Peronosporales

Peronosporales form an internal parasitic mycelium within a host plant. In different structures conidia are formed. They germinate while forming motile spores that than reinfect a host plant. Within the host plant by sexual means, after fertilisation of an oogonium, thick-walled oospores are formed that enable hibernation. The oospores germinate and form similar motile spores as just mentioned. The ornamentation of the oospore wall often is an important diagnostic character.