nsisting of two layers of
cells, becoming thicker in the middle of the section where the
single fibro-vascular bundle is seen (Fig. 81, _H_). On opening, the
cavities of the adjacent sporangia are thrown together. The inner
cells of the wall are marked by thickened bars, much as we saw in
the pine (Fig. 82, _A_), and which, like these, are formed shortly
before the pollen sacs open. The pollen spores (Fig. 81, _I_) are
large, oval cells, having a double wall, the outer one somewhat
heavier than the inner one, but sufficiently transparent to allow a
clear view of the interior, which is filled with very dense,
granular protoplasm in which may be dimly seen two nuclei (_n_,
_ni._), showing that here also there is a division of the spore
contents, although no wall is present. The spores do not germinate
very readily, and are less favorable for this purpose than those of
some other monocotyledons. Among the best for this purpose are the
spiderwort (_Tradescantia_) and _Scilla_.

Owing to the large size and consequent opacity of the ovules, as
well as to the difficulty of getting the early stages, the
development and finer structure of the ovule will not be discussed
here. The full-grown ovule may be readily sectioned, and a general
idea of its structure obtained. A little potash may be used to
advantage in this study, carefully washing it away when the section
is sufficiently cleared. We find now that the ovule is attached to a
stalk (funiculus) (Fig. 81, _G_, _f_), the body of the ovule being
bent up so as to lie against the stalk. Such an inverted ovule is
called technically, "anatropous." The ovule is much enlarged where
the stalk bends. The upper part of the ovule is on the whole like
that of the pine, but there are two integuments (i, ii) instead of
the single one found in the pine.

As the seed develops, the embryo sac (_G_, _sp._) enlarges so as to
occupy pretty much the whole space of the seed. At first it is
nearly filled with a fluid, but a layer of cells is formed, lining
the walls, and this thickens until the whole space, except what is
occupied by the small embryo, is filled with them. These are called
the "endosperm cells," but differ from the endosperm cells of the
gymnosperms, in the fact that they are not developed until after
fertilization, and can hardly, therefore, be regarded as
representing the prothallium of the gymnosperms and