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the female gametophyte in nolana
373
semisolid carpel. The gynoecium is therefore held to be composed of
two whorls of five carpels and each nucule to be formed of a sleril
carpel conjoined with half the fertile on each side» and further (p. 430):
»The partial fruits, nucules, shows partitioning of the loculus in such
a way that each ovule lies in a separate chamber as in the crucifer
Bunicis Iirucago but the partitioning is caused by the tissues of the sterile
carpels».
The ovules are borne on the placenta, they have a massive single
integument, which encloses a small nucellus that consists of one cell
layer surrounding a single archesporial cell. By unequal growth of the
integument Ihe ovule becomes the appearance seen in Figs. 1 and 2.
The micropyle points downwards and is very long. A strand of
conducting cells ends at Ihe chalaza.
The archesporial cell becomes directly the functional megaspore
mother cell, which gives rise lo a normal telrade of megaspores in an
axial row separated by definite cell walls. The chalazal megaspore is
found to be Ihe functional one, Ihe other three are gradually
disintegrating (Fig. 3). The megaspore enlarges and after Ihree divisions of
the nucleus an eight nucleated embryo-sac is formed (Figs. 4—6). By
the time of embryo-sac development, Ihe nucellus epidermis has
degenerated, so that llie embryo-sac is in immediate contact with Ihe
integumentary tapetum, that has arisen in the meantime.
The appearance of the embryo-sac is seen in Fig. 7. It is broader
in its middle part and tapers towards the ends. The part of the
embryo-sac facing Ihe funiculus forms a right or slightly concave line whereas
the opposite side forms a fairly convex one. The two synergids are
densily filled with cytoplasm at their micropvlar ends and each has a
large vacuo! al ils lower end. The Ihree antipodals are of short duration.
They seem lo persist up to fertilization and Ihe primary endosperm
nucleus is situated in the neighbourhood of the egg cell, that has a
pear-like shape. The embryo-sac is heavily vacuolized and the
cytoplasm is accumulated around Ihe primary endosperm nucleus.
The pollen tube enters the ovule by way of the micropyle and
double fertilization is stated.
The post fertilization development presents some interesting
features. The formation of the endosperm begins before the first division of
the zygote. The primary endosperm nucleus divides about in the middle
of Ihe embryo sac and the division is immediately accompanied by the
formation of a transverse wall (Fig. 8). In Ihe micropvlar cell a
longitudinal wall is then formed and in Ihe chalazal cell a transverse one
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