In order to prove the identity of the species, in the spring of 1908 a pile of dead grass and leaves was raked together on the ground and burned, giving rise to a burnt place similar to those on which Pyronema omphalodes (Bull.) Fuckel was known to occur. As soon as the first rain occurred after the burning of this material a few of the plants from the laboratory were placed in the ashes and on the ground where the fire had been. In about ten days a good growth of Pyronema omphalodes (Bull.) Fuckel was found, the plants occurring in confluent masses as usual. These plants were taken into the laboratory and inoculations made from them on heated-soil. These at once produced mycelium radiating out from the point of infection and later produced an abundance of fruit, the ascocarps being scattered as is usually the case in laboratory grown material. Some of the laboratory plants show rather well developed, hyaline, septate hairs, although these are not a conspicuous character. The color also varies much from bright rose or salmon to almost white. The paler plants are usually those produced on less favorable substrata. The fungus has doubtless been described under several names. SUMMARY 1. Contrary to the statement of Kasaroff, our experiments have failed to show the presence of a soluble, toxic substance in unheated-soil which will retard the growth of Pyronema when applied to heated-soil. 2. Heating the soil to a high temperature brings about chemical changes indicated by the following: (a) The extract of heatedsoil is of a bright amber or reddish-brown color and possesses a characteristic odor while the extract of unheated-soil is colorless and almost odorless, (b) the amount of soluble material in the extract of heated-soil is increased to approximately six to ten times that of the extract of the same soil unheated. 3. The materials rendered available by the heating of the soil serve as food for Pyronema, as is indicated by the following: (a) The conditions necessary for the production of a highly colored extract in soil are the conditions most favorable to the growth *The exact increase will vary with the soil and manner in which it is treated, temperature, length of time heated, etc. of Pyronema, (b) the extract of heated-soil is itself so favorable as a culture medium that it is at once attacked by the fungus while the extract of the same soil unheated remains uninfected, (c) heated-soil watered with the extract of another heated-soil is much more favorable to Pyronema growth than similar soil watered with distilled water, the former producing mycelium and fruit in much greater abundance. 4. Distillation of heated-soil extract does not remove the properties favorable to Pyronema, both the colorless distillate and the highly colored distillation residue being favorable to its growth, the distillation residue, however, appearing to be more favorable than the distillate. 5. Excessive heating of soil in a combustion-tube renders it unfavorable to Pyronema growth. The distillate has a very offensive odor but is apparently neutral to Pyronema growth when applied to heated-soil. 6. It has been impossible to render unheated-soil favorable to the growth of the fungus by the introduction of the extract of heated-soil, this being apparently due to the fact that the nutrient materials in the extract are rendered insoluble by the action of unheated-soil. 7. Not only is the extract of heated-soil a favorable nutrient medium for Pyronema, but for other fungi as well, indicated by the fact that the extract is attacked by fungi of various kinds. 8. Soil subjected to steam or dry heat (either in a closed oven or by burning over the surface of the soil), becomes a very favorable nutrient medium for fungi of various kinds, by reason of the large quantity of food material rendered available through the heating of the materials in the soil. We wish to acknowledge our indebtedness to Dr. W. J. Gies, of the Department of Biological Chemistry of Columbia University and Consulting Chemist to the New York Botanical Garden, for his oversight and aid throughout the course of the present work. We also extend thanks to Dr. Oswald Schreiner, of the Bureau of Soils, Washington, for numerous suggestions on various questions which have arisen pertaining to matters of soil fertility. FRED J. SEAVER, NEW YORK BOTANICAL GARDEN. THE NORTH AMERICAN MUCORALES-I Family MUCORACEAE DAVID ROSS SUMSTINE INTRODUCTION The Mucoraceae have