394 
CLIFFORD H. FARR 
depth has been reached. Thus far no instance of bipartition by fur- 
rowing has been established in the higher plants, such as is so common 
in the animal kingdom. In the latter it is evident that the centrosomes 
are much smaller and much farther apart than are the nuclei in these 
mother cells, and hence if these centrosomes be the attraction centers, 
a resultant of forces might lead to complete bipartition. If, however, 
in these pollen mother cells the nuclei are the attraction centers, it 
may be that they are too large and too close together to accomplish 
complete partition in a binucleate cell. That the nuclear membranes 
are probably important in furrowing is indicated by the fact that fur- 
rowing is not resumed until the nuclear membranes are reformed in 
the telophases of the homoeotypic mitosis. 
Agricultural and Mechanical College, 
College Station, Texas 
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