Answer:
Seed habit The
differentiation of spores into microspores and megaspores and their dependence
on the parent saprophyte for the nutrition, are the certain features in the
lifecycle of Selagineila, which have been considered as the essential
pre-requite for formation of seed, the characteristic of spermatophyte.
The evolution of
heterospory and seed habits in Selagineila is evident by the following characters
(i) Reduction
to a single functional megaspore per sporangium.
(ii) Retention
and germination of megaspore within megasporangium
(iii) Development
of protective layer and nutritive tissue called tapetum is present.
(iv) Development
of embryo sac with in the sporangium.
(v) Modification
of distal end of mega sporangium to capture pollen grain.
(vi) Pollination
and siphonogamy.
(viii) Temporary
suspension of growth of embryo (dormancy period).
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