The sperm of fern is

Select the incorrect statement regarding the prothallus of Pteridophytes:

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

They possess roots,stems,and leaves.

The ferns in which the entire sporangium develops from a single superficial cell of the sporophyll are known as

How many classes does the division Pteridophyta contain?