580 Dale. — Observations on Gymnoascaceae. 
filled with dense protoplasm, but in some stages, apparently 
the later stages, the protoplasm is vacuolated. 
At the time of fusion a considerable portion of the wall 
between the two cells breaks down, and the nuclei and proto- 
plasm become mingled. Doubtless a nuclear fusion now takes 
place, but this has not been determined with certainty (Figs. 
27 and 28). The nuclei pass over from the sterile cell into 
the ascogone (Fig. 28), and later into the prolongation of the 
ascogone (Fig. 16). Evidently they ultimately pass into the 
ascogonous hyphae, for, within a mass of ripening asci are 
to be seen ascogenous hyphae containing many nuclei, while 
the conjugating cells, though retaining their original shape 
and size, and often showing very distinctly the point of fusion, 
are completely empty (Fig. 29 a , b, and c). The numbers 
of nuclei in the ascogenous hyphae are so large that it would 
seem as if nuclear division occurred in these hyphae, more 
especially if we consider the enormous numbers of asci pro- 
duced from one pair of conjugating cells. The small asco- 
genous hyphae generally show one nucleus, with a nucleolus 
and nuclear zone, lying in the apex of the hypha, before 
it has begun to enlarge (Fig. 30 a). At a later stage when 
the apex is beginning to swell (Figs. 30 and 31) we find first 
two and then four nuclei which are smaller in size than the 
original nucleus, and apparently have no nuclear zone. 
In the stage with two nuclei, the nuclei in some cases 
lie one above the other (Fig. 30 b'\ and in other cases side 
by side (Fig. 30 b"), recalling the figures and descriptions 
given by Harper 1 and others of the development of the asci 
in the higher Ascomycetes. In Gymnoascus also the arrange- 
ment of the nuclei in two different planes may indicate that 
the nucleus has undergone two divisions. 
At a still later stage the ascus becomes larger and almost 
spherical, while, instead of being filled with dense protoplasm, 
it has a large central vacuole, so that the protoplasm and 
the eight nuclei it now contains, come to lie on the wall, 
1 Sexual Reproduction in Pyronema confluens and the Morphology of the Asco- 
carp, Annals of Botany, Sept. 1900, vol. xiv, p. 363. 
