Martin—Taphrina Coryli Nishida on Corylus. 
347 
cells. Miss Adams (1915) and Miss Bitner (1915) found the 
binucleate condition only in ascogenous cells, where they found 
evidences that pairing of cells had taken place. It seems very prob¬ 
able, however, from my observations, that the binucleate condition 
which is later observed in the ascogenous cells has arisen in the 
vegetative cells (fig. 6, 7), although by what process, I am unable 
to determine. 
As the fungus travels outward between cells of the palisade layer, 
the hyphae appear similar to those previously described, but the 
cells are usually longer and thinner. But as the mycelium passes 
between the epidermal cells, it becomes more difficult to determine 
the character of the vegetative cells, for they are only rarely seen 
and those observed become very slender as they force their way 
between the epidermal cells. Slender vegetative hyphae are also 
found in the cortex of the one-year-old twigs. 
The Ascogenous Cells and Nuclear Fusion 
By the time the fungus has reached the region between the epi¬ 
dermal cells and the cutin of the leaf, its cells have become much 
thickened and, being packed together, have become cuboidal in 
form. At times these fruiting or ascogenous cells are found in 
layers two or three cells thick, but as the outer layer develops, 
the cuticle is ruptured, the fungal cells increase in length and form 
asci. In the ascogenous cells, the cytoplasm is often more vacuolate 
than that of the vegetative cells, though this condition may vary. 
The binucleate condition which arose in the vegetative cells appar¬ 
ently does not continue long in the ascogenous cells, for most of 
these cells have only one large, fusion nucleus. 
Nuclear fusion is found quite often in ascogenous cells of ma¬ 
terial collected at any time of day, but in material collected early 
in the morning the nuclei in the majority of ascogenous cells are 
fusing. It may be that moisture and low temperature stimulate 
the activity of the cell in such a way as to favor nuclear fusion. 
The two nuclei approach each other (figs. 6, 7), finally lying side 
by side in the cell (fig. 8). Their nucleoles (one in each nucleus) 
are at first some distance apart, but the thickened chromatin masses 
lie close together. As the two nuclei come into contact with each 
other, the nuclear membrane breaks down between them, so that 
there is formed a large double nucleus (figs. 9, 10, 11). The two 
chromatic systems remain separate for a time as described by 
