SPECIAL NUCLEAR PHENOMENA. 33 



With the growth of the ascogonium the egg-nucleus divides and the 

 daughter nuclei become successively larger with the increasing size of 

 the cells in which they lie. This growth continues till the ascogonium 

 and ascogenous hyphse reach their full development, as described above. 



The nuclei appear at this stage in pairs in all the cells of the asco- 

 genous hyphse which are destined to produce asci (figs. 28, 29, 31-33). 

 The question as to the probable relationship of these nuclei has been 

 discussed above. There is no such arrangement for preventing the 

 inclusion of sister nuclei in the ascus as I have described for Pyronema 

 (40). On the other hand, the ascogenous hyphse are multinucleated 

 before cell division occurs, and there is no direct evidence that the 

 nuclear pairs are formed by the division of a single nucleus. 



The structure of these larger nuclei (figs. 31-33) appears to be the 

 same as that of the sexual nuclei just described, but owing to their 

 greater size the details can be made out with greater definiteness. The 

 relations of the central body and nuclear content come out much more 

 sharply, and it is possible to count with some certainty the number of 

 chromatin strands which extend into the nuclear cavity from the central 

 body. The nucleole stains bright red with safranin and is frequently 

 flattened somewhat against the nuclear membrane, even tending, at 

 least in fixed material, to break through it (figs. 31, 33) . The flattened 

 disk-like form of the central body, as it lies pressed against the nuclear 

 membrane, can be clearly made out. Its appearance and staining reactions 

 are the same as I have already described (38) for the central bodies of 

 other mildews and Discomycetes. With the triple stain the chromatin 

 shows a bright-blue color and the central body is reddish or violet. 



The strands of chromatin are regularly attached to the central 

 body, and from this point they extend into the central cavity of the 

 nucleus, forming a sheaf of diverging rays. The series of threads as a 

 whole produces distinctly the effect of a cone or bundle of rays extend- 

 ing from the central body into the cavity of the nucleus (figs. 31-34). 

 The bundle is broader or narrower, according as the threads diverge 

 more or less rapidly from their point of attachment. In some cases the 

 outer rays may follow more or less closely for some distance the inner 

 surface of the nuclear membrane, and the whole system of threads may 

 thus be distributed quite evenly through the nuclear cavity. In this 

 case the appearance of a cone or bundle of threads diverging from the 

 central body is partially lost, but the orientation and attachment of 

 the threads on the center is distinct and definite. In the majority of 

 cases, however, in this stage the threads form, for some distance inward 

 from the center, quite a definite diverging bundle (figs. 33, 34) . If we 



