112 



MORPHOLOG Y. 



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

 body, fig. 114. After swimming around for a time they come to rest, ger- 

 minate, and produce another plant. 



261. 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. 116. 



Coleoch^ete soluta ; at left branch bearing oogonium (oog)\ antheridia (nnt); 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. 116). Several oogonia are formed on 



one plant, and in such a 



plant as C. scutata they are 



formed in cl ring near the 



margin of the disk. 



262. Antheridia. — In C. 



scutata certain of the cells 



of the plant divide into four 



smaller cells, and each one 



of these becomes an antheri- 



sporocarp ruptured by<ii"™- I" C. soluta the an- 

 growth of egg to form cell theridia grow out from the 

 mass. Cells of this sporo- , , .,,,., 



phyte forming zoospores. end oi terminal cells m the 



7, it8, C. scutata. : form c.f short flasks, some- 



times four in number or less (fig. 116). A single spermatozoid is formed 

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



Fig. 117. 

 Two sporocarps still 

 surrounded by thallus. 

 Thallus finally decays and 

 sets sporocarp free. 

 Figs. 



Fig. 

 Sporocarp ruptured 



