274 Introduction to Botany. 



grow out over its surface. Soon it comes to rest and 

 organizes a wall over its surface, and after a brief period 

 it germinates, producing a new branched filament, with an 

 expansion at one end for anchorage to the substratum. 



In the sexual method of reproduction, two forms of out- 

 growths are produced on the same filament ; a rounded 



FIG. 138. 



Vaucheria sessilis. i, a filament-bearing oogonia (c) and an Antheridium (d). 

 The rounded portion to the left represents the spore from which the filament 

 has sprung. The clear branched portion is a clinging organ by which anchor- 

 age is made with the substratum. 2, a germinating spore. 3, a later stage. 

 4, an asexual spore escaping from its parent cell. 5, the same after it has come 

 to rest and surrounded itself with a cell wall. 6, the spore, (5) in the first stage 

 of germination ; 2 and 3 are later stages. After SACHS. 



one (the oogonium), which is separated from the parent 

 filament by a wall, and contains the egg, and . a slender 

 outgrowth (the antheridium\ containing the sperms at its 

 apical portion (see Fig. 138). The cells containing the 

 egg and those containing the sperms break open at their 

 apices, and the sperms swim out by means of two cilia 



