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Acacia trees belong to the botanical familly of Leguminosae, predominantly species of the groups Fabales and Gummiferae. There are more than two hundred species of Acacia, out of which only ten produce gums with different properties.
The only species producing sap eligible for the name Acacia gum (or gum arabic) are Acacia senegal and Acacia seyal , which are further divided into several varieties (for instance kerensis or rostrata for A. senegal and fistula for A. seyal). Acacia gum is also known as Gum arabic, Gum acacia, Gum mimosa, Gummi mimosae, Gummi arabicum.
The trees have leaves of the bipinnate variety and long spikes or globular heads of flowers, generally of a yellow color. They are more or less thorny, from the fact that the stipules are often transformed into spines. They all delight in dry, sandy situations, and will often be found where other shrubs and trees can not exist.
The Acacia Senegal is a moderate-sized tree, usually about 20 feet high. It has a crooked stem with a grayish bark, and is much branched; the limbs being scattered over or covered with a purplish or yellowish-green bark. The leaflets are oblong-linear and arranged in eight or ten pairs. The spines are sharp and in two pairs. The flowers, which are small and yellow, are densely crowded on axillary, stalked, globose heads, usually two together. The fruit is a smooth, compressed, moniliform legume, of a light-brown color, and usually about 5 inches long, containing about 6 flattish seeds.
The gums yielded by Acacia senegal are known as the Kordofan and Senegal gums. This gum was historically one of the chief productions of the French colony of Senegal, being gathered by the natives in the section north of the river of that name. Nowadays, Sudan is by far the largest producer of this quality. The gum is gathered from November to July and shipped to France by CNI.
One of few strongly gregarious sahelian tree species, Acacia seyal combines tolerance of periodically inundated heavy clays with major roles in fuel and fodder production in countries at the southern edge of the Sahara desert, especially Mali, Chad and Sudan. The epithet seyal derives from an Arabic word for "torrent" used for the species in Egypt and denotes association with water courses.
The range of Acacia seyal extends from Senegal eastwards to western Somalia and the coastal lowlands east of the Red Sea, and from the Nile valley of southern Egypt to southern Zambia.
The species usually reaches 9-10 m in height at maturity and in well-formed individuals a flat-topped crown develops.
Seyal gum is not harvested in the same manner as Senegal gum . Instead of tapping the tree to develop the gum tear, Acacia seyal is exuded through naturally occurring breaks or fractures in the tree branches and bark.