VAUCHERIA. 



IO7 



251. Sexual organs of vaucheria. Antheridium. — The 



antheridia are short, slender, curved branches from a main 

 thread. A 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. 108. The protoplasm in 



Vaucheria sessilis, one antheridium between two oogonia. 



the antheridium forms numerous small oval bodies each with two 

 slender lashes, the cilia. When these are formed the antherid- 

 ium opens at the end and they escape. It is after the escape 

 of these spermatozoids that the antheridium is collapsed. Each 

 spermatozoid is a male gamete. 



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

 they become large and , > 



somewhat oval. The / J 



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 oogonium, 

 as shown in the figure, is 

 usually turned somewhat 

 to one side. When mature the pointed end opens and a bit of the 

 protoplasm escapes. The remaining protoplasm forms the large 

 rounded egg cell which fills the wall of the oogonium. In some 

 of the oogonia which we examine this egg is surrounded by a 

 thick brown wall, with starchy and oily contents. This is the 



Fig. 109. 

 Vaucheria sessilis ; oogonium opening and emit- 

 ting a bit of protoplasm; spermatozoids ; sperma- 

 tozoids entering oogonium. (After Pringsheim and 

 Goebel.) 



