What is heterospory? Briefly comment on its significance. Give two examples.
Genera like Selaginella and Salvinia which produce two kinds of spores macro and microspores are known as heterosporous. The megaspore and microspores germinate and give rise to female and male gametophytes, respectively. The female gametophytes in these plants are retained on the parent sporophyte for variable periods. The development of the zygotes into young embryo takes place within the female gametophytes. This event is considered as an important step in evolution leading to seed habit. Heterospory is considered as the first step towards seed habit. Selaginella and Marsilea, show seed habit.
