238 PLANT LIFE 
enter into the details of their development, 
but we may note that each is a specialised 
cell—not only are the two gametes different 
from each other, but they are different from 
Aer 
es EEG 
Fig. 27.—I. Prothallus of fern; the lower surface, AB, indi- 
cates the direction in which the section shown in II is cut. 
II. Section through an antheridium (An) and archegonium 
(Arch) in which is situated the egg, E 
all the other cells of the prothallus. Each 
consists of a naked mass of nucleated proto- 
plasm, but while the sperm consists mainly 
of nucleus, the egg contains a very large 
amount of cell protoplasm. We do not as 
yet know exactly on what the definitely 
