Page:Proceedings of the Royal Society of London Vol 1.djvu/389

Rh such considerations, it is not improbable that, on the Contrary, some new light may be thrown upon the functions of the animal economy by investigations respecting those of vegetables, where the necessary experiments may be repeated any number of times, and where the inﬂuence of efﬁcient or defective organs may be observed with the most deliberate attention.

The parts separately noticed on the present occasion, are the roots, the stem, and the leaves. The roots and leaves have been compared by all naturalists, both ancient and modern, to the intestines and lungs of animals. The analogy also, between the sap of vegetables and the blood of animals, is very obvious; and the circulation of sap in the former, as far as is necessary to, or consistent with, their state of existence, is very satisfactorily established by the experiments for- merly communicated to us by Mr. Knight, in addition to those made by other naturalists.

With respect to the roots, no experiments appeared wanting to determine that no defect in the action of this organ occurs from age, and consequently that the debility and diseases of old varieties of fruit were not derived from this source. The duration of roots, in old coppices, that are felled at stated periods, appeared to the author sufﬁcient to establish that the quantity of produce is not diminished by age of the roots. The inability also, of a seedling stock to give the character of youth to an inserted bud or graft. seemed to prove how little is effected by undoubted youth of the root.

Mr. Knight ascertained, however, by an experiment of an opposite nature, that the stock may be affected by the graft. By planting cuttings of some very old varieties of apple. he obtained stocks which would soon have manifested the usual appearances of age. At the end of two years these were grafted, at about two inches from the ground, with new and luxuriant varieties; and at the end of ﬁve years the roots were examined, and were found to contain ten times as much albumum as they would probably have contained if they had not been grafted; and they were also wholly free from disease.

Another kind of experiment was next made upon the effect of grafting young wood upon old, the old having ﬁrst been grafted upon a young stock, in a situation where it would not have survived the second or third year. But when a. portion of an old golden pippin was thus included between two portions of a crab, the wood was found to grow just as well, and to be just as healthy as the stock and branches.

In other experiments the author tried the effect of placing young grafts upon old ones, that had long since become cankered. The old ones being cut off at the distance of a foot from their original junction, he regrafted them with new and healthy varieties, and he found that they became, in consequence, perfectly freed from every appearance of canker.

The author having thus ascertained that the debilities of old varieties of fruit-trees did not originate in any defective action of the