T. mauritiana, “Jamrosa bark,” said to contain 30 per cent. of tannin.
T. Oliveri, Malay Archipelago, yields “Thann leaves,” from which an extract is made as a cutch substitute. A sample of the extract from Burmah examined recently in the Author’s laboratory, contained 62 per cent. of tannin. The tannin is a catechol derivative, differing from that of Acacia catechu in containing no phloroglucol ([p. 297]).
A sample of bark from Mandalay contained 31 per cent. of tannin, while the leaves from the same tree contained 14 per cent.
Emblic myrobalans, see [p. 293].
RHIZOPHORACEÆ, Mangles or Mangroves.
Rhizophora Mangle, and other allied species, Mangrove or Mangle, Manglier, Paletuvier, Cascalote, grows on tropical coasts all round the world. The barks vary much in strength, from 15 up to 40 per cent. in different species (see Ceriops). Leaves, used in Havana, are said to contain 22 per cent. tannin. According to Eitner, the younger plants contain the highest proportion of tannin. R. Mangle seems to yield a bark inferior to several other species.
All trees growing in swamp, and of the same character of growth as mangrove, are called “Bakau” in the East Indies (Anglice, mangrove) and various species of Ceriops yield the best tanning bark. A tidal mangrove swamp at low water is a tangle of arched roots like inverted branches on which the trees are supported.
The catechol-tannin, which is easily extracted, is of deep red colour and allied to that of the mimosas. In admixture with other materials the red colour has a much smaller effect, and mangrove bark is now largely used in combination with pine, oak and mimosa.
Several other species are also rich in tannin, and used in different parts of the world under the name of mangle, as are also several species of Conocarpus belonging to the Combretaceæ.
Rhizophora mucronata. India and Burmah. Bark varies considerably; David Hooper, Indian Museum, Calcutta, gives 26·9 per cent. of tannin. Dr. Koerner (Deutschen Gerberschule, Freiberg) analysed two samples in 1900, one containing 48 per cent. and the other 21 per cent. of tannin; two samples from the British Imperial Institute recently examined by the Author showed only 4·5 and 6·1 per cent. of tannin respectively.