Life-history in some cases very complex and with well-marked sexual process and alternation of generations, in others much reduced; basidium (promycelium) derived usually from a thick-walled spore (teleutospore).
Brefeld regarded the promycelium as a kind of basidium, bearing lateral or terminal conidia (comparable to basidiospores), but since the number of basidiospores is not fixed, and the basidium has not yet assumed very definite morphological characters, Brefeld termed the group Hemibasidii, and regarded them as a halfway stage in the evolution of the true Basidiomycetes from Ph co Y Y mycetes, the Tilletia type leading to the true basidium (Autobasidium), the Ustilago type to the proto pm basidium, with lateral spores; but this p m view is based on very poor evidence, so that it is best to place these forms?p, c;,::, as a separate group, the Ustilaginales.
The teleutospore puts forth on germination a fourcelled structure, the promycelium or basidium, and this bears later four sporidia or basidiospores, one on each cell.
Formerly, before the relationship of promycelium and basidium were understood, the Uredineae were considered as quite independent of the Basidiomycetes.
The first named contains a small number of forms with the basidium divided like the promycelium of the Uredineae.