146 ANDERSON: EMBRYOGENY OF MARTYNIA LOUISIANA 
to grow up as a ring enclosing a central ovarian cavity as is 
seen in cross section (Fic. 10, C). Ata very early stage in the 
growth of the pistil, two parietal placentae appear. These 
are seen as outgrowths from the walls of the cavity (Fics. 10 
and 11, L). These outgrowths extend toward the center of the 
cavity and soon each forms two lobes (Fic. 12, L) which develop 
into the two lamellae of each placenta, resembling in cross 
section the letter T (Fic. 13, L). The placentae grow together 
at the base, thus forming a short columella. A cross section 
through the base of the ovary would appear as two-celled, but 
no ovules are developed from this region of the placentae. The 
upper part of the pistil is tubular and more narrow, forming 
a long, slender, hollow style which terminates in an unequally 
two-lipped stigma (Fic. 15, H). 
DEVELOPMENT OF MEGASPORE AND EMBRYO-SAC 
The young ovule first appears as a small, nipple-like protub- 
erance upon the placenta. Very early in its development, a 
hypodermal cell near the tip becomes differentiated and may be 
distinguished from the surrounding cells by its large nucleus and 
dense cytoplasm (PLATE 7, FIG. 17). Thiscell, the megaspore 
mother-cell, grows rapidly, keeping pace with the lengthening 
nucellus. At this stage, the nucellus consists of merely the en- 
larged megaspore mother-cell, covered by the epidermis (FIG. 18). 
At the base of the nucellus the single integument appears as a fold, 
at first more pronounced on the side next to the cavity of the 
ovary (Fic. 18, 1). By the more rapid growth of this side the 
ovule soon becomes sharply curved, so that the long axis of the 
nucellus is now parallel with that of the funiculus. At this 
stage, the integument extends around the nucellus, which has 
become more elongated (Fic. 19). With further growth the 
integument soon equals and finally exceeds the nucellus (FIGs. 
20.and 21). The megaspore mother-cell has also grown rapidly 
and when fully developed is still enclosed by only a single layer 
of nucellus (Fic. 21). The nucleus, which has increased in 
size preparatory to the first division and which has had a posi- 
tion near the center of the cell (Fic. 20), comes to lie nearer the 
chalazal end, where it undergoes the first or heterotypic division 
(Fic. 21). All the spindles of this stage found were rather small 
as compared with the size of the cell. Whether cell formation. 
follows this first nuclear division was not ascertained, but the: 
