216 Cook: DEVELOPMENT OF EMBRYO-SAC AND EMBRYO 
ment of the sac of Lz/zum and many other plants may accomplish 
the same result by absorption of the surrounding cells of the 
nucellus. 
A very pronounced sclerification was developed in the inner 
part of the epidermal cells just before maturity of the embryo-sac 
(f. 6-9, z1-13, 16). These cells separated readily from the 
underlying cells of the nucellus and from each other; often the 
microtome knife would tear them loose and pressure upon the 
cover-glass of a fresh preparation was usually sufficient to separate 
them. Although fertilization was observed but once(f. 76) and 
then the path of the pollen tube could not be traced, I am inclined 
_ to believe that it occurs in the usual manner. 
DEVELOPMENT OF THE EMBRYO 
The embryo becomes very prominent (/: 76) and divides by 
a transverse division which is usually oblique (f. 22, 23). This 
is followed by the formation of a quadrant (f. 23) and an octant 
(7. 24), the embryo retaining its spherical form. In one 
instance a distinct twelve-celled embryo (f/f. 25) was observed. 
The formation of the octant is not always regular and the divisions 
following this are very irregular, especially in NW. advena, but the 
embryo retains its spherical condition until fully half developed 
and becomes free in the sac (f 26, 29). The free spherical 
condition corresponds to the condition observed in Nelumbo by 
Lyon (9). 
In one case polyembryony (f. 27) was observed and was 
apparently due to the splitting of a very young embryo, since the 
embryo may typically be said to have two or four basal cells, 
while in one case of polyembryony each embryo showed one dis- 
tinct basal cell. ; 
When well advanced there is an increased activity in the division 
of the cells on the side of the embryo farthest from the micto- 
pyle (f 29, c). This is the first appearance of the cotyledon 
the growth being forward and lateral, the edges being slightly 
curved so as to form a sort of elongate tray with the main spher- 
ical part of the embryo placed at one end (f. 30, 37). 
A few cells next to the micropyle, probably the original basal 3 
cells, show increased activity shortly after the first appearance of 
