eight every week of
its early growth, and may in time produce a huge amount of vegetable
matter, it is still to be asked what this vegetable matter is, where it
came from, and by what means plants are able to increase and accumulate
it, and build it up into the fabric of herbs and shrubs and lofty trees.

396. =Protoplasm.= All this fabric was built up under life, but only a
small portion of it is at any one time alive. As growth proceeds, life
is passed on from the old to the new parts, much as it has passed on
from parent to offspring, from generation to generation in unbroken
continuity. _Protoplasm_ is the common name of that plant-stuff in which
life essentially resides. All growth depends upon it; for it has the
peculiar power of growing and multiplying and building up a living
structure,--the animal no less than the vegetable structure, for it is
essentially the same in both. Indeed, all the animal protoplasm comes
primarily from the vegetable, which has the prerogative of producing it;
and the protoplasm of plants furnishes all that portion of the food of
animals which forms their flesh and living fabric.

397. The very simplest plants (if such may specifically be called plants
rather than animals, or one may say, the simplest living things) are
mere particles, or pellets, or threads, or even indefinite masses of
protoplasm of vague form, which possess powers of motion or of changing
their shape, of imbibing water, air, and even other matters, and of
assimilating these into plant-stuff for their own growth and
multiplication. Their growth is increase in substance by incorporation
of that which they take in and assimilate. Their multiplication is by
spontaneous division of their substance or body into two or more, each
capable of continuing the process.

398. The embryo of a phanerogamous plant at its beginning (344) is
essentially such a globule of protoplasm, which soon constricts itself
into two and more such globules, which hold together inseparably in a
row; then the last of the row divides without separation in the two
other planes, to form a compound mass, each grain or globule of which
goes on to double itself as it grows; and the definite shaping of this
still increasing mass builds up the embryo into its form.

[Illustration: Fig. 433-436. Figures to illustrate the earlier stages in
the formation of an embryo; a single mass of protoplasm (Fig. 433)
dividing into two, three, and then into more incipie