284 PROPAGATION BY GRAFTING, ETC. 



grafted on the laburnum, as do the different varieties of Pyrus Avbma, when 

 grafted on the common thorn ; the common lilac attains a large size when 

 grafted on the ash ; and Tecoma radicans, when grafted on the Catalpa, 

 forms a round head with pendent branches, which are almost without ten- 

 drils. The hardiness of some species is also increased by grafting them, as 

 in the case of the Eriobotrya japdnica on the common thorn, and the Pis- 

 tacia vera on the P. Terebinthus ; the Quercus virens is rendered hardier 

 by being grafted on the evergreen oak ; but in other cases, the species are 

 rendered more tender, as when the lilac is grafted on the phillyrea. Those 

 species that are rendered hardier by grafting have probably tender roots, 

 and by being placed on such as are hardier, they suffer only from the cold 

 at top, instead of being injured by the effects of cold both at root and top ; 

 or if they grow more stunted, they will also be less susceptible of cold. The 

 period of flowering is well known to be accelerated by grafting ; and hence, 

 both in the case of fruit-trees and ornamental trees and shrubs, the shoots 

 of seedlings are frequently grafted on the extremities of the branches of old 

 trees ; in consequence of which, they blossom several years sooner than if 

 left on their own roots. The mountain ash, and the different varieties of 

 Pyrus Jf ria, produce double the number of fruits when grafted, to what 

 they do on their own roots. The increase of the size of fruits, more espe- 

 cially of kernel fruits, is said by Thouin to be often from a fifth to a fourth 

 part, but the number and size of seeds produced is diminished. The flavour 

 as well as the size of fruit is said to be altered by the graft. Thus pears 

 are said to become gritty on quince or thorn stocks ; and the greengage plum 

 to vary in flavour, according to the kind of plum-stock on which it is grafted; 

 producing insipid fruit on some stocks, and fruit of the most delicious flavour 

 on others ; the cherry also when grafted on the Cerasus Mahdleb, on the 

 wild cherry, on the bird cherry, or on the common laurel, will produce fruit 

 very different in flavour on each. The duration of trees is greatly altered 

 in certain cases by the graft ; the apple on the paradise stock is generally 

 shorter lived than on the crab-stock ; while the Pavia, grafted on the horse- 

 chesnut, has its longevity increased. The period of leafing and flowering 

 is also occasionally changed by the graft, the general effect of which is to 

 produce a somewhat earlier vegetation ; because the graft, by arresting the 

 descent of the sap, produces in some measure the effect of ringing. Thus 

 far as to the influence of the stock upon the scion. 



644. The influence of the scion on the stock is very limited, and as far as 

 experience has hitherto gone, it consists only in communicating disease. The 

 only proof of this is the fact of the bud of a variegated common jasmine 

 having been inserted in a species without variegated leaves, and having 

 communicated its variegation to the entire plant, both above and below the 

 graft. This, De Candolle observes, is in accordance with the theory of 

 Moretti, that variegation, being a disease, can be propagated in a tree in 

 every direction. We are not aware, however, that there is any example 

 on record of a variegated holly having communicated its variegation to the 

 stock ; or in fact, of any other variegated plant having done so but the 

 jasmine, which, however, is a fact placed beyond doubt. 



645. The uses of grafting, in addition to those of all the other modes of 

 increasing plants by extension, are 



1. The propagation of varieties or species, which are not increased freely 

 by any other mode ; such as pears and other fruit-trees, oaks and other 

 forest-trees, and several species of Daphne and other shrubs. 



