368 



THE NON-VASCULAR PLANTS 



properly be called spores; cells which reproduce directly 

 are spores, and cannot properly be called gametes. Thus 



the fertilized egg is properly 

 called a spore; a sex process 

 is responsible for its origin, 

 but it is not a sex cell itself ; 

 only gametes are sex cells. 



In Ulothrix we have the 

 appearance of sex, but we do 

 not have its differentiation; 

 that is to say, although the 

 sex act is performed, there 

 appears to be no difference 

 between the gametes, no dif- 

 ferentiation into male and 

 female. But in (Edogonium, 

 another common fresh-water 

 alga, we have distinct male 

 and female gametes. (See 

 Figure 165.) In this form 

 certain cells become enlarged 



Fig. 165. — (Edogonium. A, a young , , , rni j i i 



filament. B, portion of a mature ^nd rOUnded. The protopkst 



filament. The largest cell is an is transformed into an egg. 



Other vegetative cells subdi- 



o'dgonium, that Is, a cell which con- 

 tains an egg. The oflgonium of this 



plant contains just one large egg vidc iuto Smaller Cells and 



wUch is richly supplied with food, jhese producc spcrms. The 



indicated by the numerous light , 



oval bodies. Near the bottom of spcrms escapc into the water. 



this picture are three rafendia (cells They swim actively and ap- 



which produce sperms). From two , j i. 



of these antheridia sperms have es- P^ar tO be attracted tO the 



caped. A third sperm, without its egg. Presently One of them 



cilia, may be noted at the bottom , i .1 i r ,•!• 



of the oogonium. It has reached reaches the egg and fertihzes 



the egg and is about to fuse with it, it. The Cell which produceS 



