354 BOTANICAL GAZETTE [MAY 
THE DEVELOPMENT OF THE EMBRYO SAC. 
The embryo sac arises from the lowest cell of an axial row of 
four cells, that is, from the cell most distant from the micro- 
pyle. The mother-cell of the embryo sac grows rapidly, soon 
becoming strongly differentiated from the surrounding cells. 
At some time during the early stages of development, the 
‘nucleus of the macrospore moves to the micropylar end of the 
spore and there divides. The embryo sac contains very little 
cytoplasm at this stage, with the exception of the dense mass 
around its nucleus (fig. z). It agrees in this respect with the 
young embryo sac of Silphium, as described by Merrell (1900), 
and differs from Lilium and some other plants in which the 
embryo sac is densely filled with cytoplasm at the time of the 
first nuclear division. 
In A. multifforus the young embryo sac reaches an advanced 
stage of growth at the time of the first division of its nucleus, 
and does not show a very great increase in size subsequent to its 
binucleate stage. In the other species studied, however, the 
embryo sac does not assume its ultimate form until about the 
time of the fusion of the polar nuclei. After the division of the 
macrospore nucleus, one of the resulting nuclei moves toward 
the opposite or lower pole. In the meantime the embryo ang 
continues to grow in length, but increases very little, if any, in 
breadth. At the time of the second nuclear division, the 
embryo sac is long and somewhat cylindrical in outline. Here, 
as in other angiosperms, the two nuclei divide simultaneously, 
the division occurring, in some cases at least, before the lower 
nucleus has reached the antipodal end of the sac (figs. 2,3): 
In the embryo sac shown in fig. 2 the second nuclear division 15 
just completed, and the nuclei have not as yet separated. The 
four nuclei enter the complete resting stage, as shown in KE. 3: 
and then immediately divide again, giving rise to a typical eight- 
nucleate embryo sac. 
At the time when the eight nuclei are formed, the embryo 
Sac, aS seen in vertical section, is more or less rectangular In 
outline, but from this stage on the two poles of the embryo sac 
may become strongly differentiated. The antipodal end shows 
