BUTLER AND KULKARNI. 249 



a neighbouring, but distinct, hypha. This is the oogonial origin. 

 As the apex reaches the wall of the antheridiuni, it indents it and 

 then penetrates into the antheridial cavity. Usually it pursues a 

 straight course to the opposite wall, which it again pierces to emerge 

 on the further side. Sometimes it bends within the antheridiuni 

 so that the point of exit is not opposite that of entry. The 

 free apex now at once swells up into the oogonial cell, the swelling 

 sometimes extending back to a part of the stalk within the anthe- 

 ridiuni which is either depressed into a cup-shaped hollow in which 

 the oogonium sits or broadened out where the stalk emerges (PI. 

 IV, Figs. 4 to 12). The oogonium remains closely applied to the 

 antheridiuni at its basal part and is apparently fused with it over 

 a considerable extent. When the oogonial cell has reached its 

 full size it is cut off by a septum, which is generally formed in the 

 part of the stalk within the antheridiuni (PI. IV, Figs. 6 and 13). 

 The contents now contract away from the oogonial wall to form 

 the oosphere, which ultimately develops a thick wall and lies loose 

 in the oogonium, which it does not completely fill. At what stage 

 fertilisation occurs could not be determined, no fertilisation tube 

 having been detected. 



So far as could be determined the oogonium arises always 

 from a different hypha from that which bears the antheridiuni. 

 Sometimes, however, the stalks of both organs swell up and a 

 tangled mass results which prevents their origin being ascertained 

 (PL IV, Fig. 14). In most cases where the oogonial stalk could be 

 followed back it arose as a lateral branch from a larger hypha. In 

 one case (PI. IV, Fig. 11) the oogonial stalk became swollen and 

 gave off two short branches which pierced two antheridia and 

 bore two oogonia. 



After the oogonium forms, the wall of the antheridiuni thickens 

 somewhat, without becoming coloured, and remains clearly visible 

 for a long time. The oogonial wall also thickens, sometimes con- 

 siderably, and takes a yellow colour. The oogonial stalk below 

 the antheridiuni is less persistent and in many cases disappears 

 so as to give the impression that the oogonium arises as an ingrowth 



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