a hed ie au) ome 
1898] THE LIFE-HISTORY OF RANUNCULUS 83 
decidedly different from the method of sac development in 
the monocotyls we have studied, in which the sac enlarges above 
the base, leaving the dwindling antipodals at the bottom of a 
pit-like depression, which sometimes is thrust to one side of the 
center. The one-sided development of the sac is determined by 
the fact that it is obstructed on one side by the conspicuous 
fibrovascular bundle, while the other side and bottom are directed 
towards the free cavity of the ovary. 
At this stage of development the endosperm nuclei, formerly 
distributed through the cavity of the sac, have assumed the 
parietal position, forming a complete lining layer, interrupted 
only by the embryo and the antipodal stalk. It will be noted 
in the figure last cited that the embryo has completed only the 
first division. 
The most interesting phenomenon in connection with the 
formation of endosperm, however, was the occasional evidence 
of its formation before the fusion of gametes, and even before 
the entrance of the pollen tube into the cavity of the sac. In 
#g. 58 a preparation is shown in which the large egg is lying in 
pe very apex of the sac, the two synergids being apparent in an 
adjacent section, and yet free endosperm nuclei are distributed 
through the sac, and are even assuming the parietal position. 
It does not follow, however, that the endosperm begins to 
ana any stimulus from the pollen tube.. The presence 
ube in the style is known to exert a strong influence 
"pon the adjacent tissues, which may well be felt in the embryo 
thew beginning of endosperm formation, therefore, even 
ais, served before the entrance of the pollen tube into the 
Wihien: a cued —— the less be definitely related to the phe- 
heh ertilization, of which the entrance of the tube and 
uston of the gametes are only a part. 
he Parietal placing of endosperm cells is a phenomenon of 
: eas deserves consideration. That the curving of 
and the mo € pollen tube towards the nucleus of the oosphere 
€na that aa of the male nucleus towards it are phenom: 
pend upon chemotropism seems to be a satisfactory 
Orien 
