122 



BOTANY. 



207. Vaucheria sessilis; the sessile vaucheria. — In this 

 plant the sexual organs are sessile, that is they are not borne 



on. a stalk as in some other 

 species. The sexual organs 

 usually occur several in a 

 group. Fig. 96 represents 

 a portion of a fruiting 

 plant. 



208. Sexual organs of 

 vaucheria. Antheridium. 

 — The antheridia are]short, 

 slender, curved branches 



Fig. 96. 



Young antheridium and oogonium of Vaucheria , , . , t 



sessilis, before separation from contents of thread by from a main thread. A 



a sep um. septum is formed which 



separates an end portion from the stalk. This end cell is the 

 antheridium. Frequently it is collapsed or empty as shown in 

 fig. 97. The protoplasm in the antheridium forms numerous 

 small oval bodies each with two slender lashes, the cilia. When 

 these are formed the antheridium opens at the end and they 



Fig. 97. 

 Vaucheria sessilis, one antheridium between two oogonia. 



escape. It is after the escape of these spermatozoids that the 

 antheridium is collapsed. Each spermatozoid is a male gamete. 

 209. Oogonium. — The oogonia are short branches also, but 

 they become large and somewhat oval. The septum which 

 separates the protoplasm from that of the main thread is as we 

 see near the junction of the branch with the main thread. The 



