Question

Thallophyta, bryophyta, and pteridophyta are called as 'cryptogams'. Gymnosperms and angiosperms are called as 'phanerogams'. discuss why?

Answer 1

Cryptogamae (Crypto= hidden Gamae= marriage) means Plants that do not bear seeds.
Thallophytes, Bryophytes and Pteridophytes reproduce mostly by seed like structures called Spores. Thus they do not produce seeds. Hence they are Cryptogams.

Phanerogamae (Phanero= visible Gamae=Marriage) are the seed bearing plants.
Gymnosperms and Angiosperms continue their generation by structures called seeds. Hence they are Phanerogams.

Answer 2

Gymnosperms and angiosperms are called as "phanerogams" due to following reasons :
1.reproductive organs are seen outside
2.seeds may be enclosed or exposed
3.if seeds are enclosed - angiosperms 
4.if seeds are exposed - gymnosperms

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