BASIDIOMYCETES. The Basidiomycetes (mush rooms, toadstools, etc.) are a remarkable class. There is no trace of sexuality in the group, not even the vestiges of sexual organs which generally remain even when plants reproduce without them. Apart from certain peculiar phenomena of fusing nuclei, there are no dews to the problem of the origin of the group. The diverse orders are held together by a phase common to all the life his tories, namely, the basidium, which is the swollen tip of a filament bearing spores on slender branches. It has been found that this basidium of the toadstools and the puffballs is represented by the promycelium of the smuts (Ustilaginales, q.v.) and rusts (Uredinales, q.v.). This promy celium arises from the winter spore (teleuto spore), which is essentially only a resting spore to tide the parasite over an unfavorable season.
There are kinds of rusts (Leptopuccinia) in which the teleutospores form promycelia directly upon the host plant, and these conditions resemble strikingly the basidia of certain toadstool forms. The winter spore (teleutospore) of the rusts and the smuts is then merely an adaptation related to the parasitic habit, and unnecessary for sapro phytes such as the toadstools, bracket fungi, and puffballs, It must not be supposed, however, that there is only one conspicuous line of development among the Basidiomycetes, for there are several divergent lines, prominent among which are the rusts (liredinales), smuts (Ustilaginales), and certain orders of the toadstools (Hymenomy cetes), and puffballs (Gasteromycetes). The re lation of the Basidiomycetes to the other groups of fungi is problematical.