280 



PROPAGATION BY GRAFTING, ETC. 



some saxifrages, potentillas, &c. The joints of these plants rest natumlly 

 on the ground, send down roots^, and upwards leaves or shoots ; and being 

 separated from the intemodi of the stolones, constitute rooted plants. 

 Very little assistance from art is required in this mode of propagation ; 

 but the soil may be loosened and enriched, and the joint pressed firmly 

 against the soil, by pegging it down with a hooked peg, or by laying a small 

 stone on each side of the joint. The principal plant propagated in this 

 manner in gardens is the strawberry. 



636. Simple division is an obvious mode of propagating all herbaceous 

 perennials, not bulb-bearing, and all shrubs which produce numerous suckers. 

 The most common mode is to take up the entire plant, and separate it into 

 as many stems as have roots attached ; or if only a few plants are wanted, 

 these may be taken off the sides of the plant without greatly disturbing the 

 interior of the root stock. 



§ VI. Propagation by grafting, inarching, and budding, 



637. The term graft is in England generally confined to one mode of 

 performing that operation, viz., grafting with detached scions ; but it is our 

 intention in this article to use it, in the continental sense, as a generic term, 

 including, also, inarching, or gi-afting with attached scions, and budding or 

 grafting by means of a bud attached to a plate of bark. The principle on 

 which all these operations are founded is the phenomenon of the union of 

 newly generated tissues when in the act of being generated. No union can 

 take place between the parts of plants previously formed, but only when 

 these parts are in the act of forming. Thus two shoots or branches may 

 be selected, and by means of similar sections be most accurately joined, and 

 placed under the most favourable circumstances for uniting, as in fig. 194, 

 representing a stock and a scion ; yet when 

 the two are bound together, though a union 

 ultimately does take place, not one particle of 

 the existing tissue at the time of grafting W- 

 becomes united with similar tissue brought in 

 contact with it. Close contact is all that takes 

 place with regard to these surfaces of the scion 

 and stock, for a vital union only occurs when 

 nascent tissues meet. The parts a, a, which 

 are alburnum of the preceding year, never 

 unite. The vital union is formed solely by the 

 coalition of newly generated tissues, thrown 

 out by such parts as have the power of gene- 

 rating them. This power does not exist in 

 the heart-wood, nor in the outer bark, but 

 only in the alburnum, or rather the substance 

 imbedded between it and the inner bark, con- 

 stituting the cambium, represented by the 

 lines, b, b. If the sections are placed against 

 each other, so as the inner barks coincide, the p. „ . 



' . . ' tig. l^i. Scton and slock to illustrate the 



Dcion may perhaps derive an immediate supply principle on which they are united. 

 of moisture ; but it does so only in a mechanical way, and a piece of dry 

 sponge might as tmly be said to have formed a connexion from its absorbing 

 moisture, in consequence of being placed on the top of a stock, as the scion 



