The British Cyclopaedia: Acacia.

The British Cyclopaedia
of the arts, sciences, history, geography, literature, natural history and biography; copiously illustrated by engravings on wood and steel by eminent artists.
Edited by Charles F. Partington, professor of mechanical philosphy, author of various works on natural and experimental philosophy, &c., assisted by authors of eminence in the various departments of science.
Complete in ten volumes.
Volume VI.
Natural history.
London: WM. S. Orr and Co., Amen Corner, Paternoster Row.
An extensive genus of exotic trees and shrubs belonging to the Linnaean class and order Polygamia Monaccia; and to the natural order Leguminosae, division Mimoseae, of Jussieu. The name is derived from the Greek word [-] to sharpen, in consequence of many of the species being, thorny. Generic character; flowers, polygamous; calyx, four or five toothed; the petals of the corolla four or five, at one time free, at another coalescing; stamens varying from ten to 200; pods not jointed, juiceless, and two-valved.

Branch of the Acacia. The species included under this genus are very numerous, amounting to about 300. They are shrubs and trees, varying in habit and foliage; and while by their beauty and elegance they contribute not a little to adorn the countries in which they grow, they are found to be of essential service in the arts and manufactures by supplying them with a hard, and durable wood, which is deservedly much valued. They are found in the tropical regions of Asia, Africa, and America, and also abundantly in New Holland, Van Diemen's Land, and New South Wales. They all bear pods like the pea family, but in their blossoms they have a considerable resemblance to the willow tribe. By their airy foliage and golden flowers they throw a charm even over the sterile deserts of Africa: —
"Our rocks are rough; but smiling there
Th’ acacia waves her yellow hair;
Lonely and sweet, nor lov'd the less
For flow'ring in the wilderness.”

The leaves are, as we have already stated, in the greater number of the species, pinnate, that is, having a central stalk and numerous small leaflets on either side of it, as represented in the engraving; in others, however, the leaf-stalks become dilated vertically into hard, leathery expansions, denominated Phyllodia, which seem to serve all the purposes of leaves, and which in their young state generally bear leaflets. From this difference in the foliage, the species have been divided into those having pinnate leaves, and those provided with phyllodia. The latter are of frequent occurrence in New Holland and the other parts of Australia, and may be said, in some degree, to characterise the vegetation of those countries.

We shall notice a few of the important species. The Acacia Arabica, vera, Senegalensis, and Nilotica, &c., are interesting in a commercial point of view, as yielding the substance called Gum-Arabic. This exudes either spontaneously or from incisions made into the bark, and subsequently hardens by exposure to the air. When pure it is transparent and colourless, has neither taste nor smell, and is perfectly soluble in water, forming what is called mucilage. Gum Arabic derives its name from having been originally brought from Arabia; subsequently, how ever, Africa, more especially Senegal, has furnished a considerable quantity. From this circumstance the name of Gum Senegal has been given to some varieties. The Gum Arabic tree is also found in the East Indies. The gum is collected in the months of December and January, and sold in large quantities to French and English merchants. It is capable of being used as an article of food, and is very nutritious. During the time of the gum harvest the collectors subsist upon it entirely, and six ounces are said to be the usual allowance for an adult, in the course of twenty-four hours. Gum is used extensively in medicine, as a bland mucilaginous substance, for the purpose of allaying various irritations. It is made into the form of lozenges and jujubes with several other substances. It is useful in the arts, being employed in calico-printing to give consistency to colours, and to prevent their spreading. For similar reasons it enters into the composition of writing ink, blacking, &c. Botanists employ it to fix the dried specimens of plants upon paper, and it is used in the formation of numerous fancy and ornamental articles, such as seals, rice boxes, &c. The bark of the Gum Arabic tree is employed in India as a tonic for strengthening the stomach, and a decoction of its pods serves for the purpose of washing.

Another species of Acacia, the Acacia Catechu, or Khair tree, a native of the mountainous parts of Hindostan, deserves notice chiefly on account of its yielding a substance which is used in medicine. This substance, which was formerly erroneously denominated Japan Earth, but now receives the name of Catechu, is an extract from the internal part of the wood of this tree prepared in Bengal, and other parts of India, by decoction and evaporation. The extract is also prepared from the pods of the tree, as well as from other plants, such as the Nauclea Gambic and Areca Catechu. It has a reddish brown colour, and its taste is very astringent. On account of its astringent property, it is used in various diseases as a medicinal agent of considerable efficacy.

The Acacia discolor, and several other species known in Van Diemen's Land, under the general name of Wattle, furnish much of the timber used in that part of the world.

From the bark of the Acacias, found in Van Di men's Land, more especially the Acacia decurrens and mollissima, an astringent extract was lately prepared and imported into Britain for the purpose of tanning leather. It was found, however, that the expence of the extract was far too great to render it a marketable commodity, and the bark itself is therefore now substituted. Occasionally a quantity of the Mimosa Bark, as it is termed in commerce, is imported into London. The bark is of little value in Wan Diemen's Land; and although the freight and duty are considerable, still so long as the Acacias continue to be cut down, in that country, for the purpose of clearing the ground for cultivation, the price must remain in some degree moderate. The Mimosa Earth is more astringent, and possesses a more powerful tanning property than the oak bark, but it imparts to the leather a reddish tint, which renders it fit only for sole leather. The Mimosa Bark, however, when mixed with acorns, may be used for the tanning of dressed leather.

The Acacia decipiens, found in New Holland, was formerly mistaken for a fern, and called fern-tree, on account of its long flowerless branches. The Acacia melanoxylon, denominated in Van Diemen's Land, Black-wood, is a beautiful tree, with foliage reaching to the ground. It grows to a considerable height, but does not attain a great diameter. Of late years various new species of acacia have been collected in Australia, by Mr. Allan Cunningham, Mr. Fraser, and Dr. Leber.

The acacias are propagated by seeds, or by cuttings ut into sandy soil, under a bell-glass, and kept warm. The flowers of some of the species of acacia are used by the Chinese for dying a yellow colour.

In our shrubberies the Robinia Pseudo-Acacia, or Locust-tree, an elegantshrub, bearing white pea-shaped blossoms, occasionally tinged with pink, is commonly cultivated under the name of Acacia.

For the better distinguishing this numerous family botanists have arranged the species into five divisions, founded on their different modes of foliation, and these divisions have again been subdivided into sections, founded on their manner of flowering, or on the absence or difference of their armature. A few of the species are climbers, and many, indeed a whole division, are marked dubia, not being sufficiently known to distinguish to which section they belong. The name Acacia has also been given to many other species of plants, viz. to a species of Darlingtonia, to a Gagnebina, and to several of the genus Prosopis.

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