48 VAUCHERIA SESSILIS. 



II. REPRODUCTIVE CHARACTERS. 



1. Asexual reproduction. 



At the tips of some branches search for the following stages: 



a. Where there has been formed a transverse partition- 

 wall. 



b. Where the protoplasm thus enclosed is becoming 

 spherical in form. 



c. Where this large mass of protoplasm, which is a com- 

 pound zoospore, is escaping from its enclosing walls. 



d. Search for free zoospores and observe the movements. 

 Around the margin of the dish, or held by the older plants 



if the material has been kept for a few days, may be found 

 specimens which when mounted will show: 



e. Young plants beginning to grow from zoospores. 

 /. Draw. 



2. Sexual Reproduction. 



On the side of filaments may frequently be seen some 

 branches of one or two kinds, as follows: 



a. The oogonium, an oval body with a beak-like tip, con- 

 taining an oosphere, the female gamete, or sex spore, 

 the oospore. 



b. Arising from the filament near the base of the oogonium 

 is the antheridium, 1 an elongated and coiled body. 



c. Note how the structures are adapted to aid in the union 

 of the passive egg of the oogonium and the motile sperm 

 from the antheridium. 



d. Observe the very heavy wall about the oospore or fer- 

 tilized egg. Of what significance is this? 



e. Draw oogonia, antheridia, and oospores. 



1 In V. sessilis the antheridial stalk arises as a separate branch from 

 the plant body, while in other species, e.g. V. geminata, the anther- 

 idial stalk is the termination of a branch on the side of which one or 

 more oogonia may be borne. 



