Hybridizing, Or Cross-Breeding, though not quite identical, have with the gardener similar objects, viz., either improving the beauty of his flowers, or the flavour and prolificacy of his fruits and culinary products.

Hybridizing, strictly speaking, is obtaining a progeny between two different species; and cross-breeding is obtaining a progeny between varieties of the same species. The progeny of hybrids cannot produce seed; but cross-breeds are fertile. My own observations, and those of others, justify the following statements, as affording some guide to the raiser of varieties: -

1. The seed-vessel is not altered in appearance by impregnation from another plant; therefore, no hasty conclusion of failure is justified by that want of change.

2. The colour of the future seed, not of that first hybridized, seems to be most influenced by the male plant, if its seeds and flowers are darker than those of the female. Mr. Knight found, that when the pollen of a coloured-blossomed pea was introduced into a white one, the whole of the future seeds were coloured. But when the pollen of a white blossom was introduced to the stigma of a coloured blossom, the whole of the future seeds were not white. Capt. Thurtell, from his experiments on the pelargonium, also informs me, that he has always found the colour and spot of the petals to be more influenced by the male than by the female parent. Indeed, all experience proves that the progeny usually, though not invariably, most resembles in colour the male parent.

3. Large stature and robustness are transmitted to the offspring by either parent. It does not absolutely matter for obtaining this characteristic, whether it be the male or female which is large; but Mr. Knight generally found the most robust female parent produced the finest offspring.

4. Capt. Thurtell, from lengthened observation and experiment, has ascertained that the form of the petals follows most closely that of the female parent.

5. Mr. Knight says that the largest seed from the finest fruit that has ripened earliest and most perfectly, should always be selected. In stone-fruit if two kernels are in one stone, these give birth to inferior plants.

6. The most successful mode of obtaining good and very distinct varieties, is to employ the pollen from a male in a flower grown on another plant than that bearing the female parent. To avoid previous and undesired impregnation, the anthers in the female parent, if they are produced in the same flower with the pistils, must be removed by a sharp-pointed pair of scissors, and the flower inclosed in a gauze bag, to exclude insects, until the desired pollen is ripe. Another effectual mode of avoiding undesired impregnation, is bringing the female parent into flower a little earlier than its congeners, and removing the anthers as above described: the stigma will remain a long time vigorous if un-impregnated.

7. Although the fertility of all the seed in one seed vessel may be secured by applying pollen only to one style, even where there are several, yet the quantity of pollen is by no means a matter of indifference. Koelreuter found, that from fifty to sixty globules of pollen were required to complete the impregnation of one flower of Hybiscus Syriacus; but in Mirabilis jalapa, and M. longiflora, two or three globules were enough; and in the case of pelargoniums, Capt. Thurtell says two or three globules are certainly sufficient.

8. M. Haquin, a distinguished horticulturist at Liege, has impregnated flowers of the Azalea with pollen kept six weeks; and Camellias with pollen kept sixty-five days. He gathers the stamens just previously to the anthers opening, wraps them in writing-paper, places them in a warm room for a day, collects the pollen they emit, and preserves it in sheet lead in a cool dry place. M. Godefroy suggests, that two concave glasses, like those employed for vaccine virus, would be better. The globules of the pollen must not be crushed. M. Haquin thinks the pollen of one year will be effective if preserved until the year following. Mr. Jackson, of Cross Lanes Nursery, near Bedale, says, he has found the pollen of the Rhododendron Smithii tigrinum retain its fertilizing power even for twelve months.

9. It is easy to discern whether impregnation has been effected, as in such case the stigmas soon wither. The stigmas which have not received the pollen remain for a long time green and vigorous. "By the aid of the Stanhope lens," observes Capt. Thurtell, in a letter now before me, "I fancy I can discover the seed of the pelargonium being closed over in the space of four hours after impregnation".

10. When double flowers are desired, if a double flower should chance to have a fertile anther or two, these should be employed for fertilization, as their offspring are almost sure to be very double.

11. Many analyses of the pollen of various plants have been made by chemists, without throwing any light upon hybridizing. M. Grotthus found the components of twenty-six grains of the pollen of the tulip were -

12. Supertoetation has been doubted; but as it occurs in the dog, we see no reason for disbelieving its possibility in plants. Capt. Thurtell thinks it may be done by the bee introducing mingled pollens at the same instant. Then why not if a similar mixture is inserted by the camel's-hair pencil of the cultivator?

13. Plants nearly related, that is, closely similar in the structure of their various parts, are those only which will immediately impregnate each other; but it is impossible, at present, to say what families of plants may or may not be brought into fertile union through intermediate crosses. A very short time ago, the azalea and rhododendron were thought incapable of such union; but this opinion is now exploded, for rhododendron ponticum has been fertilized with the pollen of azalea sinensis, and the progeny between that evergreen and this deciduous shrub, is the previously unknown phenomenon, a yellow rhododendron. Though such unions may be effected, I entirely agree with Mr. Knight in anticipating that the progeny will be mules, incapable of producing offspring.