Gardening Articles

How To Cross Varieties

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.

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