182 Mottier.—Nuclear and Cell Division 
plasma-membrane is a uniform plane which in section appears 
as a smooth line. 
The cell-plate is not always laid down everywhere simul¬ 
taneously, but sometimes it appears at first more marked 
at the periphery. This seems to depend upon the position 
of the nuclei. 
It must be admitted that this process of cell-plate formation 
is very different from what takes place among the higher 
plants, where we have a plasma-membrane formed by the 
connecting fibres. If there be kinoplasm present, it does 
not exist in the form of visible fibres, such as connecting 
fibres, but what is really seen, seems, in part at least, to be 
a direct transformation of the walls of the alveolae into the 
cell-plate. 
All of this does not prove, however, that kinoplasm is not 
present, or that it is not instrumental in forming the plasma- 
membrane, which, there are strong reasons to believe, is 
composed of this substance. 
Shortly before the cell-plate is marked as a continuous and 
somewhat irregular line, as described, the region in which 
it will appear is sometimes to be distinguished by the presence 
of fewer chloroplasts and somewhat finer meshes of the 
cytoplasm. The region stains more nearly like the kinoplasm 
near the nuclei, and when the plasma-membranes are formed, 
they also retain the gentian violet with greater avidity than 
the cytoplasm in general, especially if the fixing fluid were 
stronger in osmic acid. I have found it to be almost invari¬ 
ably true, both in pollen mother-cells and vegetative tissue 
of the higher plants, as well as in Dictyota , that in material 
fixed in the solutions stronger in osmic acid, e.g. solution A 
above, the spindle-fibres, or kinoplasm, stained a much deeper 
blue than when solutions weaker in osmic acid were used ; 
and it may be added that the secret in the use of the chrom- 
osmic-acetic solution is to determine the proper amount of 
osmic acid necessary to make possible the best differential 
staining. The conclusion, therefore, is not unwarranted that 
in Dictyota the cell-plates are formed by means of kinoplasm. 
