in the anatomy of plants, the exterior part of trees, corresponding to the skin of an animal. For its organization, texture, &c., see the article PLANTS.
As animals are furnished with a panniculus adiposus, usually replete with fat, which invests and covers all the fleshy parts, and screens them from external cold; plants are encompassed with a bark replete with fatty juices, by means whereof the cold is kept out, and in winter-time the epicle of ice prevented from fixing and freezing the juices in the vessels: whence it is, that some sorts of trees remain ever-green the year round, by reason their barks contain more oil than can be spent and exhaled by the sun, &c.
The bark has its peculiar diseases, and is infected with insects peculiar to it.—It appears from the experiments of M. Buffon, that trees stripped of their bark the whole length of their stems, die in about three or four years. But it is very remarkable, that trees thus stripped in the time of the sap, and suffered to die, afford timber heavier, more uniformly dense, stronger, and fitter for service, than if the trees had been cut down in their healthy state. Something of a like nature has been observed by Vitruvius and Evelyn.
The ancients wrote their books on bark, especially of the ash and lime-tree, not on the exterior, but on the inner and finer bark called phylla.
There are a great many kinds of barks in use in the several arts. Some in agriculture, and in tanning leather, as the oak-bark (A); some in physic, as the quinquina or Jesuit's bark, mace, &c.; others in dyeing, as the bark of alder, and walnut-trees; others in spicery, as cinnamon, cassia lignea, &c.; and others for divers uses, as the bark of the cork-tree, &c.
In the East Indies, they prepare the bark of a certain tree so as to spin like hemp. After it has been beat and steeped in water, they extract long threads from it, which are something between silk and common thread; being neither so soft nor so glossy as silk, nor so rough and hard as hemp. They mix silk with it in some stuffs; and these are called nillae, and cherque-muller.
Of the bark of a species of mulberry-tree the Japanese make their paper. See Morus.
In the island of O-Taheite, the natives make their cloth, which is of three kinds, of the bark of three different trees; the paper-mulberry above-mentioned, the bread-fruit tree, and the cocoa-tree. That made of the mulberry is the finest and whitest, and worn chiefly by the principal people. It is manufactured in the following manner. When the trees are of a proper size, they are drawn up, and stripped of their branches; after which, the roots and tops are cut off: the bark of these rods being then slit up longitudinally, is easily drawn off; and, when a proper quantity has been procured, it is carried down to some running water, in which it is deposited to soak, and secured from floating away by heavy stones: when it is supposed to be sufficiently softened, the women servants go down to the brook, and, stripping themselves, sit down in the water, to separate the inner bark from the green part on the outside: to do this, they place the under side upon a flat smooth board, and with a kind of shell scrape it very carefully, dipping it continually in the water till nothing remains but the fine fibres of the inner coat. Being thus prepared in the afternoon, they are spread
(A) The bark of the oak has been long used in tanning leather, and even thought essential to that operation; but a different substance has been lately discovered, which answers the purpose full as well, and may be procured at a much cheaper rate; we mean oak saw-dust, or the chips of oak reduced to powder. This valuable secret was purchased by the society for the encouragement of arts, &c.