ASCOMYCETES AND RHODOPHYCEv. 



42, D). During this process, or sometimes later, as stated in a pre- 

 ceding paragraph, the nuclei of the trichogyne disintegrate. When 

 this has taken place the antheridial nuclei begin to migrate through the 

 pore into the trichogyne, whose protoplasmic contents become still 

 further disorganized. This migration of nuclei continues until the 

 tube is quite densely filled and sometimes slightly swollen (Fig. 42, E). 

 In the meantime conspicuous changes have been taking place in the 

 oogonium. The nuclei, which are evenly distributed throughout the 

 interior of this organ, begin to migrate toward the center, where they 



*^ Y- v*^*-i -;w . i?a 



^i,? ; *:^f 



E 



FIG. 42. Copulation of sexual organs of Pyronema. (After Harper.) 



D, the trichogyne has copulated with antheridium, nuclei in trichogyne disintegrated ; hypothecial 

 hyphae springing from stalk cells. 



E, trichogyne filled with nuclei from antheridium ; antheridium curved around trichogyne so that the 



latter appears in section to cut through it ; trichogyne still separated from oogonium by transverse 

 wall. 



become collected into a dense, hollow sphere, equal in diameter to 

 about half that of the oogonium, or they may aggregate into an irreg- 

 ular, crescent-shaped mass in either the upper or lower half of the 

 oogonium (Fig. 42, E). Less frequently several masses of nuclei are 

 formed instead of one. 



The cytoplasm of the oogonium, which was charged with densely 

 staining substances, becomes tenuous and loosely spongy in texture. 

 After the oogonial nuclei have aggregated in the center of the egg-cell, 

 the basal wall of the trichogyne breaks down and the antheridial nuclei 



