DEVELOPMENT OF PLANTS 



197 



female gametes are produced in larger sacs or oogonia, which 

 are each supported on a single cell and associated with hair-like 

 chains of cells, paraphyses (Fig. 124, A). Usually eight gametes 

 are developed in each oogonium. The gametes when first dis- 

 charged from the antheridia and oogonia are enclosed in a delicate 

 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 



Fig. 123. One of the branching filaments from Fig. 122, B, greatly en- 

 larged. Some of the antheridia, an, have discharged the male gametes, which 

 are still retained in the inner wall of the antheridium, as at b. At a this 

 wall is ruptured, freeing the gametes. 



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 

 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 

 and the reproduction process can be observed at almost any time. 

 After the plants have been exposed for several hours by the low 

 tide the male and female gametes will often be found forming 

 orange yellow and olive green drops at the mouth of the cavities. 

 In this condition the entire process of fecundation and early stages 



