Mr. Knight, in the papers formerly communicated by him to the Royal Society, endeavoured to prove that the fluid by which the various parts added to trees, &c. are generated, has previously circulated through their leaves, either in the same or in the preceding season, and has subsequently descended through their barks. There is, however, a circumstance stated by Hales and by Du Hamel, which appears to militate against the above hypothesis, namely, that when two circular incisions are made, at a small distance from each other, through the hark, round the stem of a tree, and the bark between these incisions is wholly taken away; that portion of the stem which is below the incisions continues to live, and to increase in size, though much more slowly than the parts above the incisions. The above-mentioned naturalists have also observed, that a small elevated ridge is formed round the lower lip of the wound, which makes some slight advances to meet the hark and wood, projected in larger quantities from the upper lip of the wound. Our author, in a former paper, attempted to explain the above circumstance, by supposing that a small part of the true sap, descending from the leaves, escapes downwards, through the porous substance of the alburnum: in another paper he has shown, from the growth of inverted cuttings, the existence of a power in the alburnum to carry the sap in different directions; and he now describes some experiments made in order to show that the conclusions drawn by him are not inconsistent with the facts stated by Hales and Du Hamel; and that although the ascending sap usually rises through the alburnum and central vessels, yet the alburnous vessels appear to be also capable of an inverted action, when such action becomes necessary to preserve the existence of the plant.
Effects of using vegetative shoots of the preceding season on bur setting of Japanese chestnut trees.