3 68 



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 

 and rounded. The protoplast 



Fig. 165. — (Edogonium. A, a young 

 filament. B, portion of a mature 



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



osmium, that is, a cell which ^con- Qthej . ve g e tative Cells Subdi- 

 tains an egg. The oogonium of this ° 



vide into smaller cells and 



The 



these produce sperms. 



egg. Trie oogonium i 

 plant contains just one large egg 

 which is richly supplied with food, 

 indicated by the numerous light 



oval bodies. Near the bottom of sperms escape into the water. 



this picture are three antkeridia (cells They Swim actively and ap- 

 which produce sperms). From two , , , 



of these antheridia sperms have es- P ear to be attracted to the 



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



cilia, may be noted at the bottom i ■•. j r .m- 



of the oogonium. It has reached reacheS the e SS and fertilizes 



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



