38 BOTANICAL GAZETTE [juLY 
of Lilium, and as is familiar to all who have seen mitoses in the 
embryo-sac of Lilium and similar forms, is another argument in 
favor of this theory. 
The asters arise at opposite poles of the nucleus, but not. 
simultaneously. Serial sections of a large number of nuclei 
were examined before this conclusion was reached. We can 
hardly understand Davis’s (7) statement that in his studies he 
‘has never found a nucleus with a clearly defined solitary aster 
beside it. This is a very important point and the search was 
persistent.” In our own preparations of the second and third 
mitosis we never found anything but the solitary aster in the 
earliest stages. In studying this point, reconstructions were 
made from thin sections, and series were cut thick enough to 
include the entire nucleus. It is true that the first aster does not 
usually reach its fullest development before one appears at the 
opposite pole. In figs. rg and r5 and also in fig. zg (third 
division) there is only one aster. However, the second aster 
usually appears before development has proceeded so far. In 
spite of the fact that the two asters do not arise simultaneously 
we can confidently support Davis’s (7) conclusion that the two 
asters do not arise by the division of a single one. We found 
only two preparationsin which the asters were less than 180° apart, 
except in case of tripolar figures, which were not very rare (jigs. 
z6—third pole not shown—and 23). In early stages the two 
poles usually differ from each other in appearance, one pole being 
rather pointed and the other comparatively blunt (jigs. 27, 22) 
24,25). Cases like fig. 27 indicate that the blunt pole has been 
the last to develop. At this stage, neither pole is sharp, both 
being more or less rounded. The dome-shaped prominences OF 
‘‘caps,’’ as they may be called, are by no means easy to interpret. 
In some cases the cap looks like a mere extrusion of the nuclear 
membrane, while in others the nuclear membrane is still intact 
after the caps have become quite conspicuous. The rounded 
ends indicate considerable pressure from beneath. That the cap 
is something more than a structure built up by fibers radiating 
from the aster is shown by its appearance and by the fact that in 
transverse section it presentsa continuous line. The cap becomes 
