COLEOCH&TE. 



'55 



form a single zoogonidium which has two cilia at the smaller end of the oval 

 body, fig. 157. After swimming around for a time they come to rest, ger- 

 minate, and produce another plant. 



327. Sexual reproduction. Oogonium. The oogonium is formed by the 

 enlargement of a cell at the end of one of the threads, and then the end of the 



Oog ; 



Fig. 159. 



Coleochaete soluta; at left branch bearing oogonium (oog) ; antheridia (<mt); egg in 

 oogonium and surrounded by enveloping threads ; at center three antheridia open, and one 

 spermatozoid ; at right sporocarp, mature egg inside sporocarp wall. 



cell elongates into a slender tube which opens at the end to form a channel 

 through which the spermatozoid may pass down to the egg. The egg is 

 formed of the contents of the cell (fig. 159). Several oogonia are formed on 



one plant, and in such a 

 plant as C. scutata they are 

 formed in a ring near the 

 margin of the disk. 



328. Antheridia. In C. 

 scutata certain of the cells 

 of the plant divide into four 

 smaller cells, and each one 

 of these becomes an antheri- 

 dium. In C. soluta the an- 



w IP 



Fig.i6o. 



Fig. 161. 



Two sporocarps still Sporocarp ruptured by " 

 surrounded by thallus. growth of egg to form cell theridia grow out from the 

 Thallus finally decays and mass. Cells of this sporo- . , ,. . ,, 



sets sporocarp free. phyte forming zoospores. end O terminal cells in the 



Figs. 1 60, 1 6 i.C. scutata. form of short flasks, some- 



times four in number or less (fig. 159). A single spermatozoid is formed 

 from the contents. It is oval and possesses two long cilia. After swim- 



