the coat of Bark, and likewise by multiplying the roots, and thickening the spray and branches; and thus, the Proper vessels are prevented from being chilled, by untimely exposure. The fact, though universally known, is never referred to the true cause, by common observers.

These considerations furnish ample ground to admire the wise provision of Nature, in bestowing a much thicker, coarser, and more indurated covering of Bark upon all Trees in open exposures: For in vain might they possess every other property, if the vessels were not sufficiently protected, and enabled to do their office. Were that to happen, through the thinness of the Bark, there cannot be a doubt, but that the plants would become stunted and sickly, and both branches and spray would suffer injury in consequence, as we see happen to the generality of transplanted Trees, which do not possess this protecting property. From all which it appears, that the health and protection of the Proper vessels, by means of a due Thickness and Induration of Bark, is an indispensable prerequisite in all subjects meant for removal, and that it is deserving of the rank here assigned to it.

SECONDLY; Girth and Stoutness of Stem. Next to thickness of bark, the fitness of the Tree for removal greatly depends on this property. The Stem or Trunk of woody plants is classed, by Phytologists, among the Conservative Organs.

It is the part of the Tree, in which its bulk and strength principally reside, and has been represented, by Linnæus, as the Caudex ascendens, or Root above ground; an illustration, as Keith justly observes, more fanciful than philosophical.*

The Stems of Trees are augmented in width, by an annual layer, and, in length, by an annual shoot, springing from the terminating bud. The developement of the shoot from the Stem is not effected in the same manner as that of the root, by additions to the extremity only, but by the introsusception of additional particles, throughout its whole extent, at least, in its soft and succulent state. The extension of the shoot, as Du Hamel justly remarks, is inversely as its induration, rapid while it remains herbaceous, but slow as it is converted into wood. Hence moisture and shade are the circumstances of all others the most favourable to elongation, because they prevent induration or retard it. In close and confined plantations, therefore, where the external conditions of air and light are imperfectly supplied, the roots are correlatively proportional to the system of ramification. Trees so circumstanced push upwards to the light; and, from the warmth, which their situation affords, their stems being thin and slender in pro

* Physiolog. Bot. Vol. I. p. 43.

† Id. Vol. II. pp. 251, 252.-Kieser, Organ. des Plantes, p. 164. Also p. 166–168.

portion to their height, they are destitute of strength to resist the winds. The natural consequence is, that their roots are extremely apt to be shaken and displaced in the ground, and prevented from seeking proper food for the branches, and other parts of the Tree.

Now, it is obvious, that it is these very properties, which are the least adapted to removal. Nothing but a stem stout and vigorous, and nourished by adequate side-branches, can obviate the evils above delineated. Supports or props, whether composed of wood, cordage, or any other material, are of little avail in giving stability. To a Body, rather deficient in proper strength, a rich and favourable soil may, after some years, give an augmentation of roots and lateral branches, and, in the end, a certain accession of strength to the Body itself. But he, who would transplant with judgment, should consider a vigorous Stem, as a sine qua non in the beginning; as success otherwise must depend on accidents, which he cannot control, and on advantages, which he may not procure, at an after period.

THIRDLY; Numerousness of Roots and Fibres. Roots are also accounted among the Conservative organs. The body of the Roots of Trees, says Malpighi, may be regarded as a production and elongation of the trunk beneath the soil, and is constructed of the same textures, disposed in the

same manner.

Roots, like the stem, are augmented, in their width, by the addition of an annual layer, and, in their length, by the addition of an annual shoot, bursting from the terminating fibre; but they are elongated merely by the extremity.

As Trees have no organs analogous to the mouths of animals, they are enabled to take up the nourishment, which is necessary for their support, only by absorption and inhalation, as the chyle is taken into the animal lacteals, or air into the lungs. This, in the language of phytologists, is termed Introsusception; and the former mode, of course, applies to the introsusception of non-elastic fluids, and the latter to that of gaseous fluids. The fact is, that the Roots are much rather to be regarded as the mouths of plants, selecting what is useful to nourishment, and rejecting what is yet in a crude and indigestible state; the larger portion of it also serving to fix the plant in the soil, and to convey, to the trunk, the nourishment absorbed by the smaller fibres; which, ascending by the tubes of the alburnum, is thus conveyed to the leaves, the digestive organs of plants. † Roots, moreover, by their vigour and numbers, must previously stretch out under-ground, before the branches can

* Anat. Plantar. p. 145.

Keith, Vol. II. p. 246. Also pp. 90. 250.

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extend themselves in the air; and the progress of the latter developement will, of course, be in proportion to that of the former. By the curious and beautiful way, in which almost every part of a Tree modifies and determines the existence of every other part, as above noticed, the Roots, in their turn, receive vigour and extension from the advancement of the branches.

It appears, that Roots and Fibres are found more or less extensive, in the ratio of the exposure or shelter, in which a Tree is placed. In open situations, they are always strong and numerous, and they extend to a wide distance from the plant. This is indispensably necessary, notwithstanding the short and powerful stem, which a Tree so situated usually displays, in order to enable it to resist the elements, and to provide sustenance for the great expansion of top, with which such a Tree is sure to be furnished. Hence may be seen the great importance of numerous Roots and Fibres, in removing Trees of any magnitude. It is supposed by some, that the roots of Trees so placed, if of considerable age, after having exhausted, before their maturity, all the pabulum in their immediate neighbourhood, will at length be found searching for food, at a distance from the trunk, equal to the height of the Trees themselves. At all events, we are aware, that, even with Trees of a youthful age, the Roots and branches are co