In order to comprehend fully the principles of this subject, and their
application to practical operations, it will be necessary to take a
general view of the generative organs of the vegetable kingdom, and the
manner in which they act in the production of their species. If we
examine a perfect flower, we shall find that it consists essentially of
two sets of organs, one called the pistils, the other the stamens. The
pistils are located in the centre of the flower, and the stamens around
them. The summit of the pistil is called the stigma; and on the top of
each stamen is situated an anther--a small sack, which contains the
pollen, a dust-like substance, that fertilizes the ovules or young seeds
of the plant.
These organs are supposed to perform offices analogous to those of the
animal kingdom--the stamens representing the male, and the pistils the
female organs.
When the anthers, which contain the pollen, arrive at maturity, they
open and emit a multitude of minute grains of pollen; and these, falling
on the pistils of the flower, throw out hair-like tubes, which penetrate
through the vascular tissue of the pistil, and ultimately reach the
ovules, thus fertilizing them, and making them capable, when mature, of
reproducing plants of their own kind.
The ovules are the rudimentary seeds, situated in a case at the base of
the pistils, each consisting of a central portion, called the nucleus,
which is surrounded by two coats, the inner called the secundine, the
outer the primine. When the hairlike tube of the pollen-grain passes
through the orifice in the coatings of the ovule, and reaches the
nucleus, or embryo sack, it is supposed to emit a spermatic or plantlet
germ, which passes through the wall of the embryo sack and enters the
germinal vesicle contained in it. The vesicle corresponds to the
vesicle, or germinal spot, in the eggs of birds, and ovum of mammiferous
animals. The germ remains in the vesicle, and finally becomes the
embryo, fully developed into a plantlet, as may be seen in many seeds.
Flowers of plants are called perfect when the stamens and pistils are in
the same flower, as the apple; mon[oe]cious, when in different flowers
and on the same plant, as the white oak; and di[oe]cious, when in
different flowers and on different plants, as in the hemp. In that class
of plants in which the stamens, or males, are on one plant, and the
pistils, or females, on another, the males of course must always remain
barren; and the pistilates, to be fruitful, must have the pollen from
the anthers of the staminate brought in contact with its stigma by wind,
insects, or other means. In plants with perfect flower, the stamens are
generally situated around and above the pistil, so that the pollen falls
upon the stigma by mere force of gravity. In the potato, the pollen is
conveyed from the anthers to the stigma by actual contact of the two
organs.
Cross-breeding in plants consists in fertilizing one variety with the
pollen of another variety of the same species. The offspring is called a
cross-breed, or variety. The process of cross-breeding consists in
taking the pollen of one variety and applying it to the stigma of
another variety, in such a way as to effect its fertilization. This is
done by cutting away (with scissors) the stamens of the flower to be
fertilized, a short time before they arrive at maturity, and taking a
flower in which the pollen is ripe, dry, and powdery, from the stalk of
the variety wished for the male parent; and holding it in the right
hand, and then striking it on the finger of the left, held near the
flower, thus scattering the pollen on the stigma of the pistil of the
flower to be fertilized. The utmost care should be taken to apply the
pollen when the flower is in its greatest vigor, and the stigma is
covered with the necessary coating of mucus to insure a perfect
connection of the pollen with the pistil, and make the fertilization
perfect. All flowers not wanted in the experiment should be removed
before any pollen is formed.
It is necessary to tie a thin piece of gauze over the flower to be
fertilized, before and after crossing, to prevent insects from conveying
pollen to it, thus frustrating the labors of the operator. If the
operation has been successful, the pistil will soon begin to wither; if
not perfect, the pistil will continue fresh and full for some days.
This _modus operandi_ is substantially the same in crossing fruits,
flowers, and vegetables throughout the vegetable kingdom.
Hybridizing differs from cross-breeding only in fertilizing one species,
or one of its varieties, with the pollen of another species, or one of
its varieties, of the same or a different _genus_. The offspring is
called a hybrid, or mule. Hybrids, with very few exceptions, are
sterile, they fail to propagate themselves from seed, and must, to
preserve them, be propagated by grafts, layers, or suckers. No change is
perceptible in the fruit produced from blossoms upon which the operation
of cross-breeding or hybridizing has been performed; but the seed of
fruits so obtained may be planted with the certainty of producing a
fruit or tuber commingling the qualities, colors, and main
characteristics of both parents.
Experience, however, shows that the characteristics of the male
predominate somewhat in the offspring. To judicious cross-breeding and
hybridizing we owe most of our superior fruits and vegetables. If the
operation were more generally known and practiced by farmers, the most
gratifying results would be soon obtained, not only in the production of
the most valuable varieties of potatoes and other vegetables, but also
in fruits, flowers, and grain of every description.