248 



BOTANY. 



consists of a rounded oosphere situated within a cavity — the 

 oogonium ; it is deTeloped from one of the cells (sometimes 



two) of the filament 

 by a condensing 

 and rounding off 

 of the protoplas- 

 mic contents; when 

 the oosphere is ful- 

 ly formed, an open- 

 ing is formed in 

 the oogonium-wall 

 for the ingress of 

 the spermatozoids 

 {A and B, Fig. 

 167). One or more 

 spermatozoids are 

 produced in each of 

 certain small cells 

 which are formed 

 from the large ones 

 by a process of 

 simple fission ; in 

 shape they resem- 

 ble the zoospores 

 mentioned above — 

 that is, they are 

 oval and provided 

 with a crown of 

 vibratile cilia on 

 their smaller ex- 

 tremity {D, z, z, 

 Pig. 167). Upon 

 escaping into the 

 water, which is ren- 

 dered possible by 

 a splitting of the 

 wall of the mother- 

 cell, they swim about vigorously, and eventually make their 

 way through the opening in the oogonium, and then bury 



Fig. 167. — A, middle part of a eexual filament of (Edo- 

 gonium ciliatum {Androg^nia of Wood), with male cells 

 above at m; og, oogonia (fertilized) ; m, dwarf male 

 plants attached to the side of the oogonia, the sperma- 

 tozoids already discharged. X 250. B, oogonium, og, 

 at the moment of fertilization ,* o. the oosphere ; a, the 

 Bpermatozoid forcing its way into the oosphere ; m, the 

 dwarf male plant. 6', ripe oospore. D, (Edogonium 

 gemelUparwm (Pringe/ieimm of Wood), part of the male 

 filament, with spermatozoids, s, issuing from the cells. 

 Ey part of a branch of Bulbockcete intermedia, with oogo- 

 nia, the uppermost containing an oospore, the middle 

 one with an oospore escaping, the lower empty. F, four 

 zoospores resulting from an oospore of BvlbocluEte. O, 

 zoospore come to rest and germinating.— After Prings- 

 beim. 



