SUMMARY 



103 



(/) Fruit of Divi-Divi, a West Indian tree, containing 

 30 to 50 per cent, of tannin; and of MyROBALANS, an Indian 

 and Chinese tree, 20 to 40 per cent, of tannin. 



(</) Acorn cups, called Valonia, of a certain kind of oak, 

 containing 25 to 35 per cent, of tannin. 



(h) Dried sap, called Kino, from Indian and African 

 trees, containing 75 per cent, of tannin. 



Fig. 24. — Hemlock bark and logs to be used for tanning. (Rhoads.) 



(i) Galls, or Nut Galls, a diseased excrescence on cer- 

 tain Persian and Turkish oak trees, caused by the sting of an 

 insect. Galls contain 60 to 75 per cent, of tannin. Tannic 

 acid is the purified form of tannin extracted from these galls. 



90. Summary. — The various plant compounds are classi- 

 fied as Carbohydrates, Fixed Oils and Waxes, Volatile Oils 

 and Resins, Nitrogenous Compounds, and Organic Acids 

 and their Salts. Carbohydrates comprise 72 per cent, of the 

 dry matter of plants. They are compounds of carbon, 

 hydrogen, and oxygen in which hydrogen and oxygen are 

 in the same proportion as in water. They, furthermore, 

 always contain one or more hydroxyl groups and usually 



