1898 | EMBRYOLOGY OF ALYSSUM 317 
undivided, but after fertilization takes place endosperm is formed 
very rapidly and is especially abundant around the proembryo, 
obscuring it and making it difficult to distinguish the early stages 
of embryonic development if the section was cut diagonally. 
DEVELOPMENT OF THE EMBRYO. 
The first division in the proembryo is transverse and cuts off 
a basal suspensor cell which does not divide again (fig. 13, 2). 
The cell at the end divides very soon into a terminal cell, a 
true embryo cell ( figs. 73, 74,c) and an intermediate cell ( figs. 
13, 14,6). The terminal embryo cell divides by a longitudinal 
wall into two cells (fig. 75, c), and the two following longitudi- 
nal divisions at right angles to the first cut it into quadrants 
(jig. z6, eh The third division is a series of transverse walls 
in the cells of the quadrant and produces an octant (/ig. 17, c). 
The dermatogen is the first tissue to be differentiated and is 
cut off from the octant by a series of periclinal and anticlinal 
walls (figs. 78,79). Division in the cells of the octant is evidently 
almost simultaneous, for I could find no instance where any one 
seemed to have priority in the process. The terminal embryo 
cell is now represented by two well developed tiers of cells 
(figs. 19, 20, ¢, da). In each tier, while the dermatogen divides 
radially, the inner cells undergo a longitudinal division. 
Meanwhile the intermediate cell (fig. 74, 4) has been divid- 
ing by a series of transverse walls, and in the cell next those 
derived from the terminal embryo cell ( fig. 79, ¢), the wall has 
become somewhat rounded. This cell divides, first into two 
and then into four cells by longitudinal walls, making a quad- 
rant. These divisions and the transverse divisions which follow 
and form the octant correspond to those which take place in 
the terminal embryo cell, and, since this cell develops into the 
lower part of the embryo, I shall henceforth refer to it as the 
basal embryo cell. The whole embryo is therefore developed 
from two original cells, a terminal embryo cell and a basal 
embryo cell, both of which first form quadrants by longitudinal 
walls, and subsequently octants by a series of transverse walls in 
