There are a vast number of bark and other substances useful for tanning purposes, which are found in the tropics, that are comparatively unknown or little regarded in Europe; but which might be readily obtained in large quantities and at a trifling cost.  The bark of many species of Acacia furnishes the tanning principle in a great degree, particularly that of A. arabica, which, under the name of Babul wood, is largely used about Scinde, Biliary, Gruzerat, and other parts of India; where it is regarded as a powerful tonic.  The fruit of A. vera, termed Egyptian and Senegal “bablah,” has been employed in tanning and dyeing.  Numerous species of this tribe are found abundant in New South Wales and the Cape Colony, and these, particularly the wattle bark of Australia, are in common use for tanning, from their astringent properties.  The bark and rind of the fruit of the pomegranate (Pumica Granata) have similar properties.

The bark of Avicenna tomentosa is in great use in the Brazils for tanning.  So are the curved pods of Caesalpinia Coriari, in the East and West Indies, under the name of Divi-divi. Coriaria myrtifolia is not only used in tanning leather, but also for staining black.  It is worth L9 to L10 per ton. Pterocarpus marsupium furnishes about Tellicherry the concrete exudation called kino, a powerful astringent used for tanning.

The plants of the mangrove tribe, Rhizophora Mangle, and other allied species, have frequently an astringent bark, which is in many cases used for tanning and dyeing black.  This tree is very common in most tropical countries, where it forms dense thickets on the muddy banks of rivers and the sea shores.  The bark of Bauhinia variegata, is made use of in Scinde and other parts of Asia.  The bitter astringent bark and the galls of several of the Tamarisk tribe are also well suited for the purpose.

Mesembryanthemum nodiflorum, one of the numerous indigenous species of the Cape, is used in making morocco leather.

The extract procured from the bark of the Butea, that of the Buchanania latifolia, the Scyzgium (Calyptranthes), Jambolana, &c., are likely to be of consequence to the tanners, and could be produced in India in large quantities.  Specimens of these, and of the bark of the Saul tree, of Nychanthes arbortrista, Terminalia angustifolia, and of the gaub fruit (Diospyros glutinosa), were shown by the East India Company.  The bark of the hemlock tree is extensively employed for tanning in New Brunswick.

The bark of yellow hercules (Xanthoxylum ochroxylon), and the pods of Acacia tortuosa are used for tanning in the West Indies.

In the instructions given by the Admiralty to Sir James Boss, when proceeding on his Antarctic Expedition, his attention was particularly called to the astringent substances adapted for tanning, and to the various extracts of barks, &c., imported into England from our Australian settlements, and which are employed by the tanner.  Little sterling information has as yet been obtained as to the qualities of the astringent gums, barks, and dyes, yielded in such abundance by the trees of those colonies, and the proportion of tannin they contained.