Ferns are characterised by

Which of the following organisms fell to form coal deposits?

$Selaginella$ is heterosporous. It produces two types of spores. The microspore develops into microgametophyte and the megaspore develops into megagametophyte. With respect to gametophyte,which one statement is correct?

The stele in the rachis of $Pteris$ is

In $Dryopteris$ (fern),the permanent roots are .........

Assertion $(A)$: $Selaginella$ is heterosporous.
Reason $(R)$: The strobili of $Selaginella$ are unisexual.