ACACIA ARABICA Willd.—Gabaruwa, Bagaruwa. LEGUMINOSAE.
This tree, the original source of gum-arabic, is very common and widely distributed throughout the north. It is very frequent round towns where it is utilised for the tannin properties of its pods. It varies largely in size from a small erect tree with umbrella crown to a large, heavy-stemmed tree with high rounded crown. It occurs gregariously in clumps or small forests, growing densely with the crowns meeting overhead. The seed germinates freely in low-lying country liable to submergence by rains or floods and the tree flourishes in such situations. It is just as partial to dry sandy soils where it abounds. With its almost black stem and branches, bluish-green foliage and graceful, symmetrical form, it is readily distinguished from other Acacia species. The average height is some 20-25 feet, but trees over 35 feet with girths up to 8 feet are not uncommon.
The Bark is almost black, or a dull dark grey, with long stringy ridges and narrow fissures. The dark colour extends to the branches and woody twigs, the latter covered with a soft pubescence. A clear yellow gum exudes from the slash which is a pale pink colour. The slash is red brown and blackish in streaks.
The Thorns are in pairs on the branches and twigs, some quite short and slightly curved, others, especially on the older wood being long, straight, slender and very sharp, with a grey colour and a slight backward slope. They are up to three inches in length and generally curved a little.
The Wood is a deep red-brown with almost purple bands. The sapwood is yellow. In transverse section the colour is darkest, the rings show as dark, ill-defined bands, the pores are small, few and scattered about between the fine straight rays which are visible against the dark ground of the hard tissue. There are many double and nested pores and zones with very few pores. Their contents nearly close them. In vertical section the grain is twisted, there are dark bands and the pores have black contents. The wood is very hard to saw and plane but the finish is hard and takes a high polish. The grain picks up badly in places. The transverse section will polish. The weight is 75-80 lbs. a cubic foot.
The Leaves are bipinnate, some 2-4 inches long with 5-6 or sometimes more pinnae bearing 15-20 pairs of leaflets with rounded tips, ³⁄₁₆ inch long. They are a dark bluish-green with grey bloom and soft texture.
The Fruits are jointed pods, straight or sickle-shaped, with slightly embossed seeds. The pod surface is wrinkled and covered densely with a whitish bloom. The seeds, some 10-12 in a pod, are round, flattened, shiny and brown, ⅜ inch in diameter. The pods, ripening towards the end of the year, fall to the ground entire. They are the “Sant Pods” of commerce.
Uses.—Hoe and axe handles are made from the wood which rarely reaches large enough dimensions to provide canoes as it does in other parts of Africa.
A concoction of the pods, crushed with water, is used for tanning. The leaves, boiled, with the addition of a small piece of Tamarind pod, are used as a cure for a disease of the eye which causes the lashes to fall out.