DEVELOPMENT OF PLANTS 



209 



cell wall which later ruptures and sets them free (Fig. 124, B). 

 The female gametes are without cilia and as they float away in 

 the water they appear to attract the male gametes which swarm 

 about them and finally fertilization is effected by one of the male 

 gametes working down to the nucleus of the female and fusing 

 with it (Fig. 124, C). In an allied form not only is an attractive 

 substance formed in the female gamete, but probably a repellent 



Fig. 124. Female gametangia: A, greatly enlarged view of one of the 

 oogonia shown in Fig. 122, C. The oogonium is dividing and forming the 

 female gametes; p, paraphyses. B,- the female gametes discharged but still 

 retained in the inner wall of the oogonium. C, greatly enlarged view of a 

 gamete which is surrounded by male gametes, some of which are seen as 

 dark bodies penetrating the cytoplasm of the female gamete. D, early stage 

 in the germination of the gametospore. See later stage, Fig. 121, C. — ^After 

 Thuret. 



one after fertilization is effected, for Farmer observed that the 

 male cells swarm about the female cells for a time and then sud- 

 denly swim away "like a flock of frightened birds." As soon as 

 fertilization has been effected, the gametospores become invested 

 with a cell wall and attached to the rocks. Cell division now 

 proceeds rapidly and soon establishes the characteristic thallus 

 of the plant (Figs. 124, D; 121, C). Fucus is a very prolific plant 

 14 



