THE PLANT BODY
=The Parts of a Plant.=—Our familiar plants are made up of several
distinct parts. The most prominent of these parts are _root, stem,
leaf, flower, fruit, and seed. Familiar plants differ wonderfully
in size and shape_,—from fragile mushrooms, delicate waterweeds and
pond-scums, to floating leaves, soft grasses, coarse weeds, tall
bushes, slender climbers, gigantic trees, and hanging moss.
=The Stem Part.=—In most plants there is a _main central part or
shaft_ on which the other or _secondary parts_ are borne. This main
part is the =plant axis=. Above ground, in most plants, the main
plant axis bears the _branches_, _leaves_, and _flowers_; below
ground, it bears the _roots_.
The rigid part of the plant, which persists over winter and which
is left after leaves and flowers are fallen, is the =framework= of
the plant. The framework is composed of both root and stem. When
the plant is dead, the framework remains for a time, but it slowly
decays. The dry winter stems of weeds are the framework, or skeleton
of the plant (Figs. 11 and 12). The framework of trees is the most
conspicuous part of the plant.
=The Root Part.=—The root bears the stem at its apex, but otherwise
it normally _bears only root-branches_. The stem, however, _bears
leaves, flowers, and fruits_. Those living surfaces of the plant
which are most exposed to light are _green or highly coloured_. The
root tends to grow _downward_, but the stem tends to grow _upward
toward light and air_. The plant is anchored or fixed in the soil by
the roots. Plants have been called “earth parasites.”
=The Foliage Part.=—The _leaves precede the flowers_ in point of
time or life of the plant. _The flowers always precede the fruits
and seeds._ Many plants die when the seeds have matured. The whole
mass of leaves of any plant or any branch is known as its _foliage._
In some cases, as in crocuses, the flowers seem to precede the
leaves; but the leaves that made the food for these flowers grew the
preceding year.
=The Plant Generation.=—The course of a plant’s life, with all the
events through which the plant naturally passes, is known as the
plant’s =life-history=. The life-history embraces various stages,
or epochs, as _dormant seed_, _germination_, _growth_, _flowering_,
_fruiting_. Some plants run their course in a few weeks or months,
and some live for centuries.
[Illustration: FIG. 11.—PLANT OF A WILD SUNFLOWER.]
[Illustration: FIG. 12.—FRAMEWORK OF FIG. 11.]
The entire life period of a plant is called a =generation=. It is the
whole period from birth to normal death, without reference to the
various stages or events through which it passes.
A generation begins with _the young seed_, not with germination. _It
ends with death_—that is, when no life is left in any part of the
plant, and only the seed or spore remains to perpetuate the kind. In
a bulbous plant, as a lily or an onion, the generation does not end
until the bulb dies, even though the top is dead.
When the generation is of only one season’s duration, the plant is
said to be =annual=. When it is of two seasons, it is =biennial=.
Biennials usually bloom the second year. When of three or more
seasons, the plant is =perennial=. Examples of annuals are pigweed,
bean, pea, garden sunflower; of biennials, evening primrose, mullein,
teasel; of perennials, dock, most meadow grasses, cat-tail, and all
shrubs and trees.
=Duration of the Plant Body.=—Plant structures which are more or
less soft and which die at the close of the season are said to be
=herbaceous=, in contradistinction to being =ligneous= or =woody=.
A plant which is herbaceous to the ground is called an =herb=; but
an herb may have a woody or perennial root, in which case it is
called an =herbaceous perennial=. Annual plants are classed as herbs.
Examples of herbaceous perennials are buttercups, bleeding heart,
violet, water-lily, Bermuda grass, horse-radish, dock, dandelion,
goldenrod, asparagus, rhubarb, many wild sunflowers (Figs. 11, 12).
Many herbaceous perennials have _short generations_. They become weak
with one or two seasons of flowering and gradually die out. Thus,
red clover usually begins to fail after the second year. Gardeners
know that the best bloom of hollyhock, larkspur, pink, and many other
plants, is secured when the plants are only two or three years old.
Herbaceous perennials which die away each season to bulbs or tubers,
are sometimes called =pseud-annuals= (that is, _false annuals_). Of
such are lily, crocus, onion, potato, and bull nettle.
True annuals reach old age the first year. Plants which are normally
perennial _may become annual in a shorter-season climate by being
killed by frost_, rather than by dying naturally at the end of a
season of growth. They are climatic annuals. Such plants are called
=plur-annuals= in the short-season region. Many tropical perennials
are plur-annuals when grown in the north, but they are treated as
true annuals because they ripen sufficient of their crop the same
season in which the seeds are sown to make them worth cultivating, as
tomato, red pepper, castor bean, cotton. Name several vegetables that
are planted in gardens with the expectation that they will bear till
frost comes.
[Illustration: FIG. 13.—A SHRUB OR BUSH. Dogwood osier.]
Woody or ligneous plants usually live longer than herbs. Those that
remain low and produce several or many similar shoots from the base
are called =shrubs=, as lilac, rose, elder, osier (Fig. 13). Low and
thick shrubs are =bushes=. Plants that produce one main trunk and
a more or less elevated head are =trees= (Fig. 14). All shrubs and
trees are perennial.
Every plant makes an effort _to propagate, or to perpetuate its
kind_; and, as far as we can see, this is the end for which the plant
itself lives. _The seed or spore is the final product of the plant._
[Illustration: FIG. 14.—A TREE. The weeping birch.]
SUGGESTIONS.—=8.= The teacher may assign each pupil to one plant in
the school yard, or field, or in a pot, and ask him to bring out
the points in the lesson. =9.= The teacher may put on the board
the names of many common plants and ask the pupils to classify
into annuals, pseud-annuals, plur-annuals (or climatic annuals),
biennials, perennials, herbaceous perennials, ligneous perennials,
herbs, bushes, trees. Every plant grown on the farm should be so
classified: wheat, oats, corn, buckwheat, timothy, strawberry,
raspberry, currant, tobacco, alfalfa, flax, crimson clover, hops,
cowpea, field bean, sweet potato, peanut, radish, sugar-cane,
barley, cabbage, and others. Name all the kinds of trees you know.