194 BOTANICAL GAZETTE [MARCH 
are almost entirely without vacuoles and the position of their nuclei 
is irregular (fig. 7). The antipodals are usually evanescent. 
The male gametophyte 
The stages-of pollen tube formation and of fertilization were 
not observed, and this fact, under ordinary circumstances, might 
have led to the belief that the form was parthenogenetic. This 
makes peculiarly fortunate the precaution which was taken early 
in the season, of preventing pollination in some of the pistillate 
catkins. As has been described previously, this was accomplished 
by covering with paper sacks seven of the twigs bearing pistillate 
flowers before pollen began to fly. Although each of these twigs 
bore about five catkins and each catkin contained several pistils, 
there was not a single case of seed formation observed. One may 
safely infer that parthenogenesis is not of usual occurrence in this 
orm. 
The endosperm 
The fusion of the polar nuclei and male cell was not observed, 
but must have occurred about April 15. Material killed on this 
date showed the eight-nucleate sac, but material killed on April 
16 showed the large endosperm nucleus. It may be that division 
of this nucleus did not take place immediately, since all the mate- 
rial examined within the five days following this shows it undivided. 
Material killed on April 22 showed two free endosperm nuclei. 
After this, the simultaneous free nuclear division goes on rapidly, 
so that by the time the division of the fertilized egg occurred there 
were sometimes as many as 35 of these parietally placed nuclei to 
be seen in a single section (fig. 8a). The increase in size of the sac, 
due to growth of the ovule itself, and the breaking down of tissues 
about the sac and especially below it was very great. By May 10 
the endosperm was seen as a very thin layer of cytoplasm about 
the embryo sac, which extended over three-quarters of the length 
of the ovule, which itself measured as much as 6 mm. About this 
time the formation of walls in the endosperm began, and this was 
followed by a centripetal growth of tissue so regular as to give the 
endosperm the appearance of being made up of plates of cells. 
These cells were large and contained unusually large nuclei. This 
