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1902] BINUCLEATE CELLS IN HYMENOMYCETES 13 
are regularly correlated with increased size in the cell to which 
the nucleus belongs. 
Fusion takes place generally when the basidium has reached 
from one-half to two-thirds of its mature size, though wide vari- 
ations from this rule may be observed. The process can be 
observed readily in all stages. The nuclei become flattened 
upon each other. The nuclear membranes disappear over the 
area of contact and the nuclear cavities become continuous. 
The fusion nucleus shows a constriction for some time around 
the area of union. This furrow gradually disappears and the 
nucleus is evenly oblong oval in outline. Later it becomes more 
spherical, regaining the shape which it had before fusion took 
place. 
Just how the chromatin masses are combined cannot be made 
out. They become apparently continuous in the region of con- 
tact as soon as the membranes have disappeared. Later no line 
of demarcation between the two can be made out. Still Iam 
inclined to believe that the appearances of homogeneity are not 
to be taken as conclusive evidence on this point. There seems 
little doubt that the nucleoles fuse. They are conspicuous, 
sharply defined objects clearly differentiated as clear red spheres 
in the blue chromatin throughout the whole process of fusion. 
Each of the nuclei before fusion appears with astonishing regu- 
larity as possessed of one nucleolus (figs. 2-4), and just as regu- 
larly the spherical fusion nucleus shows a single and frequently 
much larger nucleolus. During the earlier stages of fusion the 
two nucleoli are still present (figs. 5,6). They are frequently 
found later close together and pressed upon each other, though 
such figures as these are not to be considered as having great 
weight in view of the irregularity in shape which nucleoli fre-. 
quently show. The fusion nucleus increases still further with 
the further growth of the basidium. It lies generally in the 
mature basidium at about two-thirds the distance from the base 
to the apex. 
The stages in the division of the nucleus have been very 
fully described by Wager. They are abundant and easily found 
