94 BOTANICAL GAZETTE [ FEBRUARY 
may be in close contact with the wall of the spore; the resulting 
division gives again the characteristic difference in the size of 
the cells. In this case, however, the plane of the spindle is usu- 
ally in the plane of the long diameter of the spore. 
With the orientation of the microspore spindle so fixed as it 
is in these plants, it is easy to explain the dissimilarity in the 
size of the resulting cell-bodies. In this division, moreover, 
there is evidently equal division of the chromatin, as there is in 
all normal karyokinesis. The smaller nucleus resulting can have 
nothing to do with the chromatin content, and must depend upon 
its relation to the smaller cell body. From the zoological point 
of view, unequal segmentation as a factor in diffentiation is 
fundamental, and various speculations have been entered upon 
as to the cause of unequal division of the cell-body. Wilson’ 
prefers Conklin’s* view, that the cause lies in some relation 
between the karyokinetic figure and the cell body in which it lies. 
The inequality in the sizes of the nuclei in the pollen grain, more- 
over, might be explained largely from the unequal cell divisions. 
In those cases, however, of division in the microspore where it is 
reported that no cell wall is formed, we must assume that at 
least a transient plate or membrane must be formed in order to 
regulate the sphere of activity about each nucleus, and hence, 
probably, the size of each nucleus. 
In Symplocarpus there was no division of the generative 
‘nucleus in the pollen grain. Germinated pollen was obtained in 
a few hours by sowings on pith in 3 per cent. sugar solution. 
On a moist day I also found germinated pollen in the bract of 
the flower, but this is unsatisfactory to work with on account of 
the difficulty of taking it through the embedding process. I did 
not secure spindle stages in the division of the generative cell, 
but enough was secured to Show that division occurs soon after 
the nucleus passes into the pollen tube. The vegetative nucleus 
usually passes into the pollen tube first and does not deteriorate 
until after the division of the generative cell. The generative 
’ The cell in development and inheritance 275, : 
® The fertilization of the ovum. Biol. Lect. Marine Biol. Lab. Boston, 1894. 
