THE ALG.E 



179 



unused protoplasm, some of which, however, remains 

 behind. 



In the mean time the development of the oogonium 

 has been going on. Arising, like the antheridium, as a 



O 



sp. 



===^^^^#mmmmm^. 



?:a^V^?-^f ? '^^G^5?W' : ^VQi' ; ^:?; 



a 



FIG. 76. Fertilisation of Vaucheria terrestris. A, part of 

 filament, bearing two reproductive branches ; a, antheridium; 

 o, oogonium. On the right an early stage is shown. On 

 the left the antheridium is already empty, and the oogonium 

 fertilised. B, right hand group of Fig. A later on, showing 

 fertilisation. The minute spermatozoids (sp) are caught in 

 the drop of mucilage expelled from the oogonium. Anther- 

 idium of same branch not yet open. C, some time after 

 fertilisation. The antheridium and filament are empty, and 

 the ob'spore is ripening. D, ripe oospore, containing oil- 

 drops. Magnified 110. (R. S.) 



lateral outgrowth (or as in the species figured, at the 

 end of the pedicel), it soon assumes a globular form. 

 The protoplasm of the oogonium contains a large 

 quantity of oil, as well as chloroplasts, and at first a 



