Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. The male gametophyte releases the male gametes and these reach the female gametophyte to fuse with the egg. The development of the zygote takes place inside the female gametophyte.
E.g., Salvinia and Selaginella produces two kinds of spores
(i) macrospores: these are large in size,
(ii) microspores : these are small in size. These pteridophytes are heterosporous.
Significance:
(a) The mega and microspores germinate and then give rise to male and female gametophytes.
(b) The female gametophyte is retained on parent sporophyte for variable period of time.
(c) The development of zygote into young embryo occurs within female gametophyte.
