REPRODUCTION 



433 



In the group of Fungi similar differentiation of gametes 

 occurs, but motile antherozoids are very rare, confined 

 indeed to the genus MonoUepharis. In many cases they 

 are undifferentiated masses of protoplasm which do 

 not escape from their antheridia, but are conducted 

 directly from it into the female organ, where the process 

 of fusion takes place. In Pyihium the oogonium is a 

 swelling at the end of a hypha, which is cut off from the 

 rest by a transverse wall. Its contents divide up into an 

 oosphere and a certain amount of protoplasm, which sur- 

 rounds the sexual cell. The antheridium is another hyphal 

 branch, which becomes closely pressed to the oogonium. 

 A tube is put out by the antheridium, which perforates the 

 wall of the oogonium, and the male cell, which is formed 

 in the same way as the female one, 

 passes over into the female organ and 

 fuses with the oosphere. 



In some other Fungi a similar 

 arrangement of the organs is brought 

 about, but the male cell does not pass 

 over into the oogonium. 



A curious variation is seen in the 

 red seaweeds, the Rhodophycece. The 

 female organ, known as a procarpium, 

 does not produce any differentiated 

 oosphere, but the contents of the 

 male cell pass by means of an elon- 

 gated structure, called a trichogyne 

 (fig. 172), into its interior and appa- 

 rently fuse with the whole of its 

 proto plasm. The male cell in these 

 plants is not naked as in other cases, 

 but has a cell- wall. A somewhat simi- 

 lar condition is met with among the Ascomycetes, though 

 whether fusion of the contents of the cells takes place is 

 disputed. 



Except in the Angiosperms the gametangia of the plants 



28 



172.-PKOCAKWUM OF 



A RED SEAWEED. 



tr, trichogyne. 



