from its fine and thin plates, which are thought to bear some resemblance to the leaves of a book. Or, it is more probable, that the Latin word liber took its name from this portion of the bark; in like manner as the English word book (from the Saxon boc), may, perhaps, be ultimately traced to the word Pak, or Pauk, which, in the language of certain Asiatic tribes, such as the Curdes, signifies the leaf (folium) of a vegetable. This will appear the less improbable, when it is recollected, how much it is the practice of some nations to change the P into B, and the latter into the former *: a practice particularly observed among the American Indians, and from a want of attention to which, it has often been supposed, that their languages, which are really closely-allied dialects, are radically different from each other. THE liber is the last layer of the bark, or that nearest to the wood. Like the bark itself, it is composed of a number of concentric net-works, placed one over the other. This part of the vegetable varies in regard to its appearance and quantity, in different vegetables. In the Lime or Linden-tree (Tilia) it is not very different from the wood. In general, it is more abundant in vigorous trees, than in those which are less vigorous, of the same species. In the spring-season, it is *In the language of certain American tribes (the Delawares and the Mahicans (Wuni-pak, and Waune pockq, are the words for the leaf of a vegetable. I have already mentioned the Asiatic word (Paul). It is remarkable, that Wan-noo is the trunk of a tree in the language of certain Asiatic Semoyads. "This coincidence between the languages of the American Indians and the people of the Old World, will not be deemed accidental, except by those whose prejudices render them incapable of judging. See my New Views, &c. pages, 75, 76, &c. more easily separated from the bark than at other times. At this time, also, it is more tender. When, in the progress of the season, it has acquired its peculiar or adult hardness, it forms the wood. In the ligneous or woody plants, it is not a difficult matter to fix upon the precise situation of the liber, in regard to the exterior bark and the blea, or the wood. Wounds in the bark heal more or less readily; the two lips or edges of the wound uniting together. In short, there is here a renovation of the bark. But the healing of a wound in the liber is essentially different from this; for here the wound forms a round edge, the two lips not uniting together. The liber, as we shall afterwards see, always finishes where the alburnum, or blea, begins. THERE is every reason to believe, that the complete developement of the liber forms the wood. The liber, like the wood, contains a great number of the vessels called trachea; but the exterior bark (cortex) con tains very few, if any, of these vessels. THE liber is, unquestionably, the most important portion of the bark. This is evident not only from its annual conversion into wood; but, also, from the injury which trees receive, when they have been deprived of their liber. The mere destruction of the bark is, indeed, a source of great injury to trees. Nevertheless, many vegetables continue to live and flourish, after very considerable portions of their exterior bark have been destroyed. This is said to be particularly the case in regard to the Apple-tree, the barking of which is found not only not to destroy the tree, but even to increase the chances of its life and vigour. But the destruction of the liber is always found to be highly injurious, and even generally fatal, to the tree. This is especially the case, when, along with the liber, we remove the blea. Trees rarely, if ever, recover, when these two parts have been destroyed in the same individual. Hence, the efficacy of the practice of girdling, as it is called, in the United-States. When the farmer wishes to cultivate a piece of ground that is covered with timber, the shade of which would be injurious to his grain or other vegetables, and if he does not find it convenient to cut down the trees, he proceeds to girdle them. This operation is performed by making with an axe, one or more complete circles through the bark and the liber of the trunk of the tree, and cutting some distance into the blea. Trees rarely survive this operation, especially if it have been performed early in the spring, before the first flow of the sap from the root towards the extremities. It is not uncommon, indeed, to observe trees, in foliage, though they have been girdled: but such trees very seldom live more than one year after the operation. It is proper, however, to observe, that different trees differ very greatly in regard to the duration of their life, after having been wounded, in the manner I have mentioned. In other words, some trees are very readily killed by girdling; whilst others survive this operation for a considerable time. Among the more hardy trees, or those which it is more difficult to kill by girdling, I * I know but two North-American trees, the shade of which is not injurious to vegetation. These are the Persimmon (Diospyros virginiana), and the Common-Locust (Robinia Pseud-acacia). It is at least certain, that the shade of these is much less injurious than that of other trees. may mention the Sugar-Maple (Acer saccharinum), and the Common Sour-Gum (Nyssa integrifolia). The Pines, in general, are readily destroyed, when they have been girdled. DURING the winter-season, the liber acquires neither firmness nor thickness; because during this season, the business of vegetation is, in a great degree, suspended. This observation, however, must be understood to apply to those climates only, which have a severe winter. THE liber, in some vegetables, is found to be the seat of certain properties which are not observable in any other part of the vegetable structure. Thus, the aromatic property of the Cinnamon-tree (Laurus Cinnamomum) seems to reside entirely in this portion of the vegetable fabric. In like manner, the colouring principle of many vegetables is entirely, or principally, seated in the liber. This is the case in the Quercus tinctoria*, and various species of Walnut and Hickery (Juglans), not to mention others. 4. IMMEDIATELY under the liber, or inner bark, we find, in many vegetables, particularly trees and shrubs, a peculiar substance, to which Linnæus has given the classical name of Alburnum: the "mollis ac pessima pars ligni", as Pliny calls it †. Linnæus defines it "the intermediate substance of the inner bark and the “wood”: “intermedia substantia libri & ligni ‡” • Dier's-Oak: commonly called Black-Oak, and Red-Oak, Philosophia Botanica, &c. THE Alburnum, which many English writers denominate the Blea, but which is better known in Britain and in the United-States, by the name of the "Sap", is the more soft and imperfect wood, which is generally of a whiter colour than the other wood, from which circumstance it has received its name of alburnum, or alburnus. By reason of its colour and its comparative softness, it has also been denominated the fat of trees, adeps arboThe French call this part of the substance of the vegetable, Aubier. In general, the sap is most conspicuous in those trees which have a very hard wood, such as the Oak and the Elm. It is, however, sufficiently conspicuous in other trees, the wood of which is more soft, such as the Tulip-tree (Liriodendron), the Pines (Pinus), Red-cedar (Juniperus virginiana), Lime-tree, and others. rum. THE sap, in the greater number of trees, is of a whiter colour and of an harder texture than the bark. It is found to contain lymphatic vessels, cellular matter, proper vessels, and utricles: but these are, in general, less perceptible in the sap than in the bark. The sap marks the disappearance of the bark, and the commencement of the newly-formed wood. When we cut a branch of an old tree, in the season of the running of the sap, we observe the vessels of the blea full of juice, discharging the contents at the cut*. THE sap may be distinguished from the wood by attending to the following circumstances. It has less density than the wood: its colour is brighter than that of the wood. It is less abundant in resinous matter, but Senebier. |