De rmaees Si MRT Synt Ace 
a ia aah cee ai 
es een 
“ 
ln 3S nose nye:., Sila 
1897 | THE LIFE HISTORY OF SAGITTARIA VARIABILIS 261 
side of the partition wall will be called the upper endosperm 
nucleus, and the one on the antipodal side of the partition wall 
the lower endosperm nucleus. 
The upper endosperm nucleus immediately begins to travel 
upward on the convex side of the embryo sac wall, and imme- 
diately begins a rather rapid free nuclear division (figs. 37, 38, 
39). At the same time the ovule takes on its campylotropous 
shape, the sac almost doubling on itself, and the elongation prac- 
tically all taking place above the partition wall (figs. 38, 47, 73). 
In the early stages the free endosperm nuclei are about equally 
distributed from the embryo down to the partition wall. After 
the embryo has reached nearly the mature condition the numer- 
ous free endosperm cells, which in the meantime have accumu- 
lated above the partition wall, begin an active process of free 
cell wall formation, forming quite a large cap, which extends 
over the tip of the cotyledon and crowds down upon the parti- 
tion wall, forcing its outer margin downward (/igs. 44, 73)- 
In the meantime no such process has been going on in the 
compartment below the partition wall. The lower endosperm 
nucleus does not divide for a long time, but increases consider- 
ably in size (fig. go). Its first division usually occurs at the 
time when the embryo is about seven or eight celled, and it is 
nearly always divided when the embryo is from nine to eleven 
celled. Sometimes one of the nuclei may divide again, thus 
producing three nuclei ( fig. 43), or it may be that the three nuclei 
were produced by direct division. No more than three nuclei 
were observed in any stage, although it is possible that some- 
times there may be more. These nuclei increase enormously in 
size, being as large or even larger than the giant nucleus of the 
vesicular suspensor cell. They are nearly always closely _ 
crowded together (ig. 43), and at the time of the free cell wall _ 
formation of the upper endosperm they appear to break up and 
_ take on the deep stain which is characteristic of the antipodal 
nuclei (fig. 44). When the ovule has reached maturity, a a 
be seen “ these nuclei is an pews, epede mass of cd 
Le | . ne ey rs chet 
- = 
