Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/249

237 PROPAGATION.] HORTICULTURE 237 are, however, sometimes so small that the tongue of the graft is dispensed with, and the two stems simply pared .smooth and bound together. In this way hardy rhododendrons of choice sorts, green house azaleas, the varieties of the orange family, camellias, roses, rare conifers, and numerous other plants are increased. In small subjects soft cotton is used for tying instead of bast, and grafting- wax is substituted for grafting-clay. The best is the French cold mastic &quot; L Homme Lefort.&quot; All grafting of this kind is done in the propagating house, at any season when grafts are obtainable in a fit state, the plants when operated on being placed in close frames warmed to a suitable temperature. Root- grafting is sometimes resorted to where extensive increase is an object, or where stem-grafting or other means of propagation are n t available. In this case the scion is grafted directly on to a portion of the root of some appropriate stock, both graft and stock being usually very small ; the grafted root is then potted so as to cover the point of junction with the soil, and is plunged in the bed of the propagating house, where it gets the slight stimulus of a gentle bottom heat. Dahlias (fig, 57) and rjseonies may be grafted Fid. 57. Root-Grafting of Dahlia. FIG. 58. Root-Grafting of Woody Plant. by inserting young shoots into the neck of one of the fleshy roots of each kind respectively the best method of doing so being to cut a triangular section near the upper end of the root, just large enough to admit the young shoot when slightly pared away on two sides to give it a similar form. In the case of large woody plants thus worked (fig. 58) the grafted roots, after the operation is completed, are planted in nursery beds, so that the upper buds only are exposed to the atmosphere, as shown at c in the figure. (11) By Buds. Budding is the inserting of a bad cut with a portion of bark of the plant to be propagated into the bark of the stock, where it is bound gently but firmly. Stone fruits, such as peaches, apricots, plums, cherries, &c., are propagated in this way, as well as roses, and many other plants. In the propagating house budding may be done at any season when the sap is in motion ; but for fruit trees, roses, &c. , in the open air, it is usually done in July or August, when the buds destined for the following year are completely formed in the axils of the leaves, and when the bark separates freely from the wood it covers. Those buds are to be preferred, as being best ripened, which occur on the middle portion of a young shoot. The simplest and most generally practised form of budding is that called Shield -budding or T-budding (fig. 59). The operator should be provided with a budding-knife in which the cutting edge of the blade is rounded off at the point, and which has a thin ivory or bone handle, for raising the bark of the stock. A horizontal incision is made in the bark quite down to the wood, and from this a perpendicular slit is drawn downwards to the extent of perhaps an inch, so that the slit has a resemblance to the letter T, as at n. A bud is then cut by a clean incision from the tree intended to be propagated, having a portion of the wood attached to it, and so that the whole may be an inch and a half long, as at d. The bit of wood r. must be gently withdrawn, care being taken that the bud adheres wholly to the bark or shield, as it is called, of which/ is a side view. The bark on each side of the perpendicular slit being then cautiously opened, as at b, with the handle of the knife, the bud and shield are inserted as shown at c. The upper tip of the shield is cut oil hori zontally, and brought to fit the oark of the stock at the transverse incision. Slight ties, of soft cotton wool or worsted, or even moist bast-matting, are then applied. In about a month or six weeks the ligatures may be taken away, when, if the operation has been , FIG. 59. Shield-Budding. successful, the bud will be fresh and full, and the shield firmly united to the wood. In the following spring a strong shoot will be thrown out, and to this the stock is headed down by gradations during the course of the summer. To be successful the operation should be performed with a quick and light hand, so that no part of the delicate tissues be injured, as would happen if they were left for a time exposed, or if the bud were forced in like a wedge. The union is effected as in grafting, by means of the organizable sap or cambium, and the less this is disturbed until the inner bark of the shield is pressed and fixed against it the better. Inverted T-budding, in which the two inci sions are in the form J_, is for some reasons preferable to the more ordinary method. (12) By Branch Cuttings. Propagation by cuttings is the mode Brand of increase most commonly adopted, next to that by seed^. It is cuttinj effected by taking a portion from a branch or shoot of the plant, and placing it in the soil. There are great differences to be observed in the selection and treatment of cuttings. Sometimes soft green shoots, as in Verbena (fig. 60, a], are used; sometimes the shoots must be half-ripened, and sometimes fully matured. So of the mode of preparation ; some will root if cut off or broken off at any point and thrust into wet earth or sand in a warm place (fig. 60, a) ; others require to be cut with the utmost care just below a joint or leaf-base, and by a keen blade so as to sever the tissues without tearing or bruising ; and others again after being cut across require to be split up for a short distance. It is usual and in most cases necessary to cut away the lower portion of a cutting up to just below the FIG. 60. Propagation by Cuttings. noae or joint (fig. 60, b, d, e). The intcrnodal parts will not often divide so as to form separate individual plants ; sometimes, however, this happens ; it is said that the smallest piece of Torenia asiatica, for instance, will grow. Then as to position, certain cuttings grow readily enough if planted outdoors in the open soil, some preferring shade, others sunshine, while less hardy subjects must be covered with a bell-glass, or must be in a close atmosphere with bottom heat, or must have the aid of pure silver sand to facilitate their rooting (fig. 60, c). Cuttings should in all cases be taken from healthy plants, and from shoots of a moderate degree of vigour. It is also important to select leafy growths, and not such as will at once run up to flower. Young shoots which have become moderately firm generally make the best cuttings, but sometimes the very softest shoots strike more readily. For all plants in a growing state spring is the safest time for taking cuttings. Cuttings of deciduous plants should be taken off after the fall of