The Cytology of Eocronartium Muscicola

The view of Brefeld (5) that the promycelium of the Uredinales and Ustilaginales is homologous with the transversely septate basidium of the Auriculariales has received general acceptance.His theory, based on a morphological study of the two structures, has been substantiated by the results of subsequent cytological investigations on members of these three groups and of the higher Basidiomycetes.Consequently the Auriculariales are regarded as closely related to the Uredinales, and as probably intermediate in origin between them and the higher Hymenomycetes.Comparatively little is known, however, concerning the nuclear history and general cytology of members of this order.Only species of the genus Auricularia have been examined, and here the facts are only partially determined.The investigation of members of other genera is therefore desirable, and should shed further light on the phylogeny of the Basidiomycetes.A preliminary examination of stained sections of the sporophore of Eocronartium muscicola (Fries) Fitzpatrick, made in connection with the writer's (12) study of the parasitism of this species, disclosed the fact that unusually large nuclei make this form a favorable subject for cytological investigation.The present paper is an outgrowth of this discovery, and embodies the results of an investigation of the cytology of this species conducted during the past three years. MATERIALS AND METHODSEocronarttum muscicola is an obligate parasite occurring on a considerable number of mosses of various genera.It produces small Typhula-like sporophores at the apices of the branches of the moss gametophore, in which it exists as a perennial, intracellular parasite.