Heterospory is an event in which two different types of spores i.e microspore and megaspore are produced by the plant.
The microspore develops into male gametophyte whereas megaspores develop into female gametophyte.
Male gametophyte releases male gamete which fuses with female gamete formed by female gametophyte.
After fusion of gametes, zygote is formed.
Zygote develops inside the female gametophyte.
The preservation and development of megaspore inside the female gametophyte, guarantees right development of zygote.
Later on, zygote develops into sporophyte.
The development of seed practice is associated with the preservation of the megaspores inside the megasporangium or female gametophyte.
Therefore, heterospory is very important from an evolutionary point of view as it is the ancestor of the seed pattern.
Examples :- Pinus , Cycas etc.
