Define/Explain: Heterosporous.

(N/A) Heterospory is a condition in plants where two different types of spores are produced,which differ in size and function.
These are known as microspores (small,male) and megaspores (large,female).
This phenomenon is observed in some pteridophytes like $Selaginella$ and $Salvinia$,and in all seed-bearing plants (gymnosperms and angiosperms).