CHARACE.E 417 



with difficulty in the whole oogonium, owing to the 

 density of its contents, may be satisfactorily seen. 



The development of the oogonium should be studied in young 

 buds, teased out with needles (or cut in longitudinal section), and 

 treated with potash : in these it will be seen how the five cells, 

 which are to form the coat and crown, gradually grow over the 

 central cell : that they are straight at first and become subsequently 

 coiled, and that the terminal part of each is cut off to form the 

 crown. 



The essential characters of the oogonium of Nitella are similar, 

 but the crown consists of two series of five cells, one above the 

 other, and several small cells may be found cut off at the base of 

 the ovum. The position of the oogonia is also different, two being 

 usually disposed, right and left, below the terminal antheridium. 



VIII. Examine mature oogonia and note the dark 

 colour, and the thickened, lignified wall of the spiral 

 cells, while the oospore itself is surrounded by a thick, 

 colourless wall. Burst one by pressure upon the cover- 

 slip, and it will be seen that the contents consist 

 largely of starch and oil. 



IX. The results of germination may be readily 

 observed in Chara or Nitella, if specimens with mature 

 oospores be kept in water in a bell-glass through the 

 winter : in the spring the oogonia which had settled to 

 the bottom may be found in various stages of germina- 

 tion. Some may be seen still closed at the apex : in 

 others the spiral cells may have ruptured at the apex 

 and two or more transparent filaments project : one of 

 these develops more strongly as the proembryo, it 

 divides by transverse walls, and assumes a green colour : 

 the other remains colourless and develops into rhizoids. 

 In one of the filaments which is far advanced observe a 

 narrow, disc-shaped cell, two or three cells short of the 



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