258 



PART IV. CLASSIFICATION. 



\ 



matozoids resemble the zoospores, but are smaller and are yellow instead 

 of green; they are set free, and finding their way to the oogonia, one 

 enters an oogonium and fertilises the oosphere, penetrating into it at the 

 receptive spot (Fig. 147). 



In some species, termed gynandrosporous, the filaments produce no 

 antheridia, but only oogonia. Some of the cells of such a filament under- 

 go transverse division to form short cells which somewhat resemble 



antheridia. The con- 

 tents of each of these 

 cells are set free as a 

 single zoospore, termed 

 an androspore, interme- 

 diate in size and colour 

 between the ordinary 

 zoospores and the sper- 

 matozoids, and resem- 

 bling them in form. 

 The androspore comes 

 to rest, attaching itself 

 to the wall of an oogon- 

 ium (Fig. 147), and ger- 

 minates, forming a 

 small filament, known 

 as a dwarf-male, which 

 consists of a root-cell 

 and two or three cells 

 above it; each of these 

 upper cells is an aiither- 

 idium, and its contents 

 are set free as a single 

 spermatozoid. 



On germination, the 

 contents of the oospore 

 are set free as four 

 zoospores, each of which 

 develops into an (Edo- 

 gonium- plant. Fresh- 

 water plants : genera 

 CEdogonium, Bulbo- 

 chsete. 



Order 5. Coleochae- 

 taceae. Body filamen- 

 tous, branched, forming 

 hemispherical or disc- 

 shaped cushions on sub- 

 merged stones or parts 

 of water - plants ; the 

 mode of growth is es- 



FIG. 147. A (Eclogonium ciliatum (x 250). A Middle 

 part of a sexual filament with three oogonia (og) fertilised 

 by the dwarf-male plants (m), developed from androspores 

 formed in the cell TO at the upper part of the filament. 

 B Oogonium at the moment of fertilisation : o the 

 oosphere ; og the oogoninm ; z the spermatozoid in the 

 act of forcing its way in ; m dwarf-male plant. C Ripe 

 oospore. D Piece of the male filament of (Ed. gemelli- 

 porum, z spermatozoids. E Branch of a Bulbochcete, with 

 one oogoninm still containiog an oospore, another in the 

 net of allowing it to escape; in the lower part an empty 

 oojronium. F The four zoosporea formed from an oospore. 

 G Zoospore come to rest. (After Pringsheim.) 