attracted the attention of botanists for more than two hundred years and from the number of papers and theses published on the subject in Europe recently the interest remains unabated. The American species have never been studied systematically, although local and state lists of fungi contain the names of the more common species. Pound* describes the American genera and enumerates a few species. The splendid work of Blakesleet deals entirely with zygospore formation. The synonymy is exceedingly complicated and the status of many described species cannot be definitely determined. Lendner reports seventeen imperfectly described species in the genus Mucor appearing from 1884 to 1906. The rule of priority has frequently been ignored and the same name has been used for different species. Fischer§ has unraveled the intricate synonymy of the European species. Dried specimens soon lose their taxonomic characters, and therefore herbarium material, even when available, is seldom satisfactory for the exact determination of the specimens. The viability of the spores is lost in three to ten months and consequently cultures cannot be made from old material in order to establish the true identity of the specimens. While this paper is intended primarily to enumerate only species seen and examined by the writer, yet, for the purpose of giving a better survey of the American species, a few have been admitted on the authority cited under Species Reported. At the conclusion of these studies, my own material will be placed in the Carnegie Museum, Pittsburgh, and in the New York Botanical Garden. This will be done in the hope that other mycological workers who are not directly connected with large public institutions will also deposit their material in institutions where it will be available to future students. I am indebted to Dr. W. J. Holland, of the Carnegie Museum, Pittsburgh, for assistance in making collecting trips in Pennsylvania. My thanks are especially due to Dr. N. L. Britton for the opportunity of examining the specimens in the herbarium and consulting the literature in the library of the New York Botanical Garden. The various members of the staff of the Garden have very kindly and cheerfully rendered valuable service in the preparation of this paper. Order MucORALES Saprophytic or parasitic fungi with well-developed mycelium, the mycelium branched and unicellular. Reproduction sexual (zygospores) and asexual (spores produced in sporangia or conidia produced singly or in chains). Schroeter* recognizes five families, Mucoraceae, Mortierellaceae, Choanophoraceae, Chaetocladiaceae, and Piptocephalidaceae. The total number of species for the whole world is less than 150. Most of these are described from Europe. Family MUCORACEAE Asexual reproduction by spores in sporangia with columella or sometimes in sporangioles without columella. Sexual reproduction by zygospores formed on the mycelium or on aerial filaments by the union of two copulating branches (gametes). KEY TO THE GENERA 1. Simplices Sporangiophores simple, unbranched. Sporangiophores arising from stolons, sporangial Sporangiophores arising from the nodes of Sporangiophores arising from the internodes of the stolons. * Pflanzenfamilien 1': 123. 1892. 1. MUCOR. 2. ABSIDIA. Sporangiophores variously branched. Sporangiophores dichotomously branched. Sporangiophores without terminal sporangia, Sporangiophores with terminal sporangia, branches with sporangioles. Sporangioles on dichotomous branches. Sporangioles on straight branches, arising Sporangiophores with sporangia only. Branches long or short, zygospores with nearly Branches as above, zygospores on dichotomous 8. SYZYGITES. 9. CIRCINELLA. 10. THAMNIDIUM. 12. HELICOSTYLUM. 11. BULBOTHAMNIDIUM. 13. CALYPTROMYCES. 14. ZYGORHYNCHUS. 1. MUCOR (Mich.) L., Sp. Pl. 1185. 1753 › Ascophora Tode, Fung. Meckl. 1: 13. 1790. Type species, Ascophora Mucedo Tode. Rhizopus Ehrenb. Nov. Acta Acad. Leopold 101: 198. 1820. Type species, Rhizopus nigricans Ehrenb. ORIGINAL DESCRIPTION: Fungus vesicula subrotunda, in qua semina numerosa affixa, receptaculis criniformibus constans. Type species, Mucor Mucedo L. Sporangiophores simple, usually growing in clusters of two, three, or five from the nodes of the stolons, enlarged below the sporangia forming an apophysis; mycelium white at first, then brown, growing by stolons attached at different places to the substratum by rhizoids; zygospores borne on the mycelium, naked. |