Question

why thallophyta,bryophyta and pterodophyta are called cryptogams?

Answer 1

The thallophyta , the  bryophytes and the pteridophytes have naked embryos that called spores.The reproductive organs of plants in all these three groups are very inconspicuous and they are called "cryptogamae" or those with hidden reproductive organs.

Answer 2

They are called crypto games because their reproductive organs are hidden or absent