1905.] Development of the Ascocctrp q/*Humaria granulata. 357 



granules apparently fuse together, for when the ascogonium has reached its 

 full size this wall shows two large and deeply-staining masses placed 

 opposite one another on either side of the wall (fig. 13). The masses 

 sometimes show a central deeply-staining portion, and an outer, irregular, 

 less dense portion (fig. 13). When the ascogonium and stalk cells become 

 emptied these masses disappear. Besides the special accumulation on the 

 walls a number of large granules are usually to be found scattered in the 

 cytoplasm of the ascogonium and stalk cells (fig. 9). 



When the ascogonium has become covered in with several layers of vege- 

 tative hyplne the ascogenous hyphae appear as narrow, thin-walled outgrowths 

 from the thick-walled ascogonium, and make their way through the close 

 mass of investing hypha? (figs. 10, 11). Into the ascogenous hyphae there 

 pass nuclei and cytoplasm from the ascogonium, which becomes more and 

 more vacuolate in appearance and is finally almost completely depleted. 



It is clear that the ascogonium which produces the ascogenous hyphas has 

 undergone no process of fertilization by male nuclei, so the development at 

 first sight appeared to be a truly parthenogenetic one. When, however, such 

 a case as the development of the accidium of Phragmidium violaceum 

 (Blackmail, 5) was considered — where, in the absence of the male cell, there 

 is a peculiar process of fertilization by the union of a vegetative cell with the 

 female cell— it seemed conceivable that a reduced process of a somewhat similar 

 nature might be found in IT. granulata also. If this were so, two possi- 

 bilities presented themselves ; either the ascogonium might be fertilized by the 

 entrance of the contents of the uppermost stalk cell or of some other vege- 

 tative cell, or a fusion in pairs of the nuclei of the ascogonium might take 

 place. As no evidence of the first possibility could be obtained, the ascogonial 

 contents were very closely examined at various stages of development, with 

 the result that the second hypothesis was found to be correct, and the female 

 nuclei were observed fusing in pairs in the ascogonium. 



These fusions are to be observed in ascogonia of various ages, sometimes 

 when the investment of the ascogonium has only just begun, but usually at 

 some stage between investment and the emptying of the ascogonium. 

 There thus appears to be no definite stage of fusion for all the nuclei 

 corresponding to that of Pyronema, but a gradual fusion in pairs takes 

 place as development of the ascogenous hyphae proceeds. The majority 

 of fusions were observed when the ascogonium was partly emptied of its 

 contents, as the nuclei are then not so deeply crowded as in earlier stages, and 

 the cytoplasm does not stain so deeply. 



The nuclei in most stages are so close together that it is usually impossible 

 to distinguish from mere accidental contact the contact of nuclei which is a 



