Allen—Spermatogenesis and Apogamy in Ferns. 27 
A slightly later stage is shown in figure forty-five. The cells 
are united along one side hut are still distinct through more 
than half of the surface of contact between them. The two 
cells are rounded except along the edges of the surface of con¬ 
tact. A broad lobe from one nucleus extends into the other 
cell and lies in contact with its nucleus. It is doubtful whether 
there is yet actual continuity between the two nuclear cavities. 
The chromatin here is distinctly reticulate. There are a few 
uniform threads of chromatin—but there is also a real mesh- 
work with small aggregations of chromatin at the angles. 
It is plain from figures forty-four and forty-five that the 
chromatin is not always at the same stage at the time of fusion. 
In figure forty-four the chromatin is in practically the spirem 
stage. In figure forty-five it is in the earlier stage of the 
reticulum. The beginning of fusion is not dependent upon any 
particular condition of the chromatin. 
Further, the sixteen cells, although formed at the same time, 
do not always fuse simultaneously. In the spore sac from 
which figure forty-four is drawn, in the case of one or two 
pairs of cells the fusion was fairly well advanced; in some 
others it was about half completed; and in the one drawn it 
was just beginning. In all of the nuclei in this spore sac the 
chromatin is in nearly the same condition, consisting of fine 
threads of uniform diameter. In general, however, the reticu¬ 
late condition of the chromatin predominates in the earlier stage 
of fusion and the spirem is more common in the later stages. 
In figure forty-six, we have a slightly more advanced stage of 
fusion. The nuclear cavities are in communication and the 
cytoplasm of the two cells is almost completely fused, although 
along the left hand side of the figure the cytoplasmic masses 
are not yet in contact. The chromatin is reticulate and no nu- 
cleoles are present. 
It is noteworthy that although the stage of fusion in figure 
forty-six is somewhat more advanced, the fusion cell appears to 
be distinctly smaller than in either of the two preceding figures. 
As noted above, the drawings are all made on the same scale. 
This difference in size is probably due to the fact that the time 
when fusion begins, varies, and the spore mother cells are grow- 
