282 



PROPAGATION BY GRAFTING, ETC. 



640. The conditions essential to the success of the graft are the exact 

 coincidence of the alburnum and the inner bark of the scion with those of 

 the stock. The graft is effected in two forms : that of a cutting or scion, 

 which consists of wood and bark with buds (as in grafting and inarcliing), 

 and that of a bud, which consists of a shield of bark, containing a bud or 

 buds, but deprived of its wood, as in budding. In the case of the scion it is 

 essential to success that its alburnum coincide exactly with that of the 

 stock ; and in the case of the bud it is essential that the disk of bark to which 

 it is attached should be intimately joined to the alburnum of the stock by 

 being placed over it, and gently pressed against it by means of ligatures. 

 The buds of the scion and of the shield are supplied with sap from the 

 alburnum of the stock, and develop themselves in consequence. As a proof 

 that it is the ascending sap which supplies the nourishment in both cases, 

 the scion and the bud succeed best when the stock is cut over almost 

 immediately above the graft ; and when the scion or the shield are placed 

 immediately over a part of the stock which contained buds. The success 

 of a scion or a bud placed in the internodia of the stock where no normal 

 buds can exist, will therefore be much less certain than if it were placed on 

 the nodia ; because the vessels which conducted the descending sap to the 

 original buds are ready to supply it to those which have taken their place. 

 Hence in the case of the graft, fig. 194, the stock is cut sloping, and so as 

 to have a bud on or near the upper extremity of it, in order to prevent the 

 stock from dying down behind the graft ; and the section a, against which 

 the scion is to be placed, is made at the lower part of the sloping section, in 

 order to insure abundance of sap at its upper extremity as well as at its 

 lower; for were there no bud to expend the sap, it would cease to be 

 impelled through that part of the stock, which would consequently die. 

 By the end of August the scion and stock will be united, and the section at 

 the top of the latter healed over perhaps as far as c / and if the heel, or part 

 above c, is then cut off, the stock will probably be completely healed over 

 by the end of the season. 



641. Anatomical analogy. Plants can only be budded or grafted on one 

 another within certain limits, and these depend on the anatomy or organic 

 structure of the tissue, and the physiology or vital functions of the organs of 

 the plant ; but the anatomy of the cellules and the structure of the vessels 

 are so delicate and difficult to observe, that the differences between plants in 

 these respects are not sufficient to enable ns to amve at any practical con- 

 clusion from examining their organisation, and hence our only guide in this 

 matter hitherto has been experience. From this it is found that as plants 

 of the same natural family have an analogous organisation, they alone can 

 be grafted on one another with any prospect of success ; though the success 

 of the operation even within this limit will not always be complete ; partly, 

 perhaps, from some difference in organic structure, as in the case of the 

 apple and pear, which can only be united for a few years, but chiefly on 

 account of the physiological differences which may and do frequently exist. 

 Hence it follows that the greater part of what is recorded by the ancients, 

 respecting the grafting of plants of one family on those of another totally 

 opposite, such as the jessamine on the orange, the vine on the walnut, &c., 

 is without foundation in fact. The mistletoe is the only exception to the 

 general laws of grafting, as it seems to grow equally well on plants of many 

 different families, and this is accounted for from the mistletoe only attracting 



