PUBLIC OPINION, p. 403 (25 September, 1902)

M. L. DANIEL, of the faculty of sciences of Rennes, has for some years investigated the question of vegetable grafting, and his researches have modified to a considerable extent our conception of this matter and the consequences of the operation. It was formerly believed that it was not possible, if one wished to obtain good results, to graft two closely allied plants, as, for example, two varieties of the same species. Daniel shows, however, that in point of fact it is possible to graft together two plants chosen nearly at hazard, the result depending more on the skill of the operator than on the nature of the plants, it being possible to unite by a graft two species of the same family, and even plants belonging to families which are widely different from each other. It is not necessary in this case to deal with ligneous plants, for the herbaceous species are as easily grafted as trees even at the time of their germination.

The principal conclusions of M. Daniel have reference to the action which the subject, the rooted plant, and the graft, the plant inserted into the former, have upon each other. It has been previously considered an article of faith that the graft only drew from the subject the superabundance of strength possessed by the former, and that the modification it underwent was but slight without any change taking place in structure or posterity. Daniel has shown in a convincing manner that the graft is often—not always—profoundly modified, that the subject is modified in its turn, and that by the graft it is possible to obtain new types which, being produced by the influence of two distinct plants, are partially comparable to those obtained by crossed fecundation. Daniel considers these new types as hybrids, which have no distinct sex. We will give a few examples.

The round yellow tomato, the large red early tomato, and the early red dwarf tomato constitute three types quite distinct from each other. Grafted on the round yellow tomato, the large red tomato takes the slender aspect, the color, and the disposition of the leaves of the subject, and in this case we have a very clear transmission of the characters of the subject race to the graft race. In the case of the round yellow tomato, grafted on the red dwarf early tomato, there is as remarkable a transmission in the characteristics of the fruit. On the same graft it is possible to observe at one time three different sorts of fruit; some are round, shining, and yellow, others are flat, shining, and yellow, and still others are flat-ribbed and yellow, thus combining the color of the fruits of the grafted race with the form of the fruits of the subject race. All of these fruits, with reference to size, are between the size of the fruits of the yellow round tomato not grafted and those of the red dwarf early normal tomato.

Daniel has also been able to graft the large red tomato on different aubergines. One of the grafts placed on the long violet aubergine (egg plant) obtained a much greater development than the others, and whereas the vegetable apparatus, outside of extraordinary vigor, kept its ordinary character, the fruit changed its form completely and acquired the lengthened and shining form of the aubergine subject, although it was much less long and large. The reverse graft of the aubergine on the tomato gave an equally original case. A long violet aubergine grafted on a large red tomato furnished at one time three kinds of fruit, some normal, shining, lengthened, and slightly pear-shaped others ovoid and shining, and a fruit flattened at the top and ribbed as the fruit of the tomato.

The following case is still more curious. There is at Brouvaux, near Metz, a medlar tree more than one hundred years old, which is grafted on a hawthorn, and a little above the graft the subject, that is the hawthorn, has given birth to a branch of medlar, this branch differing from the grafted part of the tree in the sense that it has thorns and that in place of producing single flowers the latter are united in an inflorescence having as many as twelve white flowers similar to those of the medlar. The fruits are those of the medlar, but they are very small and flat.

Graft of Egg-Plant on Tomato. At the left, normal fruit of the long violet an aubergine. In the middle, modified. rounded, ribbed fruit. At the right, modified fruit in the form of an egg.

These examples, taken from hundreds of similar ones, show in a conclusive fashion that the subject often modifies irregularly the specific character of the graft. A last question arises naturally in this connection, Are the modifications thus produced hereditary? From the experiments of Daniel one may conclude that the hybrids of the graft may be grouped in three categories: 1 those which integrally preserve their characteristics through grafting, slips, or tubers; 2 those which only conserve a portion of the acquired characters after this same vegetable multiplication; and 3, those with which the impression is fugitive and disappears totally when one attempts to multiply it by vegetative means. All of these facts, although irregular in their nature, are interesting from a practical point of view, but they are, above all, interesting from the standpoint of general biology.

Daniel bibliography