DEVELOPMENT OF THE PERITHECIUM. 13 



plasm becomes a dense, shrunken, highly stainable mass, as will be 

 described in more detail a little later. 



It is to be noted that in Phyllactinia there is no lack of granular 

 material in the disintegrating cytoplasm of the antheridium to represent 

 a degenerating nucleus for one who, like Dangeard, has failed to find 

 the real process of fertilization. Apparently the fusion of the pro- 

 nuclei occurs in about the center of the oogonium. The fusion nucleus 

 is slightly larger than either of the pronuclei (figs. 10, 1 1) and may show 

 an increased density of its chromatin for a time (fig. 10). Details of 

 the fusion-process and the union of the different parts of the pronuclei 

 in the fusion-nucleus, so far as I have been able to observe them, are 

 presented later in connection with my studies of the fusion of the nuclei 

 in the ascus. After fusion the nucleus lies in the middle region of the 

 oogonial cell (figs. 10-12). 



The conjugation-pore leading from the antheridium into the egg 

 cell is closed at once after the passage of the male nucleus (fig. 10) and 

 the antheridial cell now undergoes some very interesting and character- 

 istic degenerative changes which make it a most conspicuous object all 

 through the earlier development of the ascocarp, and which in them- 

 selves are conclusive evidence that it is a differentiated gamete-cell 

 differing entirely in its nature from the cells of the perithecial envelopes. 

 These changes consist in a swelling and change in composition of the 

 antheridial wall and the shrinkage of the protoplast. Up to the time 

 when the conjugation-pore is closed the antheridial cell-wall has been 

 of the same thickness as that of its stalk cell and of the oogonium, and 

 has showed ho tendency to stain differently than the walls of these cells. 

 With the triple stain the walls in these stages tend to stain pale blue. 

 Very soon after the fusion pore is closed, however, the antheridial 

 cell-wall begins to increase very markedly in thickness by swelling and 

 undergoing what seems probably to be a mucilaginous degeneration 

 (fig. u). This swelling is all toward the interior of the cell. With 

 the swelling of the wall the protoplast apparently shrinks together, still 

 keeping, however, the general outlines of the cell. The surface layer 

 of the cell- wall remains dense and sharply marked, and the antheridial 

 cell as a whole maintains its contour quite unchanged or with a very 

 slight sinking in of the walls, indicating diminished turgidity. 



This swelling of the wall continues until its thickness is equal to 

 one-fourth or more of the transverse diameter of the entire antheridial 

 cell (figs. 12-20, 23, 24). The swelling is least in most cases on the 

 cross-wall cutting off the antheridium from its stalk cell and greatest 

 on its outer wall opposite the region in which it is pressed against the 



