ACACIA, a genus of shrubs and trees belonging to the family Leguminosae and the sub-family Mimoseae. The small flowers are arranged in rounded or elongated clusters. The leaves are generally compound pinnate (see fig.) ; in some instances more especially in the Australian species, the leaflets are suppressed and the leaf-stalks (petioles) be come vertically flattened, and serve the purpose of leaves. The vertical position apparently pre vents injury from the intense sunlight, as with their edges towards the sky and earth they do not intercept light so fully as ordinary horizontally placed.
leaves. There are about 55o spe cies of acacia widely scattered over the warmer regions of the globe. They abound in Australia and Africa. Various species yield gum. True gum-arabic is the product of Acacia Senegal, abundant in both east and west tropical Africa. Acacia arabica is the gum-arabic tree of India, but yields a gum inferior to the true gum-arabic. Catechu (q.v.) or cutch, is procured from sev eral species, but more especially from Acacia catechu; by boiling down the wood with this extract, true khaki cloth is dyed. The bark of Acacia arabica, under the name of babul or babool, is used in northern India for tanning. The bark of various Austra lian species, known as wattles, is also very rich in tannin and forms an important article of export. Such are Acacia pycnantha, golden wattle, A. decurrens, tan wattle, and A. dealbata, silver wattle. The pods of Acacia nilotica, under the name of neb-neb, and of other African species are also rich in tannin and used by tanners. The seeds of Acacia niopo are roasted and used as snuff in South America. Some species afford valuable timber; such are Acacia inelanoxylon, black wood of Australia, which attains a great size; its wood is used for furniture, and takes a high polish; and Acacia homalophylla (also Australian), myall wood, which yields a fragrant timber, used for ornamental pur poses. Acacia formosa supplies the valuable Cuba timber called sabicu. Acacia seyal is supposed to be the shittah tree of the Bible, which supplied shittim-wood. Acacia heterophylla, from Mauritius and Bourbon, and Acacia koa from the Sandwich Islands are also good timber trees. The plants often bear spines, especially those growing in arid districts in Australia or tropical and South Africa. These sometimes represent branches which have become short, hard and pungent, or sometimes leaf-stipules. Acacia armata is the kangaroo-thorn of Australia, A. giraffae, the African camel-thorn. In the Central American Acacia sphaero cephala (bull-thorn acacia) and A. spadicigera, the large thorn like stipules are hollow and afford shelter for ants, which feed on a secretion of honey on the leaf-stalk and curious food-bodies at the tips of the leaflets. In common language the term Acacia is often applied to species of the genus Robinia (q.v.) which belongs also to the Leguminous family, but is placed in a dif ferent section. Robinia Pseud-acacia, or false acacia, is cultivated in the milder parts of Britain, and forms a large tree, with beautiful pea-like blossoms. The tree is sometimes called the locust tree.