FILAMENTOUS GREEN ALG^E 



247 



of small motile gametes, or of special gametes, the sperms and 

 eggs formed respectively in sperm cases (antheridia) and egg 

 cases (oogonia). 



381. The green felts (Vaucheria). The " green felts" are 

 good examples of the siphon algae. They occur in fresh-water 



Fig. 196. 



Vaucheria sessilis; oogonium opening and emitting a bit of protoplasm; sperms; sperms 

 entering oogonium. (After Pringsheim and Goebel.) 



ponds, lakes, streams, or on damp soil. The threads are long, 

 branched, and continuous, that is without cross walls except where 

 reproductive organs or cells are formed. The plants usually 

 form dense mats of a coarse consistency and are known as "green 

 felts," because of the felted consistency of the mats. Asexual 



Fig. 197. 



Fertilization in Vaucheria. mn, male nucleus; /, female nucleus, 

 the egg and approaching the female nucleus. (After Oltmanns.) 



Male nucleus entering 



reproduction is by large spores formed from the protoplasm in 

 the ends of the threads separated by a cross wall. Some of these 

 spores are motile, with numerous pairs of cilia over the surface, 

 while others are non-motile. These spores escape from the 

 enclosing cell wall. In sexual reproduction specialized short 



