238 



THE GARDENER'S ASSISTANT. 



from them; but the stock does not otherwise 

 essentially alter the nature of the tree grafted 

 upon it. There is a common communication of 

 fluids between the vessels formed above and 

 below the line a b, but the Pear and Quince form 

 their own peculiar secretions from the same 

 common source. Wherever there is Quince bark 

 in a healthy state, under it Quince wood alone 

 will be formed; and wherever there is Pear bark, 

 Pear wood only will be produced. The elabor- 

 ated sap from leaves on shoots pushed by the 

 buds g h does not in its descent form a layer of 

 Pear wood from b to k over the Quince, although 

 M. Gaudichaud and others were of opinion that 

 wood was an assemblage of the roots of buds, 

 extending from the latter to the extremities of 

 the roots. 



" A graft bears the same relation to its stock 

 as an adventitious shoot to the plant on which 

 it grows. When the parts have once united by 

 means of the cellular tissue, and when the first 

 fibro-vascular elements have been formed, there 

 is perfect continuity between the wood and the 

 cambium, or between the inner bark of the stock 

 and those of the graft. All the other anatomical 

 phenomena are also the same, for although the 

 nature of the stock is not modified by the graft, 

 the vascular filaments (called erroneously radical 

 fibres) or vessels, for they are nothing else, do 

 not the less appear to descend from the graft 

 to the stock, in the same way as they seem to 

 descend from the adventitious shoot to the stem 

 that bears it. This is in both cases merely an 

 appearance, because cellular multiplication is 

 always carried on horizontally, and because it 

 is the cellules which result from this horizontal 

 multiplication which change, some into vessels 

 and others into woody fibres and medullary rays. 



"Like the adventitious shoot, the graft draws 

 nutriment from the wood of the stock, it elabo- 

 rates it in its leaves, and returns it principally 

 by its inner bark to the lower part of the plant. 

 In descending from cell to cell the juices leave 

 part of their assimilable substance ; each cellule 

 appropriates what is best adapted to its nature. 

 This is the reason why the nature of the stock is 

 no more modified by the juices which descend 

 from the graft than the latter is by the juices 

 which it derives from the stock. The cells nour- 

 ished in this manner produce, by their division 

 in a horizontal direction, cells of the same nature 

 as themselves, which are modified according to 

 the functions they are called on to fulfil." 

 (Tread.) 



Affinity between Graft and Stock.— However 

 well the operation of grafting may be performed, 



and that in accordance with the principles already 

 explained, yet the results will be unsuccessful 

 unless the stock and scion are nearly related, 

 such as varieties of the same species, species of 

 the same genus, or genera of the same natural 

 order, beyond which the power does not extend. 

 The Pear will succeed on the Pear, Quince, Haw- 

 thorn, Mountain-Ash, and Medlar; but it can 

 scarcely be said to do so on the Apple, although 

 it is less dissimilar in appearance than some of 

 those above mentioned, and which have, in fact, 

 a greater generic difference. The Peach and 

 Nectarine succeed on the Almond, a species of 

 the same genus, and also on the Plum, a different 

 genus. Much as is practically known with regard 

 to the species and varieties that will agree with 

 each other when grafted, yet there is much which 

 can only be learned by experience. For instance, 

 some kinds of Pears do not succeed well on the 

 Quince ; and it is only after trial that such as do, 

 and such as do not, can be distinguished. 



Modifying Influence of the Stock upon the Graft. 

 — This chiefly arises from the stock supplying 

 the graft with a greater or a less amount of nour- 

 ishment than it would receive from its natural 

 root, and consequently producing a more or less 

 vigorous growth. It is, however, to be remarked, 

 that if a weak-growing variety is worked on a 

 stock that is comparatively too vigorous, a strong 

 growth may be induced in the first instance ; but 

 in such cases a disparity in the rate of increase 

 in the size of the stems checks the free circulation 

 of the sap at the point of junction, and the tree 

 is apt ultimately to become stunted. In short, 

 too great a disparity in the nature of the graft 

 and stock should be avoided, if a steady growth 

 be considered desirable. When the nature of the 

 stock is such that its stem increases in diameter 

 quicker than that of the scion, the latter usually 

 grows more vigorously than on its own root; but 

 as the swelling increases at the junction beyond 

 certain limits, the flow of sap is checked, and a 

 degree of vigour annually decreasing is the con- 

 sequence. When, on the contrary, the stem of 

 the stock is naturally of slower growth than that 

 of the kind worked upon it, a dwarfing effect is 

 the immediate result. Such, for instance, is the 

 case when a variety of the Apple is worked on 

 the French Paradise. 



The hardiness of the stock is of great import- 

 ance in the cultivation of trees and shrubs indi- 

 genous to southern climates, for many of such 

 plants either perish or thrive badly on their own 

 roots when planted in the comparatively cold soil 

 of Britain. They are, of course, affected some- 

 what injuriously by the coldness of our atmo- 



