Gardeners’ Chronicle, (Ser. 3) 32: 409-410 (December 6, 1902)

SPECIFIC VARIATIONS CAUSED BY GRAFTING

WE have from time to time called attention to the very remarkable experiments in grafting made by M. Daniel, of Rennes, experiments so remarkable that a considerable amount of scepticism may naturally be expected with regard to them. We find in the Revue Horticole, for Sept. 1, an interesting article by M. Grignan, including a summary of some of M. Daniel's work, which, as it may be of interest to many of our readers, we reproduce, hoping that some of our cultivators may be disposed to repeat the experiments for themselves and to chronicle the results. It is needless to say how much practical importance attaches to these experiments. They afford another illustration of the urgent necessity for an experimental garden where such researches can be carried out in a man ner that is not practicable in purely business establishments.

M. Daniel grafted different varieties of Tomatos one upon another, and on the Aubergine, the Capsicum on the Tomato and on the Aubergine, Potatos one on the other, Pears one on another (principally by double grafting), Roses, various Composites, especially Sunflowers, also Crucifers, Cabbages one on another and on the Turnip, &c., Vines one on another, &c. In these different cases he obtained very marked and extremely interesting variations. Thus, the long violet Aubergine, grafted on the ribbed Tomato, yielded round ribbed fruit, new races were obtained, distinct and more or less intermediate in habit, flowers, fruit, tubers, &c.

Helianthus tuberosus (Jerusalem Artichoke) grafted on to H. annuus (annual Sunflower) yielded particularly interesting results; the annual habit became persistent, and showed in great measure the characteristics of the graft; adventitious roots appeared on the graft at the level of the swelling, and had partly penetrated into the tissue of the stock, and were completely blended with it.

The Medlar raised by MM. Simon-Louis, furnished M. Daniel with another well-marked example. Very interesting variations were observed also in the markings of the graft and the stock, in the time of the flowering, in fertility. All these facts briefly summarised led M. Daniel to conclude that grafting is not always a sure means of preserving the characteristics of varieties, races, or hybrids (though sometimes it is so), but perhaps it may occasionally be a fertile source of variation. M. Daniel had also recourse, in some experiments, to mixed grafting, which enabled him to regulate at will the flow of sap, leaving on the stock a number of leaves proportionate to the vigour of the graft.

The results here mentioned would have but a restricted significance if the specific variation were limited to individuals; but in many cases the acquired characteristics ware made permanent by buddng or grafting, or even preserved by inheritance. Thus it was that M. Edouard Lefort was able to render persistent a graft-hybrid in the shape of the Potato that bears his name, and which preserves blended the characteristics of the two component varieties, Marjolin and Imperator. M. Daniel obtained analogous results; he even fixed and propagated from seed a new variety originated by him, a cold-resisting Cabbage. M. Jurie fixed a variety of Vine, by budding and grafting. Other plants, Roses for instance, cannot be fixed; Aubergines and Capsicums did not furnish seed.

In some cases the results of the trials are not yet conclusive. M. Daniel grafted the wild on to the red Carrot; the seeds obtained yielded some annual, others biennial plants; some with three normal cotyledons, others with three cotyledons of which one was bifid; others with two cotyledons, one being bifid, and others again with a single cotyledon.

In fact, asexual hybridation, according to M. Daniel, is neither constant nor regular, nor very frequent. Sometimes it operates directly upon the grafted plants, sometimes indirectly upon their descendants; sometimes it affects external, at others internal characteristics; in some cases there is, as in Cytisus Adami, a disjunction or separation of previously blended characters; occasion. ally heredity and persistency are complete, sometimes partial or lacking. It is also often possible to achieve results already expected. But the most important feature from a practical standpoint, and one to which too much attention cannot be drawn, is that in many cases grafting has already served to ensure a systematic improvement of plants.

In this connection, we may note an important remark by M. Daniel: that when it is required to improve a plant in a certain particular, it must be grafted on to a stock that is superior in that respect. Thus, the author, when originating his breed of cold-resisting cattle Cabbage, selected as stock a Cabbage possessing that quality of hardihood, irrespective of its other characteristics.

As the graft may induce improvement, so it may also produce the contrary result. M. Daniel mentions this danger, with special allusion to the Vine. The grafting of French Vines, practised on a large scale consequent upon the Phylloxera ravages, caused, it seems, the crus, or superior wines, to disappear. This opinion is supported by that of MM. Gaston Bonnier, Bellot des Minières, Poubelle, &c. M. Daniel suggests, with M. Jurie, who is also experimenting in this direction, practical trials for the improvement of the Vine by systematic grafting.

