CHAPTER VI. THE THALLOPHVTA. 303 



globular depressions in the surface. The walls of the concep- 



tacles are lined with hairs, some of which protrude from the nar- 



j^ row opening. Among these 



Mg^ |1M /eS^ j^^k hairs, on the interior of 



'^^^^^^ some of the conceptacles, 



\ \V ^ iSm are borne anth eridia, and in 



species, for example, Fucus 



IMM wSfllfl&iliPl^ i platycarpus, both are borne 



~mM lW(m^ * n tne same conceptacie. A 



' ■ " female conceptacie is shown 



^|Lw% WSk mm The antheridia are branch- 



■ ili / // m ° filaments, some of the 



I v Vm K II cells of which, when mature, 



emit numerous bi- ciliated 



1 * // antherozoids. These find 



/'' ' J / "\ I their way to the oospheres, 



which, in the meantime, have 



//" escaped from the oogonia 



and fertilize them. Fig. 503 



■ shows one of the branching 



Fig. 501. — Portion of thallus of Fucus ves- -. , . , 



iculosus about natural size ; a, one of the blad- filaments bearing anttier- 

 ders ; />, fruiting organs. .,. 



The oogonium begins as a minute papilla-like protuberance 

 on the wall of the conceptacie, and is at first a single cell. This 

 divides transversely into two cells, the lower one constituting the 

 stalk, and the other becoming the oogonium proper. This be- 

 comes relatively large in size and spheroidal in form, and, in this 

 species, the protoplasmic contents break up into eight nearly 

 equal portions, forming as many oospheres. In most other 

 members of the order, either no division takes place, and but a 

 single oosphere is formed within the oogonium, or else fewer are 

 formed than in Fucus. 



When the oospheres are fully formed, the wall of the oogo- 

 nium ruptures and they are discharged into the water, and there 

 the antherozoids swarm about them and fertilize them. See Fig. 

 504. After this process is completed the oospore acquires a cell 

 wall, and soon begins to germinate. 



