676 Campbell.— Studies on the Araceae. 
The embryo-sac in the ripe seed occupies relatively a small 
part of its bulk. The large development of the integuments 
and chalazal part of the ovule suggests the perisperm forma- 
tion of the Piperaceae or Cannaceae. 
The Embryo. 
The embryo may occupy the usual position at the micro- 
pylar end of the sac, but more commonly it is at some distance 
from the apex of the sac, corresponding to the lateral or even 
basal position of the egg-cell. 
The first divisions (Fig. 24) are probably always transverse, 
but no well-defined suspensor is developed, this doubtless 
being associated with the early filling up of the sac with endo- 
sperm, which completely invests the young embryo. The 
cell next the wall of the embryo-sac may be regarded as 
a suspensor cell, but it does not become enlarged, nor give 
any other evidence of being functionally important. 
The subsequent divisions of the embryo do not show an 
absolute regularity. The strikingly pointed form of the young 
embryo shown in Fig. 26 recalls the embryos of some Grasses ; 
but this does not appear to be by any means always charac- 
teristic of the young embryo of Aglaonema. 
As the embryo grows it assumes an elongated form, but for 
a long time there is no differentiation of the external parts, 
nor are the tissues at all clearly defined. The enlarging 
embryo encroaches rapidly upon the endosperm, and fills 
almost completely the upper part of the embryo-sac. The 
greater part of the embryo is composed of the cotyledon, 
which becomes somewhat club-shaped and expanded at the 
end, which crowds into the enlarged chalazal part of the 
embryo-sac, destroying the endosperm as it grows, and leaving 
but a small part of it intact (Fig. 33). The tissues of the 
embryo are almost perfectly uniform, and the boundaries 
of the different organs very vaguely defined. The hypocotyl 
is very short, and although a median section of the root-end of 
the embryo (Fig. 31) shows some slight differentiation of the 
primary tissues, this is very imperfect. In the older embryo 
