The fern prothallus is:

$A$: Events precursor to the seed habit are seen in some members of pteridophytes.
$R$: Development of the zygotes into young embryos takes place within the female gametophyte.

$Selaginella$ is characterized by the presence of:

$Anabaena$ is associated with the .......... of $Azolla$.

Which of the following is a heterosporous fern?

In $Lycopodium$,the antherozoids are .......