Pteridophytes are also known as

Apical growth of the lower vascular plants takes place by an apical cell. This cell is generally pyramidal. Though four-sided in shape,it is often referred to as a three-sided cell because

$Selaginella$ 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 first vascular plants are:

The gametophyte of pteridophytes requires to grow$-$

How many classes does the division Pteridophyta contain?