CaHLOBLASTEu^. 



353 



oosphere immediately begins to secrete a wall of cellulose 

 about itself, and it thus becomes an oospore {F, Fig. 170). 

 According to Pringsheim, the oospore remains for three 

 months in a resting state before germinating ; in the latter 

 process the out&r coat of the spore splits, and through the 

 opening a tube grows out which eventually assumes the form 

 and dimensions of the full-grown plant. 



Fig. 170.— Sexual ortrana of Yaucheria sessilis. A, beE:inning of the formation of 

 tlie oogonium (orf) and antherifiinm (A) upon tiie branch b, S, later Biage of the 

 same, the antheridium (a) now separated from the main branch (6) by a transverse par- 

 tition. C. an open oogonium expelling a drop of mucilage, si. D, spermatozoids. £", 

 spermatozoids collected at the mouth of the oogonium. F, the antheridium, a, col- 

 lapsed after the escape of the ppermatozoids ; osp, the oospore. X about 100, except 

 Dj which ismuch more. — C, X>, after Pringsheim, the others after Sachs. 



(a) The formation of zoospores begins in tlie niglit, tliey escape in 

 the morninfT, and the night following they germinate. 



(6) The formation of sexual organs begins in the evening, and is 

 completed the next morning ; fertilization takes place during the day 

 {from 10 A.M. to 4 p.m.). 



(c) Good specimens of VaucAeria may be found clothing the boggy 

 ground about many springs. The bright green mats may be trans- 

 ferred to the aquarium for the study of zoospores ; but for the sexual 

 organs the dingy and dirty looking specimens must be collected. 



