Question:
The heterosporous pteridophytes show certain characteristics, which are the precursor to the seed habit in gymnosperms. Explain.
Solution:
Genera like selaginella, Sylvania, Marsilea etc produces two kinds of spores. Micro and macrospores which are known as heterosporous.
(i) Evolutionary heterospory
(ii) In-situ development of the embryo within the female gametophyte.
(iii) The decrease in the number of megaspore to one.