148 BOTANICAL GAZETTE [AUGUST 
its coarser chromatin strands (fig. 18). In fig. 18 the three nuclei 
as a whole present a more or less globular contour, although the 
nuclear membranes are still present at the surfaces of contact. 
In Trillium grandiflorum the three nuclei, which unite to form 
the primary endosperm nucleus, are all alike in shape, it being 
impossible to distinguish the male nucleus from the two polar 
nuclei by its form or size (fig. 16). Since the mass of the three nuclei 
is so large, it is often impossible to find parts of all three nuclei in 
one section, and frequently only two will be visible (fig. 19). All 
three contain nucleoli, sometimes one, while at other times there 
are many. The chromatin strands thicken until they may be 
traced for a considerable distance (figs. 19, 20). While in some 
instances the membranes still separate the nuclei (fig. 20), at 
other times they are not visible, as in fig. 19; but, nevertheless, 
where the chromatin contributed by one nucleus leaves off and 
that of another begins is very easily seen. 
Up to the period when the spirem has assumed its mature 
thickness, the separating membranes may not have entirely dis- 
appeared (fig. 21), and in some cases the three groups of spirems are 
plainly evident. From fig. 22 it could be concluded that a complete 
fusion or intermingling of chromatin had previously occurred, but 
_ such has not happened, for in the next section of this same primary 
nucleus parts of all three nuclei are seen (fig. 21). Even at this 
stage, before the complete breaking down of the separating mem- 
branes, segmentation has begun and spindle fibers are forming 
about the group. As far back as the coming together of the two 
polar nuclei and the sperm nucleus, a surrounding complex of 
fibers could be seen (fig. 18). 
In fig. 21 the fibers have commenced to radiate out into the 
cytoplasm, followed after a short period by a complete segmenta- 
tion of the spirems, resulting in three groups of chromosomes being 
scattered upon the three arms of the tripolar spindle, respectively 
(figs. 23, 24). As the tripolar structure gradually assumes the 
form of a bipolar spindle, the chromosomes, which were previously 
lying upon the third arm, are pulled into line with the other two 
groups, thereby forming a typical bipolar spindle (figs. 24, 25): 
The chromosomes now thicken and are typically arranged into the 
