After fertilization the female cell, now called the oospore, divides and part of it develops into the embryo (new sporophyte), which remains dormant for a time still protected by the ovule which has developed to become the seed.
The fertilized egg-cell (oospore) forms a filamentous structure, the proernbryo, from a restricted basal portion of which one or more embryos develop, one only as a rule reaching maturity.
Whether a spore results from the sexual union of two similar gametes (zygospore) or from the fertilization of an egg-cell by the protoplasm of a male organ (oospore); or is developed asexually as a motile (zoospore) or a quiescent body cut off from a hypha (conidium) or developed along its course (oidium or chlamydospore), or in its protoplasm (endospore), are matters of importance which have their uses in the classification and terminology of spores, though in many respects they are largely of academic interest.
The oospore on germination usually gives origin A ?°.
Oogonium and development of the oospore in Peronospora.