metimes with the two most
essential parts, i. e. stem and leaf, plainly discernible; sometimes
with no obvious distinction of organs until germination begins. This
incipient plant is called an EMBRYO.

9. In this section the Flax-plant is taken as a specimen, or type, and
the development and history of common plants in general is illustrated
by it. In flax-seed the embryo nearly fills the coats, but not quite.
There is a small deposit of nourishment between the seed-coat and the
embryo: this may for the present be left out of the account. This embryo
consists of a pair of leaves, pressed together face to face, and
attached to an extremely short stem. (Fig. 2-4.) In this rudimentary
condition the real nature of the parts is not at once apparent; but when
the seed grows they promptly reveal their character,--as the
accompanying figures (Fig. 5-7) show.

[Illustration: Fig. 1. Pod of Flax. 2. Section lengthwise, showing two
of the seeds; one whole, the other cut half away, bringing contained
embryo into view. 3. Similar section of a flax-seed more magnified and
divided flatwise; turned round, so that the stem-end (caulicle) of the
embryo is below: the whole broad upper part is the inner face of one of
the cotyledons; the minute nick at its base is the plumule. 4. Similar
section through a seed turned edgewise, showing the thickness of the
cotyledons, and the minute plumule between them, i. e. the minute bud on
the upper end of the caulicle.]

10. Before the nature of these parts in the seed was altogether
understood, technical names were given to them, which are still in use.
These initial leaves were named COTYLEDONS. The initial stem on which
they stand was called the RADICLE. That was because it gives rise to the
first root; but, as it is really the beginning of the stem, and because
it is the stem that produces the root and not the root that produces the
stem, it is better to name it the CAULICLE. Recently it has been named
_Hypocotyle_; which signifies something below the cotyledons, without
pronouncing what its nature is.

[Illustration: Fig. 5. Early Flax seedling; stem (caulicle), root at
lower end, expanded seed-leaves (cotyledons) at the other: minute bud
(plumule) between these. 6. Same later; the bud developed into second
pair of leaves, with hardly any stem-part below them; then into a third
pair of leaves, raised on a short joint of stem; and a fifth leaf also
showing. 7. Same still older, with more leave