Peng etre ae Tee 
é 
1906] SHREVE—SARRACENIA PURPUREA i ee 
EMBRYO. 
The first division of the fertilized egg is in a direction parallel 
with the length of the sac. The two-celled embryo (fig. 43), at first 
oval, becomes gradually elongated, divisions following in the same 
plane as the first, but not in a manner in which it has been possible 
to discover any regularity. After the embryo has attained a length 
of five to seven cells, there is a lateral division of the terminal cell 
(7g. 44), the beginning of the embryo proper. The suspensor is 
. usually curved, though not always to so great an extent as shown 
in the figure. I have been unable by lack of material to observe 
Stages in the development of the embryo immediately following the 
transverse division of the terminal cell. 
In material of June 25 the embryo proper is found to have reached 
a size of approximately 250 cells, with ellipsoidal form (fig. 45). 
Dermatogen and periblem are well-defined, but no procambial cells 
have as yet appeared. The endosperm has by this time increased 
greatly in diameter, encroaching upon the tissue of the integuments. 
The endosperm cells have become well-stored with aleurone except 
in the central portion of the micropylar end—the region destined 
to be occupied by the full-sized embryo of the mature seed. In 
embryos as large as that shown in fig. 45 the suspensor is surrounded 
by endosperm cells in which aleurone has been laid down; the 
embryo proper is surrounded by cells of highly vacuolated contents. 
SEED AND SEEDLING. 
Material gathered during the last week of July exhibits seeds 
Which are practically mature. The embryo has grown to an elon- 
gated ellipsoidal form, the cotyledons being about one-third the 
length of the whole (fig. 46). Elongated procambium cells stretch 
from the basal end of the embryo to the region of the stem growing- 
point. Stomata are not formed in the embryo until the time of 
germination. A few endosperm cells at the sides and cotyledonary 
end of the embryo are free of aleurone, as they remain in the mature 
seed. 
The surface layer of cells of the integument forms the seed coat. 
Its cells become irregular on their external surface and the walls 
are greatly thickened, with conspicuous pores in the lateral and 
basal walls, but none in the walls forming the surface of the seed 
