FILAMENTOUS GREEN ALG^E 



245 



In sexual reproduction sperm cases are formed in groups of 

 four, each one producing a small biciliate sperm. The egg cases 



Fig. 189. 

 Stem of 

 aquatic plant, 

 showing Co- 

 1 eoc hast e, 

 natural size. 



Fig. 190. 

 Thallus of Coleochaete scutata. 



(oogonia) are large and possess a long slender beak called a 

 trichogyne. The sperm becomes attached to the trichogyne; its 



Fig. 191. 



Portion of thallus of Coleo- 

 chaete scutata, showing empty 

 cells from which zob'spores 

 have escaped, one from each 

 cell; zobspores at the left. 

 (After Pringsheim.) 



Fig. 192. 



Portion of thallus of Coleo- 

 chaste scutata, showing four 

 anlheridia formed from one 

 thallus cell; a single sperm 

 at the right. (After Prings- 

 heim.) 



nucleus moves down the tube, enters the egg and fuses with the 

 nucleus of the egg. The egg after fertilization becomes sur- 



