7 7 8 Campbell ’— Embryo-sac of Pandantes. 
the chalazal region could not be determined. Several cases, one of which is 
shown in Fig. 12, PL LIX, had six chalazal nuclei, but it could not be deter¬ 
mined which of the four nuclei of the preceding stage gave rise to the two 
extra nuclei. There is some uncertainty as to the subsequent divisions by 
which the number of chalazal nuclei increase to eight, and finally to twelve. 
Usually, at least, there are finally twelve of these chalazal nuclei, although 
it is possible sometimes there may be only ten. There is some variation 
in the form of the lower end of the embryo-sac, which may be either some¬ 
what pointed, or broad and rounded (see Figs. 14 and 15). 
In the oldest stages that were secured in P. Artocarpus , the embryo- 
sac, which had increased materially in size, showed at the somewhat narrower 
micropylar end two nuclei, while at the chalazal end there were twelve 
large nuclei surrounded by a large mass of granular cytoplasm containing 
several conspicuous vacuoles (Figs. 14 and 15). A similar, but smaller, 
mass of cytoplasm surrounds the nuclei at the upper end of the sac, and 
the large central vacuole is bounded laterally by a rather thick layer of 
cytoplasm which, however, contains no nuclei. In most cases there was 
no apparent differentiation of the cytoplasm at the upper end of the 
sac, although in a few instances there was a slight indication of what 
looked like the separation of an egg-cell and synergid; but this was very 
vague. 
Corresponding to the enlargement of the embryo-sac there is a marked 
increase in the size of the nuclei, which at the same time show a distinct 
reticulum, while in the younger sac the contents of the nucleus appear more 
uniform. The nucleolus is very conspicuous. In P. Artocarpus the increase 
in size is more marked in the chalazal nuclei than in the micropylar ones, 
which are noticeably smaller. In the most advanced stages found in 
P. Artocarpus the arrangement of the nucleus is very similar to that 
described by Johnson for Peperomia hispidulap except that there are 
fourteen instead of twelve chalazal nuclei in the latter, and these ultimately 
fuse into one enormous endosperm nucleus. 
Owing to the similarity of the nuclei in the nucellus cells adjacent to 
the young embryo-sac, and those of the sac itself, the former may be 
mistaken sometimes for nuclei belonging to the embryo-sac, but in the 
later stages the greater size of the embryo-sac nuclei usually makes it 
easy to distinguish them. There is sometimes found a small cell (Fig. 13,7), 
apparently cut from the side of the embryo-sac, as occurs in the embryo- 
sac in Peperomia . The contents of these cells are densely granular like 
the cytoplasm of the embryo-sac, but the nuclei are small, and it is quite 
likely that these small cells really belong to the nucellus. The occasional 
occurrence of small nuclei apparently free in the cytoplasm of the embry^o- 
1 Johnson, D. S.: A New Type of Embryo-sac in Peperomia. Johns Hopkins University 
Circular, 1907, No. 3, pp. 19-21. 
