414 BOTANICAL GAZETTE [JUNE 
In view of all the evidence, I cannot escape the conviction 
that the first division that occurs in the archesporium of the 
mature nucellus is quickly followed by a second division without 
the previous reorganization of the nuclei of the first division, 
and that this results in the four-nucleated embryo sac. 
Not only does the space of two days seem sufficient for the 
transition from the one-celled to the four-celled stage, but in 
some instances development had exceeded this. It was in 
material collected June 7 that I found the most satisfactory 
illustration of the eight nuclei of the sac (fig. 32). Here the 
synergids and oosphere are in the micropylar region, the three 
antipodals in the base of the sac, and the polar nuclei in the act 
of fusing in the middle region. In this instance I find no evi- 
dence that the pollen tube has made its approach, yet in view of 
its elusive character it would be unsafe to affirm that it has not 
done so, Several cases of the fusion of the polar nuclei were 
observed, but the presence of the antipodals was usually a mat- 
ter of doubt. This, however, is to be expected, when we con- 
sider the usual ephemeral naturé of these cells, and since their 
nuclei possess no character which distinguishes them from the 
nuclei of the disintegrating cells of the nucellus, it is not an 
easy matter to identify them. 
About the time the four-celled stage is reached, the embryo- 
sac begins to enlarge rapidly at the expense of the nucellar 
tissue, and by the time of the fusion of the polar nuclei, or 
soon after, the nucellus has almost entirely broken down. There 
is usually a fragment of the nucellus extending from the chalazal 
region a short distance up one side. This gives to the embryo- 
sac a somewhat pointed base, which is the only structure observed 
suggestive of the so-called caecum. 
The synergids crowd well up into the micropyle, and display 
that striated beaked structure noted by observers in some other 
plants. Fig. 34 in no way exaggerates the prominence of these 
striated tips, and, as Chamberlain observed in Salix, these tips 
may persist for a considerable time as a plug in the micropylar 
end of the sac. 
