339 
Campbell . — Studies on the Araceae , III. 
were largely transverse, but in the specimen shown in Fig. 42, which seemed 
to be perfectly normal, there were several embryo-sacs lying side by side. 
The exact number is difficult to determine, and it is not always possible to 
decide whether the division-walls are not in some cases of secondary origin, 
and formed within the embryo-sacs themselves. 
Each young embryo-sac begins to develop — that is, divisions of the 
nucleus, and perhaps, sometimes, cell-divisions as well, occur. This makes 
it extremely difficult to decide how much of the cell-complex found in the 
centre of the nucellus is the product of a single embryo-sac (see Figs. 42, 43). 
It seems probable that one sac finally crowds out the others, but, on the other 
hand, it looked sometimes as if the structures present at the time of fertiliza- 
tion were the combined products of two or more of the primary embryo-sacs. 
In no case observed did the mature embryo-sac show the typical 
structure found in most Angiosperms. Sometimes a nearly normal egg- 
apparatus was found, but in such cases the other structures of the sac were 
not of the usual type, either there were no antipodal cells, or else no polar 
nuclei were developed. Indeed, so great was the variation, that it was 
quite impossible to make out any prevailing type, and all that can be done 
will be to describe the most striking forms met with, without attempting to 
decide what may be considered as the normal type. 
The simplest case observed (Figs. 48-50) had a single well-defined 
embryo-sac with two nuclei, one at each end. The upper nucleus was in 
the early prophase of division, it was large and conspicuous, and was sur- 
rounded by a clearly marked mass of cytoplasm, looking like the egg-cell 
of a typical embryo-sac. At the antipodal end of the sac was the second 
nucleus, surrounded by a similar but larger mass of granular cytoplasm 
like that at the upper end of the sac. The antipodal nucleus was in process 
of division. The nuclear plate, with about fifty-six chromosomes, was 
extremely conspicuous, and the nuclear spindle was very clear. 
What would have been the future history of this embryo-sac can only 
be conjectured, but it may very well represent an earlier stage of such a 
sac as that shown in PI. XVII, Fig. 52, where there was at the apex an egg- 
apparatus consisting of the usual two synergidae and the egg-cell, while at 
the opposite end of the sac there was a single large nucleus embedded in 
a mass of granular cytoplasm, suggesting a single large antipodal cell. No 
other nuclei were present, and it looks as if the polar nuclei were quite 
absent. A condition similar to this has been found in Aglaonema k 
In the sac shown at Fig. 44 there was a single large nucleus at the 
apex, and at the antipodal end there were apparently three nuclei. The 
latter were not noticeably different from the nuclei of the adjacent nucellar 
cells, and it is possible that they may have belonged to these and not to 
the embryo-sac itself. 
Campbell, loc. cit., II, Fig. 23. 
