VAUCHERIA. 72 <5 



set free is an asexually produced swarm-spore, which is provided with a velvet-like pile 

 of minute short cilia over its whole surface ; it swims about with a rotatory motion for 

 a short time only after its exit in the early morning, and at length becomes fixed some- 

 where and then germinates {D and ^, p. io8). In the figure referred to is repre- 

 sented the sexual apparatus also of this Vaucheria, at F in og and h, and the Fig. 

 415 annexed gives a more exact insight into the processes of fertilisation. It is only 

 after prolonged cultivation, when numerous generations of plants have been produced 

 by means of asexual swarm-spores, that sexual organs also appear. These, in 

 accordance with the simple structure of the Vaucheria, are formed by the develop- 

 ment of protuberances from the utricular shoot, as in Fig. 41^ A utog and h. The 



f -B 





FIG. 4TS —Vntickeria sessiiis. A, B development of the antheridium a on the branch h, and of the oogonium og. 

 C an oogonium which has opened and sent forth a drop of slimy substance. D antherozotds. £ antherozoids 

 collecting at the [mouth of an open oogonium . f, cz En emptied antheridium ; osfi oospore in the oogonium. {A, B, E,F 

 from Nature; C, D after Pringsheim.) 



Stouter shorter protuberance, the future oogonium, fills itself with protoplasm contain- 

 ing abundance of chlorophyll, and grows up into a body which has approximately 

 the shape of an oblique lemon {og in B) joined to the tubular vegetative branch by a 

 very short stalk-like portion. At this place the mass of protoplasm which has 

 collected within the oogonium becomes separated off from the vegetative part of the 

 plant by a transverse wall. At length the apical papilla of the oogonium opens, 

 the protoplasmic body contracts a Httle, rounds itself off, and expels a drop of slime 

 through the open neck — a process which occurs in many other cases of fertilisation, 

 and is perhaps quite general — (C at si). While the oogonium thus prepares for 

 fertilisation, there is developed on the tubular process h, which eventually becomes 

 curved like a beak, the antheridium a (in B). In this also protoplasm collects, and 

 becomes divided off by a transverse wall from the stalk-like portion of the beak, 

 and then breaks up into a very large number of extremely minute corpuscles, 



