The Seckel and Louise Bonne de Jersey Pears, for instance, which it is proposed to cross, possess to begin with, many desirable qualities. They are both hardy, adapted to the climate, good bearers, and yield fruit of first rate excellence. But the fruit of Louise Bonne de Jersey is larger and handsomer than that of the Seckel; while the fruit of the Seckel is superior in quality to that of the Louise Bonne. If, therefore, seeds of Louise Bonne were fertilised by the Seckel, and the fruit, bearing these seeds, made by superior management to attain a greater size and higher flavor, than by ordinary culture they ever attain to, it is likely a variety would be raised whose fruit would rival the Seckel in quality, and Louise Bonne in size and beauty. I need not pursue this further; it must be sufficiently apparent that cross-breeding when properly conducted, is a short cut to perfection - it enables one to effect in a few generations, what the former practice would have taken many generations to accomplish; hence, the truly marvellous improvement which has been made within the last twenty years, in plants whose seedlings require a comparatively short period to arrive at maturity, as the rose, pelargonium, fuschia, calceolaria, strawberry, Ac.

Next, as to tho mode of cross-breeding plants. The apple, pear, peach, plum, cherry, raspberry and strawberry, all belong to the natural order Rosacea, and their flowers have an indefinite number of stamens, about twenty or more. But as one not previously acquainted with these organs, may be somewhat puzzled to distinguish them from the pistils, if the study is commenced with the flowers of these plants, it will be well to examine first some flowers which have a certain and fewer number of stamens. Take the currant, for example, one of the earliest plants in blossom, and found in almost every garden. With a pen-knife slit carefully down one side of a full bloom flower, so as to spread it open for examination. There will be found an outer covering, or envelope, divided at the edge into five small parts; this is the calyx of the flower; next are five small leaflets - the petals, situated alternately with the segments of the calyx; then we have five small bodies alternate with the petals, and seated like them, on the throat of the calyx; these are the stamens, or male organs, which produce the yellow fertilising dust, called pollen.

In the center of the flower is the pistil, or female organ, a small, greenish, thread-like point, more or less two-cleft at the summit, and which is seated directly on the miniature berry containing the embryo seeds, and not on the calyx, as the stamens. Having well examined these flowers, there will be no difficulty in distinguishing similar parts in the flowers of other plants. In the pear, there is the green calyx outside, divided at the edge into fire small segments; then there are five large distinct petals, next numerous stamens, each tipped with a little head or anther, producing the yellow pollen grains; and lastly two to small pointed scissors, taking great care to leave the pilstil in the center of the flower uninjured; then, when these flowers have expanded, perfect flowers of the variety intended for the male parent, must he collected, and the pollen from them gently dusted on the summit of the pistil. The best time to apply [with a small camel's-hair brush] the pollen, is in the middle of a dry sunny day, and for fear of failure it should be repeated three or four days in succession.

The petals of the flowers have been observed to fall soon after the seeds were fertilised, and to retain their freshness for days longer, when this had not taken place.

Owing to the difference in the size of flowers, and the position of the stamens, the pear will be found much easier for the learner to operate on, than the currant.

There are one or two other points, which, if attended to, may contribute to the success of the experimenter. Not only should much care be bestowed in selecting varieties to raise seeds from, but they should be so managed as to ensure a healthy and vigorous growth, and the finest fruit and most perfect seeds which the variety cultivated is capable of producing. These objects may be attained by superior general culture, and by special expedients. Perhaps I may best explain how, by stating the plan I intend to follow in endeavoring to improve our native Black Currant of this region, Ribes floridum; it appears to me a much finer species to begin with than the JR. nigrum of Europe, the origin of the garden varieties: it has a neat habit of growth, bears abundant crops of tolerably well flavored fruit, and its blossoms are somewhat showy. My aim is to obtain a variety with flowers approaching the color of those of the Missouri Currant, R, aureum, and with fruit equal or superior in size and quality to that of the Black Naples. In raising plants or animals to be grown for profit, utility should never be sacrificed to mere show, but if we can combine the beautiful with the useful, it is well.

From several plants raised in the last year, I shall select three which have the cleanest and strongest branches, and whose roots are well developed from the base of the cuttings. This I have found a matter of some importance; why it is so, I shall endeavor to explain in another letter on the Season for Transplanting. The next consideration is, where and how the trees should be planted so that the organs of vegetation may perform their functions in the most efficient manner. A soil moderately rich, and free from stagnant water, should be selected, and a hole dug for each plant about six inches deep, and wide enough to admit the roots being laid out their full length; the small lateral fibres, as well as the main roots, should be spread, as the greater the space covered, the greater will be the means of the plant for obtaining food from the soil. It may be well to cover the roots slightly with earth, as contact with manure sometimes produces canker. The hole may then be filled up with a compost formed of decayed turf, well rotted stable manure, and charcoal, this being calculated to produce a steady and vigorous, but not over luxuriant growth. Abundance of food will avail but little if the plant has not the means of digesting it.