The works of M. Daniel are likely to effect, among ancient and traditional doctrines, quite a revolution, but one which is not to be accepted without repeated investigation. His theories, though borne out by facts, are naturally regarded with doubt by some, or are only partly credited. Yet in practice they have been wonderfully justified.

Further confirmation is, indeed, afforded by the works of Herr Lindemuth, head gardener at the Royal University garden, Berlin, who has several times exhibited very interesting specimens of grafting at the exhibitions of the Royal Horticultural Society of Prussia. Herr Lindemuth published in the Gartenflora of January 1 last a note of the exhibits shown by him in the preceding October, and which may well be quoted here.

"The following were the grafts shown by Herr Lindemuth:—

"1st. Solanum erythrocarpum on S. lycopersicum (exceptional development).
"2nd. Yellow Wallflower on Red Cabbage. The flowering of the Wallflower was exceptionally early.
"3rd. Hybrid Petunia on Nicotiana.
"4th. Abutilon Thompsoni on Sida Napaea.
"5th. Malvastrum capense with yellow variegated leaves.
"8th. Althaea rosea with yellow variegated loaves.
"7th. Abutilon Thompsoni on Althaea narbonensis."

Nos. 4 and 7 require further comment.

"On August 2," says Herr Lindemuth, "I grafted two plants of Sida Napaea, both twenty cents. high (about eight inches) from the ground. The two plants were put in similar soil, and treated in the same way. The grafts have attained a length of twenty-five centimetres (about ten inches); they are fresh, and healthy. Each plant has produced three shoots on the stock. On one, the leaves of the shoots of Sida have become distinctly variegated; on the other they have remained green."

M. Daniel obtained analogous results from mixed grafting, and in his notes describes exactly the variation in the result under conditions that appear identical, although in reality these conditions are almost always different.

The other instance is still more characteristic. To quote Herr Lindemuth—"In August, 1900, I grafted Abutilon Thompsoni on young stocks of Althaea narbonensis, a plant closely allied to the common Marsh Mallow. The graft 'took' in a few days. The young stocks were nearly five months old; each had a single shoot, upon which the Abutilon was grafted. Two grafted specimens which did well passed the winter in a cool-house under favourable circumstances; both were put out in the open ground on May 18, 1901.

"On October 31, 1901, the graft of Abutilon on plant A was seventy-five cm. (thirty inches) long; it was vigorous, and bore healthy leaves. The stock Althaea narbonensis had put forth a shoot ninety cm. (thirty-six inches) in length, and branched, which is dead, and still bears ripe fruit.

"The plant is perennial; the shoots issuing from the ground in spring are annual, or, more properly speaking, half-annual; they appear in April, bloom, produce fruit that ripens, then die in September. Meanwhile, large dormant buds form at the base in the earth which produce new shoots in the following spring.

"Plant B has no shoot except the graft. The parasitic Abutilon has completely absorbed the stock in its own development, and has prevented it from putting forth any shoot; The stock, however, is avenged. The graft has grown, it is true; but half its leaves have already fallen, others appear sickly and begin to die. The parasite can no longer be sufficiently nourished by the stock without the aid of its shoots and its (the stock's) leaves, and is condemned to die with it.

"What scientific and practical conclusions can be drawn from this? The grafted shoots of both plants should, in accordance with their nature, have died in September, 1900; they still live, there is still an Abutilon Thompsoni alive among them, in one case (A) in perfect union and apparently complete vigour. The grafted stocks have, in the course of the year, run through all the stages of their natural existence, they are still fresh, and an interchange of nutritive and constituent elements is still maintained between the roots of the Althaea and the Abutilon graft.

"The results of these experiments lead to the following question: do the grafts of Abutilon and Althaea still grow, and is their existence permanent? Is it possible in certain or in many cases to blend successfully by grafting, annual or short-lived with perennial plants, and would annuals thus grafted live for several or for many years?"

We may add that Herr Lindemuth would not have suggested this last question if he had read the notes published by M. Daniel ten years ago. Apart from this, the grafts of Abutilon Thompsoni on Althaea narbonensis furnish a good instance of the differences yielded by mixed grafting (plant A) and ordinary grafting (plant B), and the more marked influence of mixed grafting.

The length of this note is justified by the importance of the subject—one of the most important, from a practical standpoint, in all gardening.

Daniel bibliography