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 



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 



