204 BOTANICAL GAZETTE [SEPTEMBER 
the thickening of the connecting fibers in the equatorial region to 
form a septum which separates the cells. This splits in the central 
region first, and often a thin layer of orange staining material is to 
be seen between the split layers. The plasma membranes formed 
by the splitting of the cell plate are made very conspicuous in cells 
in which there is a slight plasmolysis. The cell wall seems in most 
cases to be fully formed before the second division is completed. 
Several preparations were found in which the wall seemed to be 
incomplete after the second division (jig. 7). These, however, may 
represent a stage in the removal of the cell walls, as described 
below. 
In many cases the wall of the first division is transverse, but not 
infrequently it is oblique (figs. 4, 12). The walls formed in the second 
division are extremely variable as to their position. F requently 
(fig. 11) they are transverse, forming a linear row of four cells. 
Very often the outer daughter cell divides longitudinally and the 
inner transversely (jig. 8). Less frequently, the outer divides trans- 
versely and the inner longitudinally (jig. 6). Fig. 7 shows an arrange 
ment which is occasionally met with, both daughter cells having 
divided longitudinally. Rather frequently one section shows two 
cells divided transversely, while the next succeeding section shows 
two cells divided longitudinally (figs. 9, 10). This arrangement 
could only result from the division of the mother cell at first by 4 
longitudinal wall parallel to the plane of the section, and the division 
of one of the daughter cells by a transverse wall and of the other by @ 
longitudinal wall. This case is easy to recognize when the plane ° 
the section is such that both of the cell boundaries of the second 
division are vertical. It is much more difficult to recognize when one 
of the cell boundaries of the second division lies in or near the plane 
of the section. Such a mode of division is of course frequently 
found in pollen mother cells. Fig. 12 shows, however, by far the 
most common arrangement of the cells, in which the first wall * 
oblique and the walls of the dividing daughter nuclei are approxr 
mately at right angles to it. ‘ 
Most of these various arrangements of the four cells resulting 
_ from the division of the embryo sac mother cell have been desct! 
by other authors, but in the stages immediately following We ut 
ze ~~ 
