22 HEREDITY AND EVOLUTION IN PLANTS 



and is usually slightly curved, while the remainder, the 

 -venter, is imbedded in the tissue of the cushion. As the 

 archegonium approaches maturity it is seen to contain 

 three cells; a long neck-canal cell, nearly filling the neck, 

 an egg-cell or ovum, filling the venter, and between these 

 two a ventral-canal cell. The egg is the female reproduc- 

 tive cell. As it matures, the other two cells become disin- 

 tegrated into a mucilaginous mass that fills the neck-canal. 

 Since the archegonia contain the eggs they are the female 

 reproductive organs. 



FIG. 22,-r-Portion of a cross-section of a prothallus of a fern (Adian- 

 tum), showing an antheridium (an), and sporogenous cells within. 

 (Drawn from preparation of E. W. Olive.) 



15. Reproductive Organs : Antheridia. Search among 

 the rhizoids will reveal another class of organs, the an- 

 theridia, globular and also having walls only one cell 

 thick. These are the male reproductive organs. At 

 maturity they contain a large number of tiny motile cells, 

 composed chiefly of a coiled nucleus, and able to swim 

 about in water by the vigorous lashing of numerous little 

 thread-like cilia attached to one end. These are the 

 sperms, or male reproductive cells (Figs. 22 and 23.) 



