1906] SHREVE—SARRACENIA PURPUREA III 
marked by the time of the appearance of the mother cell. Both 
transverse and longitudinal sections (figs. 16 and 17) show a double 
layer of cells at the sides of the mother cell, and median longitudinal 
sections show approximately five rows of cells in the ovule, exclusive 
of the epidermis. 
The integument is single, its development beginning by periclinal 
_ divisions of subepidermal cells upon the convex side of the bending - 
ovule, and continuing as a ring which grows rapidly on the side 
where it began first and slowly on the opposite side, which lies next 
the raphe. The rapid growth of the ovule is accomplished largely 
by the chalazal end. By the time of the first division of the mother 
cell the bending of the ovule is completed, the integument has grown 
so as nearly to close the micropyle, and the mother cell has increased 
in size and encroached upon the nucellar tissue so as to lie next the 
epidermal cells over the entire distal end (fig. 20). 
The difference in the time of appearance of the ovules upon the 
different parts of the placenta causes a difference in the degree to 
which the integuments develop (fig. 19), and also a difference in 
the maturation of the mother cell, and the germination of the mega- 
spore in ovules in the different parts of the placenta, a difference 
which long remains evident. 
At the first division of the mother cell it was not found possible 
to count the number of chromosomes. The division is followed by 
the formation of a wall (fig. 20), and in about half the cases observed 
both the daughter cells again divide to form the normal linear 
tetrad of megaspores (jig. 23). In the remaining cases the micro- 
pylar daughter cell fails to divide, resulting in a series of three mega- 
spores (fig. 21); and much less frequently the micropylar daughter 
cell divides by a wall parallel or nearly parallel to the long axis of 
the nucellus (fig. 22). In any casc it is the chalazal megaspore which 
functions, the micropylar ones being appressed to the layer of nucellus 
and absorbed. The maturation of the megaspore is coincident 
with the tetrad division of the microspore mother cells. 
EMBRYO SAC. 
Such has been the elongation of the ovule by the time the megaspore 
matures that the nucellus is lengthened five or six times its diameter, 
