The characteristics of a potato, such as quality, productiveness, healthfulness, uniformity of size, etc., depend much on the nature of the soil on which it originated. These characteristics, some or all, imbibed by the minute potato from the ingredients of the soil, at its first growth from the seed of the potato-ball, adhere with great tenacity to it through all its generations. A seedling may, in size, color, and form resemble its parent; but its constitution and quality are in a great degree dependent on the nature of the soil, climatic influences, and other accidental causes. True crosses are generally more vigorous and healthy than others; and it is probably to accidental crosses we are indebted for many varieties that differ so widely from their parents. A cross is most apparent to the eye when the parents are of different colors, in which case the offspring will be striped or marked with the colors of each parent. 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.