THE TIIALLOPHYTA 



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ing filaments among which arc placed the antheridia and oogonia 

 (Fig. 159). The antheridia arc small cells arising on branches of 

 the filaments and producing swarms of biciliate sperms. The 

 oogonia are larger cells, the contents of each dividing into eight 



Fig. 159. — Fucus. A, female conceptacle, with oogonia and sterile filaments. 

 B, single oogonium at maturity, containing eight eggs. C, group of antheridia 

 from a male conceptacle. D, sperms. E, egg after discharge into the water, 

 surrounded by sperms. F, young plant arising from an oospore. (5, C, D, E 

 and F after Thurel). 



eggs. In some species both sex organs are produced in the same 

 conceptacle, in others they occur in different conceptacles on the 

 same plant, and in still others the whole plant is entirely male or 

 entirely female. Both eggs and sperms are discharged from the 

 mouth of the conceptacle and fertilization takes place in the open 



