782 Campbell.—The Embryo-sac of Pandanus. 
(or nuclei). Figs. 23, 24, p. n. y PI. LX, show the antipodal cell containing the 
polar nucleus projecting into the cavity of the embryo-sac. The inter¬ 
mediate stages between this condition and that where the nuclei lie free 
within the cavity of the embryo-sac were not seen, but as there were in no 
cases any free basal nuclei in such stages as those shown in Figs. 23 and 
24, it seems pretty certain that the nuclei of these protruding antipodal 
cells are ultimately discharged into the cavity of the sac. The number 
of the basal polar nuclei varies from a single one to six or more. Most 
commonly there seem to be two or three, and the number is probably to 
some extent governed by the number of antipodal cells. There was no 
evidence that the increased number of polar nuclei was due tp a division 
of the primary ones, although, of course, there is a possibility that such 
is the case. 
At the time of fertilization the much enlarged embryo-sac shows 
a pretty well marked egg apparatus at the upper end, while at the chalazal 
end (Fig. 25) there may be seen a somewhat flattened mass of antipodal 
cells, in this case about sixty-four. The lowest antipodal cells are still 
turgescent and contain a good deal of granular cytoplasm, but the other 
ones appear collapsed and have very little contents, looking as if they were 
disintegrating. Some of these cells may perhaps be those from which the 
lower polar nuclei have been discharged. 
Above the antipodal cells at the time of fertilization there may be 
seen a group of large nuclei closely crowded together, and beginning to 
fuse. As we have already seen, the number is usually from two to six, and 
it is quite impossible to tell which of these is the polar nucleus derived from 
the upper end of the sac, and which nuclei originated from the antipodal 
region. These nuclei subsequently fuse into a single large endosperm 
nucleus. 
Fertilization. 
The entrance of the pollen-tube into the embryo-sac was seen in 
a number of cases, but no satisfactory study of the details of fertilization 
could be made out. The pollen-tube is small, and could in some cases 
be seen forcing its way between the cells at the apex of the nucellus, but in 
no case were the nuclei satisfactorily shown, and although it is probable 
that there are, as usual, two generative nuclei, this cannot be positively 
asserted. Where the end of the tube could be seen within the sac, one 
of the synergidae, as usual, was destroyed. Presumably one of the 
generative nuclei is discharged into the sac, and small nuclei were sometimes 
seen in the neighbourhood of the recently fertilized egg which might 
possibly have been the generative nuclei, but it was quite as likely that 
these small nuclei were really derived from some of the nucellus cells 
which had been cut in sectioning the ovule. Nor were any satisfactory 
