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 colored_. 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.
[Illustration: FIG. 11.--PLANT OF A WILD SUNFLOWER.]
[Illustration: FIG. 12.--FRAMEWORK OF FIG. 11.]
=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.
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, golden rod,
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, bull nettle, and false indigo of
the Southern states.
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 are usually longer lived 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.
[Illustration: FIG. 14.--A TREE. The weeping birch.]
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._
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.