British Fwio-i. 



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contaiuing numerous drops of oil^ tliese swellings or 

 oogonia are cut off from continuity with the cavity of 

 the hypha by a septum if terminal, or by a septa on 

 each side o£ the oogonium when intercalary. At this 

 stage of development the protoplasm of the oogonium 

 becomes differentiated, the denser portion along with 

 the oil drops forms a sphere in the centre — the oospliere 

 — which is furnished with a delicate membrane, and 

 is surrounded by a layer of hyaline protoplasm, 

 known as periplasm. Contemporaneous with the 

 development of the oosphere the antheridium is 

 formed, which is the swollen apex of a lateral branch, 

 springing from the hypha bearing the oogonium at a 

 short distance below the latter. The antheridium 

 when fully developed is more or less elliptical or 

 obovate, much smaller than the oogonium, richly filled 

 with granular protoplasm, and cut off from the cavity 

 of its supporting hypha by a septum. When the 

 oosphere is formed the antheridium comes in contact 

 with the oogonium, and at the point of contact sends 

 a thin tube throuo^h the wall of the ooo^onium, which 

 continues to grow until it reaches the surface of the 

 oosphere. During the growth of the fertilization-tiihe 

 the protoplasm of the antheridium undergoes differen- 

 tiation into a central dense mass, the gonoplasm, and 

 a thin peripheral portion. The gonoplasm passes 

 along the fertilizatioii-tuhe, through an opening 

 formed at its apex, and mingles with the protoplasm 

 of the oosphere, which at once secretes a thick cellulose 

 wall, and is known as the oospore. Modification of 

 the above method takes place in different species and 

 genera, for instance, sometimes several oospheres are 



