In brachy and hemi the aecidiospores are absent, the mycelium from the sporidia giving origin directly to the uredospores; the former possess spermatia, in the latter they are absent.
The gelatinous, generally reddish-brown masses of spores - the teleutospores - formed on the juniper in the spring germinate and form minute spores - sporidia - which give rise to the aecidium stage on the pear.
In lepto and micro forms both aecidiospores and uredospores are absent, the sporidia producing a mycelium which gives rise directly to teleutospores; in the lepto forms the teleutospores can germinate directly, in the micro forms only after a period of rest.
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.
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.
D, The sporidia: in B the sporidia have coalesced in pairs at v.
When the sporidia infect a plant the mycelium so produced gives origin to aecidiospores and spermatia; the aecidiospores on infection produce a mycelium which bears uredospores and later teleutospores.