THE ALGAE 



77 



Sexual Reproduction 



As has already been stated the sexual reproduction in Coleochaete is 

 Gogamous and shows an alternation of generations (Fig. 59). In fact it is 



ANTHERIDIUM 



O^ NUCLEU^S 

 $ NUCLEUS 



Fig. 59. — Coleochaete pulvinata. A, Young zoosporangium. B and C, Antheridial branch, 

 with young oogonium. D, Oogonium shortly before the opening of the trichogyne. 

 E, Oogonium after opening. F, Binucleate zygote. G, Enlarged oogonium with 

 encircling filaments. H, Germination of the resting zygote (oospore). {After Oltmanns.) 



the onlv example of a non-homologous alternation of generations in the 

 Chlorophyceae, that is to say, an alternation in which the two generations are 

 morphologically different. Sexual reproduction usually occurs from IVIay 

 to July. 



The antheridia are developed in clusters at the ends of the vertically 

 growing branches, frequently on the same branches that bear the oogonia. 



