorales. A SUMMARY OF THE SOIL FUNGI 227 c. Sporangia always present, conidia sometimes present. d. Columella present; zygospore naked or with a few appendages. e. Wall of the sporangium homogeneous, not cuticularized, difflu­ ent. f. Sporangia similar. I. M ucoraceae p. 234. g. Sporangia pyriform. 1. Absidia. gg. Sporangia spherical. h. Sporangiophores united into groups on a rhizoidiferous stolon. Sporangiophores at the nodes opposite the rhi­ zoids. Spores usually longitudinally striate. 2. Rhizopus. hh. Sporangiophores emerging singly from the mycelium, not from rhizoidiferous stolons. Spores generally smooth, without longitudinal striae. i. Zygospores, the result of the union of two equal gametes. 3. :Jlucor. ii. Zygospores, the result of the union of two unequal gametes. 4. Zygorhynchus. ff. Sporangia of two sorts, primary and secondary. II. Thamnidiaceae p. 253. g. A single genus. 5. Thamnidium. ee. Wall cuticularized and persistent above, thin and diffiuent below. III. Pilobolaceae p. 253. f. A single genus. 6. Pilaira. dd. Columella absent; zygospore enveloped in a dense covering. IV. Mortierellaceae p. 254. e. A single genus. 7. Mortierella. cc. Sporangia rarely present, conidia always present. d. Conidia solitary; zygospore arising directly from the gametes. V. Chaetocladiacea p. 256. e. A single genus. 8. Cunninghamella. bb. Conidia single or in chains on conidiophores; sporangia when present give rise to zoospores ; oosporous. II. Peronosporales. c. Vegetative mycelium very narrow. uniform, much branched; spo­ rangiophores not distinct from mycelium; zoosporangia or conidia single on the tips of the branchlets, producing zoospores or a ger­ minating tube; oospores globose with a well developed outer wall. d. Conidia elongate, globose or lemon-shaped; contents escaping in- r' :228 J.C. GILMAN AND E. V. ABBOTI' to a globose vesicle in which the zoospores arise, zoospores 2- ciliate. VI. Pythiaceae p. 257. e. A single genus. 9. Pythium. ;aa. Filaments septate; conidia borne on conidiophores, sex-cells rarely in evidence. · b. Spores in a definite number in a sac: as ascospores. B. Ascomycetes. c. Asci in a perithecium; perithecium dark-colored, either without a stroma, partly seated in a loose mass of mycelium, or sessile above an imperfect stroma. III. Sphaeriales. d. Walls of perithecia thin and membranous, asci soon disappearing. e. Perithecia always superficial, with mouth surrounded by long, branched, hooked or spiral setae. VII. Chaetomiaceae p. 261. f. A single genus. 10. Chaetomium. ee. Perithecia usually sunken, with only short hairs about the mouth. VIII. Sordariaceae p. 263. f. Stromata absent, spores simple. 11. Pleurage. ff. Stromata absent, spores 4- many celled.