1900] DEVELOPMENT OF THE EMBRYO-SAC 29 
preparations were obtained illustrating this condition and repre- 
senting all stages up to the next division of the nuclei. As 
shown in the accompanying figure (jig. 8), the upper cell 
becomes gradually larger and more vacudlate, while the cyto- 
plasm of the lower stains more deeply and fills nearly the entire 
cell cavity. No cases were observed, however, where one could 
infer that either cell was in the process of disintegration. 
At a period shortly before the opening of the flower further 
changes occur, the first of which is the immense increase in size 
of the upper cell. The wall between the two still seems to 
remain intact, although becoming very thin and delicate. In 
some cases the wall is so delicate at this stage as to be almost 
invisible, and may have broken down entirely, in which case 
both cells would be merged into the general cavity of the 
embryo-sac, but in later stages two cells are again seen, All of 
the four nuclei undergo division simultaneously, resulting in the 
stage with eight nuclei, just as in Lilium (fig. 9). In several 
cases shortly after this two large nuclei were seen fusing near 
the lower end of the upper cell, while the lower cell contained 
the distorted remains of three other nuclei. The latter cell was 
thus apparently already in the process of disintegration. It 
seems probable that one of the four nuclei originally formed in 
the lower cell must have ruptured the thin cell-wall and fused 
with the upper polar nucleus after the normal manner. 
In fig. ro is represented an embryo-sac just prior to fertiliza- 
tion. At this stage the ‘‘ egg-apparatus ”’ consists of two syner- 
gids and the egg. The former lie close together, with the long 
axis more or less transverse to the axis of the embryo-sac, and 
are elliptical in shape, with the wall at the upper end thickened 
and densely striate. Just below these is the large egg nucleus, 
separated from the synergids and from the main cavity by very 
delicate cell membranes which seem to extend completely across 
the embryo-sac so as to join the lateral walls on either side. 
Below the egg-apparatus is the very large main cavity of the 
embryo-sac lined with a thin layer of cytoplasm. In this, near 
the base, is the large definitive nucleus still showing signs of the 
