Campbell, — Shi dies on the Araceae . 679 
that there is no marked departure from the usual course 
of development. Whether the embryo-sac mother-cell arises 
at once from the primary archesporial cell, or is formed after 
division of the latter, could not be determined. 
The apical part of the nucellus persists as in Aglaonema y 
but is perhaps a little larger, relatively. In the youngest case 
met with (Fig. 36) the primary nucleus of the embryo-sac had 
already divided, and the daughter-nuclei, which were placed 
at opposite ends of the sac, were dividing, the division of the 
two taking place simultaneously, and the embryo-sac at this 
stage presented the usual appearance. 
No attempt was made to follow in detail the development 
of the sac up to the time of fertilization, as it was evident 
that it was in no way peculiar. The three cells of the egg- 
apparatus are nearly similar, and taper into the narrowed 
micropylar end of the sac. The polar nuclei are just above 
the three antipodal cells (Fig. 39), and their fusion into the 
endosperm nucleus is completed some time before fertilization 
takes place. In most cases observed, the fusion was com- 
plete. The antipodal cells are surrounded by distinct mem- 
branes, and while not noticeably conspicuous, are readily 
demonstrable. 
Owing to the small size of the nuclei the plant does not 
offer special facilities for studying the phenomena of fertiliza- 
tion, and no attempt was made to follow these in detail, 
although in several cases the sexual nuclei were observed in 
process of fusion. The process is evidently slow, and before 
it is complete the egg has increased perceptibly in size, and 
the pollen-nucleus, which is smaller than the egg-nucleus, 
becomes much flattened against the latter, with which it 
finally merges completely (Figs. 41, 44). The fusion-nucleus 
is not noticeably rich in chromatin, but has a conspicuous 
nucleolus. In the cytoplasm of the egg there are formed 
numerous small starch-grains which become larger before the 
first division occurs in the young embryo. These starch 
grains disappear during the early cell-divisions in the embryo, 
and are probably used in the formation of the cell-walls. 
3 A 
