376 The Botanical Gazette. [October, 
Flowers of Acer rubrum in earlier stages of development — 
may be obtained in winter and early spring, by removing the 
scales and fine silken hairs that enclose them in the bud — 
From buds taken in the latter part of March (the same condi- 
tion may be found earlier), the ovules in the young female — 
flower were in the stage of development represented in fig.1. _ 
In the apex of the nucellus will be found a cell a 
larger than the other cells, and with more densely stained — 
contents. This is the mother-cell of the embryo-sac. At — 
the time work was begun upon this subject I was unableto — 
find flowers with younger ovules. The mother-cell, in all — 
probability, arises from a single hypodermal cell, but as 4 
growth proceeds it soon becomes more deeply situated in the a 
nucellus by the multiplication of the epidermal cells by tam 
gential or periclinal divisions (fig. 2). A transverse section of 4 
the nucellus in this stage of development is shown in fig-3 J 
the larger central cell with large nucleus being the mother- _ 
cell of the embryo-sac. This cell which has now elongat i 
considerably divides by a wall at right angles to its eet : 
axis (fig. 4). The upper cell divides again ina stots oat E 
ner, so that there are three cells resulting from the a . 
cell (fig. 5). The lower one of these three now en at 
gradually absorbing the two upper; its large nucleus — bad 
vides, and the resulting nuclei move away from eac yas 
toward opposite ends of the cell (fig. 5). The f 
known embryo-sacs of angiosperms. The embryo- 
ually increases in size at the expense of the tissue 
nucellus immediately surrounding it. 
The mature embryo-sac is broad at t 
but narrows gradually toward the antipodal ae her 
occupied by the small antipodal cells (fig. 8). we in the 
almost all plants, one sees a considerable vec oe 
position of the endosperm nucleus. It may nates 
egg-apparatus (fig. 9), or more nearly midway saplast lin- 
ends, but always imbedded in the layer of bn sac being 
ing the interior of the sac, the central cavity “ a noweveh 
occupied by one or more large vacuoles. ert 
the antipodal cells remain very small and t . 
be demonstrated only with considerable difficu 
soon absorbed after the embryo-sac ! 
the time increasing rapidly in size, espe 
effected. 
of the 
