Gardeners’ Chronicle, (Ser. 3) 21: 206-207 (Mar 27, 1897)
THE INFLUENCE OF THE GRAFT ON THE FRUIT
Scion

At whatever age in the history of horticulture the utility of the graft may first have become recognised, there is no doubt that a vast amount of information on the subject has gradually accumulated during an indefinitely long period of observation, and subsequently of methodical investigation. Extensive and important as the actual knowledge of the theory and art of grafting may be, there is also no doubt that much remains to be learnt, more particularly, perhaps, from a scientific standpoint. For although the most recent and authoritative works on horticulture indicate, for instance, nearly fifty different methods of grafting, the list is not infrequently extended by other new methods. Similarly, but to a much greater extent, is the knowledge increasing as regards the theory of grafting, the reason of course being that horticulturists were able to observe the apparent effects of the graft long before the physiology of plants was understood, even if considered. And even at the present day, not every man who can "graft" is in a position to investigate the effect of his work from a scientific point of view. To give the names of the men who have worked in this direction would be to mention many of the most eminent botanists of the century which is now at its close, and even a résumé of their interesting and useful results would extend much beyond the limits of a short article.

It is therefore now intended to refer to one aspect of the case only, viz., as regards the influence of the graft on the fruit of the Pear-tree, and in connection with a communication which has recently been made to the French Académie des Sciences, indicating the results obtained from observations made during three years by M. Gustave Rivière, the Director of the Versailles School of Horticulture, and M. G. Balhache.

On the general subject of grafting, it may be mentioned in parenthesis, and in the words of M. Charles Baltet, one at least of whose classical works on horticulture has been translated into the English language, that whilst unifying their existence the scion and the stock individually retain their original qualities, their characteristic properties, and each their proper constitution; their woody and cortical tissues continuing their development without any intermingling of their respective vessels or fibres. M. Baltet also employs a very graphic phrase, borrowed from the political world, which is, moreover, very applicable in this connection when he states that "grafting is a form of federative union wherein the interested parties retain their autonomy."

But whilst it is generally supposed and usually taught that the graft does not modify the specific character of the scion or of the stock, the above-mentioned explanation is not to  be regarded as an absolute law, as has been shown M. Daniel, whose researches on this subject have already been noticed in this journal (Gardeners' Chronicle, 1895, part i., p. 140). Daniel was enabled to show that an alteration of taste in the scion and in the stock was obtainable by means of the graft, the most marked instance being that of the Savoy Cabbage grafted on the Turnip, whereby the former acquired to a considerable extent the very characteristic taste of the latter plant. The phenomenon was, moreover, proved to be more than temporary and fortuitous, inasmuch as the seeds obtained from the scions so grafted reproduced plants bearing the same "abnormal" characteristics of taste, and thereby indicating a real commencement of hybridity.

This change of taste resulting from the graft, as demonstrated by Daniel, nevertheless referred to herbaceous plants only, and the phenomenon would be all the more important if it also obtained as regards fruit-trees and Vines. Happily, said Professor Gouiraud less than two years ago in the Revue de Viticulture, experience has hitherto shown that nothing similar occurs; and although, when the Phylloxera necessitated the reconstitution of many French vineyards by the American Vitis riparia, it was stated by many growers that the native Vines were losing their qualities and becoming "riparia-ised." For experiments conducted on an extensive scale afterwards indicated the supposition to be ill-founded, and that as excellent Grapes for the table are obtainable on the native as on the American stock. Similarly with fruit trees, says M. Gouiraud, Pears true to taste being obtained from grafts on the wild stock, with its bitter fruit; and the Sweet Almond may be grafted on the Bitter Almond without any modification of flavour. The same observer also stated that the only apparent effect of the graft, at any rate as regards the Vine, consists in a difference of vigour which is generally less marked, and of fructification, which is generally more abundant, consequent on the natural results of a greater or less affinity between the scion and the stock.

This opinion would not, however, appear to be applicable, without modification, to the fruit of the grafted Pear-tree, in consequence of the recently reported experiments of MM. Rivière and Bailhache, to which reference has already been made, and of which a full account is to be found in the Comptes Rendus (tome cxxiv., p. 477). These gentlemen state that it has been observed for a considerable period that fruit trees in general, and some varieties of Pear-trees in particular, undergo certain characteristic changes according to the nature of the stock on which the grafts are placed. And if the essential peculiarities of the varieties are not altered, certain notable modifications obtain as regards the vigour and early maturity of the trees, and the weight, colour, and taste of the fruit when the scion is grafted on Pear-stock, and when it is grafted on the Quince. No precise scientific investigations would, moreover, appear to have been previously made on this particular subject, and Rivière and Bailhache conducted their researches during three years on absolutely identical conditions in connection with a variety of Pear known as the Triomphe de Jodoigne. The two trees selected for experiment were of the same age, viz, fifteen years old, their growth had always been normal, they were trained on the same system, they grew side by side, and their roots were consequently nourished by the same soil. But one tree was grafted on the Pear stock, and the other on the Quince, and the following table shows certain variations in the nature of the fruit as indicated by analysis made in 1894, 1895, and 1896:--

Nature of Fruit On Pear Stock: Green
Grammes
On Quince Stock: Golden-Yellow,
Rose-tinted towards the Sun
Grammes
Average weight (of 10 Pears) 280 406
 Density of fruit " " 0.993 0.9987
" of Juice (at 15 C) 1.046 1.051
Acidity of juice (per litre) 1.070 1.196
Grape sugar, " " 92.406 90.486
Total sugar, " " 92.406 102.333
Ash 2.161 2.465

These figures, as above indicated, are rather intended for comparative purposes; and for this reason, as well as for the sake of simplicity, it has not been considered necessary to convert them into English equivalents. It will be observed that these results show, as regards the fruit obtained from the Triomphe de Jodoigne, grafted on Quince stock, a superiority in respect of, inter alia—

(a) Average weight; (b) density ; (c) proportion of free acid (expressed in terms of sulphuric acid); and (d) the total amount of sugar contained in the juice, a factor which, although the last-mentioned is not the least important. The difference, in fact, amounts to nearly nine grammes per litre of juice in favour of the fruit grown on the Quince stock. If the crop gathered from each tree be taken to consist of 300 Pears, each weighing 280 and 406 grammes respectively, the total amount of contained sugar would be represented by 7 kilos, (say 15 lb.) as regards the fruit grown on the Pear stock, and by 11 kilos, (say 24 lb.) as regards the tree grafted on the Quince.

MM. Rivière and Bailhache, moreover, record that certain analogous experiments conducted by them in 1886 and 1887 in relation to the Doyenné d'Hiver had given similar results as follows:—

Stock Average Weight of Fruit
Grammes
Percentage of Sugar in Juice
Grammes
Quince 435 11.59
Pear 230 9.64

The final conclusions drawn from these observations is, therefore, stated to be that the stock exercises a notable influence on the scion, inasmuch as it is apparently has the property of increasing or diminishing most of the physiological phenomena which take place through the agency of the scion, in the formation of the fruit.