BROWN ALGAE 



38: 



by the forward cilium. Such fixed females become centres of attrac- 

 tion for the still motile males, which collect round them in number, 

 and come into contact with the female by their forward cilium 

 (Fig. 321, i). Presently one of them draws up to the female and 

 begins to fuse with it (2) ; all the rest at once move away. Gradually 

 the fusion is completed (3-5), the resulting zygote rounds off and 





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Fig. 319. 

 .4, Mature male conceptacle of Fucus serratus, filled with br.n 

 hairs. (After Thuret.) B, .Mature femcle conceptacle of 

 containing unbranched hairs, and oogonia. (After Thuret.) 1; 

 drawings show the structure of the mature thaUus (p. 379)- 



forms a cell-wall, and may presently germinate into a m-w pi.mt. 

 In E. siliculosus both types of sporangia and of gametes arc alike in 

 form. But in E. secundus the sporangia {gametangia) are not alike ; 

 and they produce gametes of different sizes (Fig. 322, \.). The smaller- 

 celled gametangia [anthevidia) produce smaller gametes that arc male 

 {spermatozoids, ii.) ; the larger-celled (oogonia) produce large: 

 that are female [ova, iii.). But still they are of the same for::, 

 zoospores of the whole group. After their escape the ova soon lose 

 their motility, and their fertilisation by the smaller spermatozoids 



