THE CORTEX, OR BARK. 293 



important tanning barks is furnished by Willows. In this 

 country most of the bark used in tannery comes from 

 White Oak (Q. alba), Eed Oak {Q. rubra). Scarlet Oak 

 ( Q. coccinea). Black Oak ( Q. tinctoria), Burr Oak ( Q. ma- 

 croearpa), the Hemlock {Abies Canadensis), and Birch 

 {Betula alba). The Oak and Hemlock barks make the 

 leather firm and hard, and give good weight. Mimosa 

 bark, from species of Aca^a (family Leguminosce), grow- 

 ing in Australia, is now extensively used in tanning. 

 The Mangrove bark (Bhizophora Mangle) has been much 

 used, but the leather obtained from it is inferior in color 

 and quality. The Mangrove-tree grows in low places in 

 all tropical countries. The table below gives the percent- 

 age of tannin in the barks most commonly used. It is to 

 be remembered, however, that the absolute amount of tan- 

 nin does not determine the color, solidity, pliability, and 

 other properties constituting good leather, which are also 

 to be considered in selecting tanning materials. 



Name of Plant. Tannin. 



'British Osik {Quercus pedunculata, and Q. Robur) . . . 10 per cent. 



Cork Oak (Qitereus Suber) 12 per cent. 



Hemlock (Abies Canadensis) 11 per cent. 



Mangrove-tree (Rhizophora Mangle) 27 per cent. 



Eed Oak f Quemis rubra) 6 per cent. 



"White Oak ( Quercvs alba) 8 per cent. 



Black or Quercitron Oak ( Q. tinctoria) 7 per cent. 



Mimosa (Acacia dealbata, etc.) 27 per cent. 



Burr Oak ( Quercm macrocarpa) 8 per cent. 



275. The important dye, Quercitron, is obtained from 

 the Black Oak, Quercus tinctoria, a North American tree, 

 growing to a height of eighty to ninety feet, and attaining 

 a diameter of four or five feet. The bark is deeply fur- 

 rowed, of a deep brown or black color, and yellow within. 



