112 



contains a considerable amount of oil, numerous chloroplasts, and 

 after the appearance of its basal wall, only one nucleus. That 

 portion of the protoplasm towards the apex or beak becomes clear 

 and free from chloroplasts, and is termed the receptive spot. The 

 cell-contents now become rounded off, forming the ovum (or 



Fig. 43. A and B, Vaucheria sessilis (Vauch.) D. C. ; A, from Esher West-end 

 Common, Surrey; B, from Mitcham Common, Surrey. C and D, V. hamata 

 (Vauch.) Lyngb., from Calverley, W. Yorks. E, oogonium and oospore of 

 V. sericea Lyngb., from Beverley, E. Yorkshire. (A D, x200; E, x320.) 

 a, antheridium ; an, antherozoid; oo, oogonium. 



oosphere) and soon afterwards the wall of the oogonium opens at 

 the extremity of the beak, a small quantity of mucilaginous pro- 

 toplasm being exuded. 



The antheridia develop simultaneously with the oogonia and 

 generally in close proximity to them. (Fig. 42 E.) Each anthe- 

 ridium arises as a short cylindrical branch which usually becomes 

 much curved on approaching maturity. (Fig. 43 A and B.) The 

 terminal portion of this curved branch is cut off by a septum and 

 becomes the actual antheridium. In some species, such as in the 

 submarine Vaucheria synandra, a number of antheridia occur on a 

 structure known as an " androphore." The protoplasm of each 

 antheridium contains numerous chloroplasts and nuclei. The 

 nuclei collect in the central portion of the antheridium and it is 



