The main plant body of $Selaginella$ $sp.$ is

In vascular cryptogams,the antherozoids and the egg cells mature at different times,which results in:

In $Selaginella$,when the sporophyte develops directly from the female gametophyte other than the oosphere,the condition is called:

Which of the following pteridophytes belongs to the class $Pteropsida$?

Which of the following is an aquatic and free-floating fern?

During fertilization in ferns,the male gamete reaches the female gamete through the agency of: