I50 



MORPHOLOGY, 



forms two spcrmatozoids {sometimes only one) which arc of the same form as 

 the zcKjgonidia but smaller, and yellnwish insteatl of screen. In some species 



a motile body intermedi- 

 ate in size and color be- 

 tween the spcrmatozoids 

 and zooj^^onidia is first 

 formed, which after 

 swimming- around comes 

 to rest on the oogonium, 

 or near it, and develops 

 what is called a " dwarf 

 male pl?nt " from which 

 the reai spermatozoid is 

 '/ produced, 

 p ^- ^T*,!"''', f ^ 3,18. oog-onia. - The 



i^nrtiriD or tnreafi or rjedo- . 



gonium showing upper half Oogonia are formed di- 



Fig. 147. 

 Portion of thread 

 o f oedogonium 



showing antheridia 



of egg open, and a sperina- 



recti\' fr(.)m one of the 



toxoid ready to enter. (After 



Klebahn). vegetative cells. In most 



species this cell first enlarges in diameter, so that it is easily detected. The 

 protoplasm inside is the egg cell. The oogonium wail opens, a bit of the 

 protoplasm is emitted, and the tpcrmatozoid then enters and fertilizes it 

 (fig 148). Now a hard brown wall is formed around it, and, just as in spirogyra 



Fig. 149- Fig. 150. Fig. 151. 



Male nucleus just entering Male nucleus fusing with The two nuclei fused, and 

 egg at left side. female nucleus. fertilization conijilete. 



Figs. 149-1 51.— Fertilization in cedogonium. (After Klebahn). 



.'ind vaucheria, it passes through a resting period. Atthe time of germinatiot 

 it does not produce the thread-like plant again directly, but first forms fan 

 zoospores exactly like the zoogunidia {fig. 152). These zoospores ther 

 germinate and form the plant. 



319. (Edogonium compared with spirogyra. — Now if we compare cedo- 

 gonium with S[iirogvra, as we did in llie < a^e of vauehoria. we find here also 

 Uial there is an advance ujuhi the .siin|ilc Condition which exi^t.s 111 spin>- 

 g\ra. * iiowtli and di\isi(in o| iIk' lliread is limiled to eeruiin poiiions. Ihe 

 sexiKil organs aie dilTerenliaK d. Tliev usually <lilTer in form and si/e from 

 tlie vegetative cells, though liie u<.igi>niuni is simjdy a changed vegetative 



