Central threads of the bundle are closely packed, but free. Threads divide into short angular cells which separate and become æcidiospores, with orange-colored content.
Æcidiospores carried by the wind to wheat, oats, grasses, etc. Here they germinate, mycelium enters at stomate, and forms mycelium between cells of the host.
Uredo stage (red-rust) on wheat, oats, grasses, etc.
Mycelium between cells of host.
Bears uredospores (1-celled) in masses under epidermis, which is later ruptured and uredospores set free.
Uredospores carried by wind to other individual hosts, and new crops of uredospores formed.
Teleutospore stage (black rust), also on wheat, etc.
Mycelium between cells of host.
Bears teleutospores (2-celled) in masses (sori) under epidermis, which is later ruptured.
Teleutospores rest during winter. In spring each cell germinates and produces a promycelium, a short thread, divided into four cells.