Campbell. — Studies on the Araceae. 671 
each is a potential embryo-sac, and its nucleus may undergo 
the first divisions ; but in no case observed was more than 
one complete embryo-sac seen. The secondary embryo-sac, 
where two are present, may persist, however, until the defini- 
tive embryo-sac has reached its full development ; indeed it 
is quite impossible sometimes to be certain whether the 
structures present at the time of fertilization are all the 
products of a single embryo-sac, or of two (see Fig. 11). 
Where two or three embryo-sac mother-cells are present, they 
are often quite similar, and as the nucleus may divide once or 
twice in all of them, it is impossible to determine which is 
destined to become the definitive embryo-sac. In Fig. 5 is 
shown an ovule where there are two entirely similar young 
embryo-sacs, each of which contains four nuclei. In another 
case observed (Fig. 7) there were three young embryo-sacs 
separated by oblique walls. In the upper one [a) there was 
a single large nucleus ; in the second ( b ) there were eight 
nuclei, in two groups of four, and the members of each group 
partially fused, in a manner entirely similar to the ordinary 
fusion of the polar nuclei. The lower sac ( c ) was apparently 
the definitive embryo-sac. There were eight (possibly nine) 
nuclei in this. Four of the nuclei w r ere enclosed by delicate 
membranes, and formed a group of Cells suggesting an egg- 
apparatus, or possibly a group of antipodal cells. Near these 
was a nearly hemispherical cell ( o ) whose nucleus was pre- 
paring to divide. This was near the upper end of the sac, 
but at one side. Near the base of the sac was a group of 
large nuclei, partially fused together, and presumably giving 
rise to the endosperm-nucleus. Three nuclei were very plainly 
seen, and there was possibly a fourth one, but this could not 
be certainly determined. Whether the two groups of 
nuclei in the second embryo-sac (b) were destined to take 
part in the endosperm formation, could not, of course, be 
determined. 
In the embryo-sac shown in Fig. 10 there were eight 
nuclei. Four of them were at one side of the sac near the 
apex, and there was some indication of the differentiation of 
