234 



GENERAL BOTANY 



The female gametangium (Fig. 123, a) is a greatly enlarged 

 cell of the filament, in which the protoplast differentiates as a 

 large female gamete. The male gametangia are developed from 

 small cells of a filament, in which each protoplast usually forms 

 two male gametes. Fertilization results in a resting zygote, 

 which, after a period of rest, germinates by the division of its 

 protoplast to form four free-swimming zoospores (Fig. 123, , d). 



Ooyonhim 



Female 

 fjamete 



- Zygote -/- f 



...Cell 

 v wall 

 "Cytoplasm 

 iiclcus 

 Zoospores 



Antheridia 



FIG. 123. Sexual reproduction in (Edogonium 



a, gametes and fertilization; 6, zygote with heavy cell wall in resting condition; 

 c, cell division of the protoplast to form four zoospores; d, zoospores formed from 

 the divisions of the protoplast in c ; e, growth of the zoospores into young plants after 

 becoming attached to a rock in the water, a, after Coulter ; b-d, after Him ; 



e, after Juranyi 



These zoospores become free-swimming by the disorganization 

 of the old zygote cell wall, come to rest on a support, and begin 

 to elongate into a new filament. This new plantlet (e) is at 

 first attached but later becomes a free-floating filament like the 

 parent organism. 



In asexual reproduction zoospores are formed much as in 

 Vaucheria except that they arise from protoplasts of cells 

 within the filament (Fig. 124). Each zoospore becomes free 

 from the mother plant by the rupture of the mother-cell wall 

 and swims freely in the water for a short period. It then loses 

 its cilia, becomes attached to a support, and forms a new 

 filament, exactly as in the case of zoospores developed within 

 the zygote. 



