GRAFTING is an art which has been practised from a period of remote antiquity; by whom it was discovered is unknown. The operation consists in placing two cut surfaces of one or of different plants under conditions which cause them to unite and grow together. The plant--usually termed the stock--on which the graft is inserted, should, in almost every case, be provided with roots, for the purpose of drawing and transmitting nutriment to support the graft after a union has taken place. The part inserted is called the scion, and is analogous to a cutting placed in the soil, although its growth is developed by nourishment supplied through the stock. The action of the one on the other is frequently marked and very important. Some fruit-trees, for instance, grow freely on one stock, but scarcely bear, whilst on others they produce abundant crops, though they do not grow so vigorously; nevertheless, although both are so intimately connected, they retain their individual characters distinct. The stock will become enlarged by the elaboration of sap in the leaves of the scion without the nature of the wood in either case being much altered, each part forming its own peculiar secretion from sap arising from the same source. Scions from variegated trees will frequently cause variegated shoots to develop on the stock far below the graft; and these can be used to increase the supply of a given form just as well as those produced by the original tree. The Golden Laburnum is a well-known case in point. The importance of the possibility of Grafting cannot be over-estimated, as, by its adoption, the propagation of varieties of fruits, flowers, many forest trees, shrubs, &c., is rendered available, and the good qualities or habits of any are retained, without alteration, excepting such modifications as may be caused by the superior constitution or special suitability of the stock. Grafting may also be employed for restoring defective branches on any part of an otherwise healthy fruit-tree, or for the insertion of fruit-bearing wood, where there is a deficiency. Seedling fruit-trees are brought more quickly into a bearing condition by being grafted on fruit-bearing stocks, so soon as sufficiently-matured scions can be obtained. The two sexes of monoecious plants may, in some cases, be brought together on one stock in order to eventually insure their reproduction by self-fertilisation. Certain conditions are essential for attaining success in Grafting. A great deal depends on the skill of the operator, the condition of the sap, a healthy growth in the stock and scion, and the season when the operation is performed. In order that a vital union may take place, it is essential that the two parts employed should have a natural affinity to each other, either as varieties of the same species, species of the same genus, or genera of the same natural order. In the works of celebrated ancient writers, accounts are given of various attempts having been made, and supposed unions effected, under conditions which have since been found impossible, on account of a natural affinity being non-existent. A temporary union has sometimes taken place, but not a vital and lasting one. A fundamental principle, which applies to every method of Grafting, is the necessity of forming a direct communication between the layers of inner bark in each of the parts to be united; as, without this, a perfect joining is not effected. The pithy or woody parts never unite, as may be frequently observed when grafted trees of long standing are cut down, and the ends of wood originally placed in contact are found to have become decayed. Provided this essential principle be kept in view, the methods of Grafting may be varied almost indefinitely. The natural vigour of the stock and scion should be somewhat similar for inducing a steady growth; but, at times, it is preferable that the scion should be the hardier and more vigorous of the two. This is exemplified, and the desired results attained, in many cases, by Grafting various strong-growing varieties of Apples on the Paradise stock, Cherries on the Mahaleb, and Pears on the Quince. In these and other instances, the stock is restricted in its root-growth, and the supply of sap transmitted to the grafted portion is, consequently, limited. This latter condition tends to encourage fruit-bearing instead of vigorous wood, and proves, by results, the modifying effect of the stock and the superior results in productiveness thereby secured. Double-grafting is sometimes adopted as another means for reaching the same end, by having a variety of intermediate growth inserted first on the stock, this to be ultimately grafted with the one it is intended to propagate. Fig. 133 is intended to illustrate what is here meant in the case of Grafting the Pear. The special influence exerted on the part of the stock or scion with certain varieties in either direction, can only be learned by experience. Grafting should be performed when the sap is in motion, between the time when it begins flowing in spring and a period before it ceases in autumn, avoiding the middle of summer, or any very hot weather. It is most largely practised, both indoors and outside, in early spring, the scions being slightly retarded by keeping them in a cooler place, or, in the case of fruit trees, previously cutting and inlaying them in the ground. Calm, moist weather is most suitable for the operation outside, which should always be skillfully performed, by means of clean cuts, a careful fitting of the parts together, and an exclusion of air by the application of grafting-clay or wax. Close frames or cool houses are requisite for tender plants, and for various evergreen trees or shrubs, until the parts have become united. Many of these do not require any clay or grafting wax, if kept moist, quite close, and shaded. Heat is unnecessary in the case of many hardy plants, a protection from the drying influence of wind and sun being all that is required. There are various methods of Grafting that may be successfully practised, according to the size or variety of subject it is intended to propagate or improve. The following are those most generally used, and all are subject to slight modifications under varied circumstances. In Fig. 134, A shows the mode of tying the graft adopted with many fruit trees, and B the work completed by the application of clay, which should be left in the shape shown, and be carefully fitted to the stock and scion. This plan may be employed either for dwarf or tall stocks. All grafts inserted outside should be protected, and kept from moving by a stake, which should reach nearly or quite to the top, and have both stock and scion secured to it, to prevent the latter becoming displaced.