JEHANGIR FARDUNJI t)ASTUR. 20l 



rather old hypha somewhere in its middle. Thus according to 

 its development the antheridium is terminal or intercalar. The 

 swollen portion of the hypha is soon cut off by one or two septa 

 according as it is terminal or intercalar. The walls of the swell- 

 ing remain thin or become slightly thicker than those of its stalk. 

 There is no trace of the oogonium till the antheridium is completely 

 developed, or almost so. The oogonium and the antheridium are 

 on the same stalk or on different stalks. When they are on 

 the same stalk the oogonial hypha arises from the base of the an- 

 theridium as an ingrowth (Plate VI, Figs. 3 and 4). When the 

 oogonial origin is developed on a separate hypha, it grows towards 

 the antheridial swelling and makes its way into the interior of 

 the latter when it comes in contact with it. In some cases the 

 oogonial hypha swells before penetrating the antheridium (Plate VI ? 

 Fig. 14), in rare cases it has been found to indent into the wall of the 

 antheridium before boring its way through it (Plate VI, Fig. 2). 

 Once within the antheridium the hypha continues its growth until 

 the apex is reached. At this stage the swollen apical wall of the 

 oogonial hypha is thinner than its side walls (Plate VI, Figs. 4 to 

 7), and its apex is also more highly refractive than the rest of the 

 hypha. The swollen head of the oogonial hypha now dissolves the 

 antheridial wall in contact with it and grows out of it. Imme- 

 diately it emerges it, as a rule, swells out into a sphere or almost a 

 sphere containing oil drops, the oogonium proper. When the 

 oogonium is mature its protoplasm gets differentiated into the 

 oosphere, surrounded by a very thin hyaline wall. Later on 

 changes take place in the oosphere, the thin wall begins to get 

 thickened and contracts a little from the oogonial wall. There is a 

 simultaneous change in the oogonial wall as well : it also gets thicken- 

 ed and turns yellow. These changes mark the conversion of the 

 oosphere into the oospore, after fertilisation, but the exact moment of 

 fertilisation cannot be ascertained ; at no stage in the development 

 of the antheridium and oogonium has ever been found any special 

 process through which the fertilisation might be effected, probably 

 on account of the way in which the antheridium envelops the oogoni- 



