zoosporangium

When the free ends of the hyphae emerge again into the air they swell up into spherical bodies which may either fall off and behave as conidia, each putting out a germ-tube and infecting the host; or the germ-tube itself swells up into a zoosporangium which develops a number of zoospores.

Motile zoospores which escape from the zoosporangium are present except in Aplanes.

Each “conidium” contains numerous nuclei and is really a zoosporangium, as after dispersal it breaks up into a number of zoospores.

The oospore on germination usually gives origin to a zoosporangium, but may form directly a germ tube which infects the host.

B, a ripe zoösporangium, × 100.