648 BOTANY AND PHARMACOGNOSY. 



color. On drying they become yellowish or dark brown and much 

 shrivelled externally. Texas nutgalls are formed on the live 

 oak {Quercus virens) and yield 40 per cent, of tannic acid. 

 California oak balls are excrescences on Quercus lobata and 

 are about 5 cm. in diameter, and said to contain considerable 

 tannic acid. 



Other tannin-yielding plants are found in the following fam- 

 ilies: Combretaceae (p. 348), Leguminosse (p. 292), Myrtacese 

 (P- 346). 



CAMBOGIA.— GAMBOGE.— A gum-resin obtained from 

 Garcinia Hanhuryi (Fam. Guttiferae), a tree (Fig. 168) found 

 growing on the Malabar coast and in Travancore (p. 335). Spiral 

 incisions are made in the bark of the trees, and the gum-resin 

 which exudes is collected in hollow bamboo stems; it is then 

 allowed to dry slowly, after which the bamboo is removed. It 

 is chiefly exported by way of Singapore and is known commer- 

 cially as pipe gamboge. 



Description. — In cylindrical pieces, frequently hollow in the 

 center, of variable length, 2 to 5 cm. in diameter ; externally gray- 

 ish orange-brown, longitudinally striate, due to the ridges on the 

 inner surface of the bamboo canes in which they have been dried ; 

 hard; fracture short, the fractured surface being orange-red, 

 waxy and somewhat porous ; inodorous ; taste very acrid. 



The powder is bright yellow, sternutatory, and contains few 

 or no starch grains ; not more than 25 per cent, should be insolu- 

 ble in alcohol. The resin is soluble in solutions of the alkalies, 

 with the production of an orange-red color. 



Constituents. — Gum allied to arabin, 15 to 20 per cent.; a 

 resin known as cambogic acid, about 75 per cent. ; a volatile oil ; 

 ash, I to 3 per cent. 



Cake gamboge is collected in Saigon and Cochin from the 

 same plant that yields pipe gamboge. The product is, however, 

 collected in leaves and then allowed to dry. It occurs in irregular 

 orange-red masses, weighing i to 2 K., and is not so brittle as 

 pipe gamboge, but is less uniform in composition and may contain 

 impurities. 



Allied Plants. — A drastic gum-resin is also obtained from 

 Garcinia Mprella and other members of the Guttiferae, of India 



