Damping Off. 30^ 



the oogonium, being 14/^-18// in dimeter. This central sphere of 

 coarsely granular protoplasm is termed the oosphere, or egg cell,, 

 and is really an unfertilized e^g, the receptive cell of the oogonium. 

 Between this egg cell and the wall of the oogonium is a space tilled 

 with a nearly clear, but finely granular and homogeneous fluid 

 called the periplasm. At this stage there is no wall surrounding- 

 the egg cell and it is ready to be fertilized. 



Antheridia. — The sole purpose of the antheridia is to supply the 

 fertilizing element for the egg cell, and the antheridium is some- 

 times termed the supplying gamete, while the oogonium is termed 

 the receptive gamete. The antheridia are of two kinds, stalk 

 antheridia and branch antheridia. A stalk antheridium is formed 

 from a section of the oogoniophore by the formation of a partition 

 wall in the hypha cutting off an elongated cell one end of which is- 

 thus in contact with the wall of the oogonium, and its contents are- 

 only separated from those of the oogonium by the wall of the latter. 

 This is the simplest of the two forms of the antheridia. 



A branch antheridium is developed as a lateral branch of the 

 oogoniophore, arising, usually quite near the oogonium, but some- 

 times more or less remote from it, rarely on a separate hypha. 

 The branch grows towards the oogonium and its rounded end 

 comes in contact with the oogonium wall and becomes flxed at the- 

 point of contact. A septum is now formed in the branch cutting 

 off an elongated cell varying from 15//-40//. This cell, one end of 

 which is in contact with the oogonium wall, is the antheridium, and 

 the proximal portion of the branch is the antheridiophore. More 

 than one antheridium may be formed in connection with a single 

 oogonium, frequently two and sometimes three. Both may be 

 branch antheridia, or one may be a branch antheridium and the 

 other a stalk antheridium, and other combinations may take place 

 where more than two antheridia are present. There does not seem 

 to be any rule in the number of antheridia which take part in the 

 fertilization of the egg cell. "Where several are in contact one or 

 more may take part in the act of fertilization. 



When the antheridial cell is formed its farther development is^ 

 the same whether it be a branch an heridium or a stalk antheridium. 

 The cell which is cylindrical or nearly so in form begins to swell 

 and this continues until it is two to three times the original diameter, 

 the greatest diameter being near the end which is in contact with 

 the wall of the oogonium. At the same time it also becomes quite 



