5o6 



General Botany 



pollen tubes have enlarged downward into this cavity. Finally 

 two free-swimming sperms are liberated from each tube into the 



C J . Chamherlait 



Fig. 314. Fertilization in a cycad {Diodn), showing pollen tubes in the nucellus ; 

 the spirally ciliated sperms ; and two archegonia, one (right) with egg, the other 

 (left) after union of sperm and egg nucleus. Surrounding the archegonia is 

 the female prothallus. 



pollen chamber. The sperms are relatively very large (.2 to 

 .3 mm.) and are propelled by a much-coiled spiral line of cilia 

 (Fig. 314). The pollen chamber at this time contains the liquid 

 discharged from the pollen tubes, and in this liquid the sperms 

 swim about. 



