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), Red Oak {Q. rubra), Scarlet Oak 

 (§. coccinea), Elack Oak (Q. tinetoria). Burr Oak (§. ma- 

 eroearpa), 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 Acacia (family LeguminQsm), grow- 

 ing in Australia, is- now extensively used in tanning. 

 The Mangrove bark (Rhieoplwra 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. 



Ufame of Plaint. Tannin. 



British Oak ( Quercus pedunculata, and Q. Robur) ... 10 per cent. 



Cork Oak (Qmrms Suber) 12 per cent,- 



Hemlock (Abies Canadenm) . 11 per cent. 



Mangrove-tree {Rhizophwa Mangle) 27 per cent. 



Red Oak (Qaefcus rubra) - 6 per Gent. 



"White Oak (Quercus alba) 8 per cent. 



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



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



Burr Oak ( Quereils macroecerpa) 8 per cent. 



275. The important dye, Quercitron, is obtained from 

 the Black Oak, Quercus tinetoria, 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. 



