1897 ] THE LIFE HISTORY OF SAGITTARIA VARIABILIS 267 
Alisma Plantago, although there are some striking and important 
differences. 
2. The generative nucleus divides into the two sperm nuclei 
long before the dehiscence of the anther, making a three-nucle- 
ated pollen grain. 
3. In the eight-celled embryo sac the upper polar nucleus is 
by far the largest, and the point of contact and of fusion of the 
two polar nuclei is in the lower part of the sac, the fusion usually 
being completed before fertilization. 
4. During the fusion of the polar nuclei the centrospheres 
and nucleoli also appear to fuse. 
5- The three antipodal cells are usually surrounded by cell 
walls before fertilization, and the antipodal region, having:devel- 
oped unusually thick walls, retains its original size and contents 
even when the embryo is fully formed, projecting somewhat like 
a vermiform appendix beyond the limits of the enlarged sac. 
. After conjugation, the first division of the definitive nucleus 
takes place at about the time of the division of the oospore, 
and at this first divisiona cell plate is formed making a partition 
wall which completely separates the embryo sac into two parts. 
7. The lower endosperm nucleus divides once or twice, 
forming two or three free nuclei which enlarge enormously and 
Seem to disintegrate when the embryo is mature. 
8. The growth and curving of the embryo sac is practically 
all above the partition wall; and in this part the upper endo- 
Sperm nucleus forms many small free cells, those aggregated in 
the lower part, above the partition wall, finally being surrounded 
by cell walls and forming a sort of cap over the ap ~ the coty- 
ledon. 
9. The pollen tube expands as it enters the embryo sac and 
passes down on one side past one of the synergids, — ine 
_ pears at this time. 
ee Io. The two sperm nuclei bate enter the cee sac ain. 
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