"There are as many ways of grafting as there are of whit tling," a wise horticulturist has remarked. The object in each case is to fit the cion (or bud) to the stock with the cambium of the two in close contact. A tied band of raffia or a covering of grafting wax, or both, excludes the air and injurious substances and holds the parts securely.
Cleft grafting is very common, in changing the variety of a 'mit tree. For other methods see Bailey's "Nursery Book," or any other horticulturist's guide. Cleft grafting is typical. The end of a branch is sawed squarely off. It should be less than two inches in diameter. A special grafting knife is used next. Its blade, set across the stub, is driven in by the stroke of a mallet. A tooth on the end of the knife is inserted in the split thus made, to hold the cleft open. A cion is inserted at each end of the split, so that there may be two chances for it to "stick" fast and grow, instead of one. Each don is a bit of a twig, bearing two or three buds, and sharpened by two slanting cuts to fit the cleft stub. When set, there should be a bud on a level with the top of the stub. It should be held tight between the lips of the cleft, by the "spring" of the two sides (the tooth being removed now), and the green cambium of cion and stock should pinch. Now grafting wax is moulded about the graft and the work is complete.
The best time to graft is just before the buds swell in the spring. If all is well, leaves will shoot upon the cions as April comes on; if one fails, no matter. By grafting one-third of the limbs each year for three years the whole treetop can be changed from one variety to another. Several varieties may be grafted on one tree.
Budding is usually done in summer or early fall. Shield budding is the common nursery method. A T-shaped cut through the bark of the slender whip is made on the north side just above the ground. A twist of the knife loosens the four corners of the bark. An oval bit of bark with a bud in its centre is cut from a twig of the desired variety; a leaf stem serves as a convenient handle. The disc of bark bearing the bud is slipped down under the thin flaps of bark on the stock. They hold the bud in place against the cambium of the stock. A wrapping of raffia protects and binds the wound. It is cut as soon as the bud "sticks," or it would impede the growth. The stem above is cut off, so that the treetop formed later may be the outgrowth of this bud. Budding is usually done upon seedlings of one season's growth, and is ordinarily intrusted to an expert, with a helper to tie the buds he sets. A record of three thousand buds a day is not un usual.
Weeping forms are propagated by grafting cions from weep ing trees upon erect stocks. The popular notion that they are produced by inserting the buds upside down is entirely false. Horticultural varieties are all grafted, e. g., cut-leaved, variegated, pyramidal and double-flowered varieties of standard species. These peculiarities are originally discovered as seedling varia tions in the nursery rows or "freak" branches on normal trees. A good character is hoarded, emphasised and multiplied; then exploited as a new variety. It would not come true from seed, even if it appeared first in a seedling. It is too new to be fixed, except by grafting cions from the original tree.
The extent to which grafting and budding can be practised was at first much exaggerated. Virgil prophesied thus: "Thou shalt lend Grafts of rude arbute unto the walnut tree: Shalt bid the unfruitful plane sound apples bear, Chestnuts the beech, the ash blow white with the pear, And under the elm, the sow on acorns fare." Pliny's report of "cherry growing upon the willow, the plane upon the laurel, the laurel upon the cherry, and fruits of various tints and hues all springing from the same tree at once," is like other of his vain imaginings.
Abram Cowley, in 1666, comes nearer the truth, as he should with centuries of experience to lean upon, in these lines: "We nowhere Art do so triumphant see, As when it Grafts or Buds the Tree; • He bids the ill-natur'd Crab produce The gentle Apple's Winy Juice He does the savage Hawthorn teach To bear the Medlar and the Pear He bids the rustic Plum to rear A noble Trunk and be a Peach." The modem rule of "seed on seed and pit on pit' is embodied in this account. The species named are all in the same botanical family at least. Plums are budded upon peach stocks in the South. Peach-rooted trees thrive better in the hot, sandy soil than plum-rooted trees do. In the Northern States peaches are budded on plum stocks which are hardier in the native kinds. Crab apples, native to various regions, prove good stocks for introduced varieties of apples.
The limits of grafting are not very well defined yet. The safest and most practicable method is to inter-graft varieties of one species. Remoter relationships admit of union sometimes, as the peach and plum, which are of different species; by some authorities these are considered of different genera. The moun tain ash has served as a stock for apples—again, two different genera. But these instances are plainly beyond safe limits.
The origination of new varieties by hybridisation is an entirely different subject. Its variations come through the seeds. Here the pollen, scattered in various ways when plants blossom, falls on the pistils of flowers somewhat indiscriminately. Especially is this true of wind-fertilised flowers which produce pollen in abundance and of a dry, powdery sort. The pollen lies inert on the stigmas of alien species. It fertilises those of its own kind. There are intermediate varietal relationships and very closely related species in certain families. In these cases natural crosses occur, flowers being fertilised by pollen of another species. Seeds thus set produce hybrid plants, new kinds having characters of their two parents. Thus the species of willows are hopelessly intermixed. Natural crosses between oaks are frequently dis cernible in the woods. The white oak crosses with several species in its own (annual) group. The biennial or black oaks also intercross among themselves. But black and white oaks do not cross.
Artificial crosses are frequently made by plant breeders for scientific and economic reasons. Some of the best horticultural varieties of fruits and flowers are artificial hybrids. Among these are the Kieffer pear, the wild goose plum, and various roses, grapes, begonias, cannas and pelargoniums. Hybrids are propa gated by division.