220 



A TEXTBOOK OF THEORETICAL BOTANY 



behind it. In shape these antherozoids resemble the zoospores, but they are 

 smaller and their amoeboid movement is more pronounced. 



The Oogonium 



After the antheridium has been cut off by a septum, the proximal portion 

 of the hypha below the septum becomes distended and forms a lateral pro- 

 jection, which finally enlarges into a clavate body which is also cut off by a 

 cross wall. The oogonium gradually becomes more rounded in shape. The 

 contents then move away from the wall, forming a central spherical oosphere. 



Oosphere 



Antheridium 



A / 



Oosptiere 



Oogonium 



B 



Fig. 2IO. — MonoblepJiaris polytiiorpho. Stages in the development of the oospore. 

 A, Extrusion of the oosphere. B, Liberation of antherozoids. C, Mature oospore. 



In certain species the oogonium is formed terminally at the end of the hypha, 

 and after it has been separated by a septum the portion of the hypha below 

 forms a lateral projection which grows out as an hypogynous antheridium. 

 In one species, Monoblepharis macrandia, the oogonium and antheridium 

 occupy terminal positions on separate hyphal branches. In this case, as 

 growth continues, additional antheridia or oogonia may develop below the 

 terminal ones, which therefore appear to be produced in chains. 



When the oosphere is mature the oogonium opens at the top to allow 

 entry for the antherozoid, and mucus is secreted through the opening by 

 means of which the antherozoid becomes attached and its union with the 

 oosphere follows immediately (Fig. 210). 



The Oospore 



The genus Moiwblepharis is sometimes divided into two sub-genera 

 which are distinguished by whether the oospore develops within the oogonium 

 (Fig. 211) or whether it leaves the oogonium immediately after fertilization 

 and completes its maturation outside the mouth of the oogonium. In 



