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).
The teleutospore, with the sporidia which arise from it, is always present, and the division into genera is based chiefly on vulgaris, with a, aecidium fruits, p, peridium, and sp, spermogonia.
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.
Before the teleutospore reaches maturity the nuclei fuse, and the uninucleate condition Q C then continues again until aeci dium formation.
There is also a further reduction in that the basidium is not derived from a teleutospore but is borne directly on the mycelium.