TRAGACANTHA. GUM TRAGACANTH. 35 



widely used in English commerce mixed with Soudanese 

 varieties. Mesquit gum is derived from a number of 

 species of Prosopis of the MimosecB, plants allied to the 

 Acacia and found in the west and southwest part of 

 Texas and California, Mexico and South America. It 

 is often mixed with the lower grades of gum arable. 



TRAGACANTHA. GUM TRAGACANTH. 



A gummy exudation from Astragalus giumnifer, Labill., 

 and other species of Astragalus. (Nat. ord. Leguminoseae.) 



In narrow or broad bands, more or less curved or 

 contorted, marked by parallel lines or ridges, white or 

 faintly yellowish, translucent, horn-like, tough, and 

 rendered more readily pulverized by a temperature of 

 50° C. (122° F.). 



The species of this genus Astragalus are very numerous 

 in Asia Minor, at least thirty in number, and of charac- 

 teristic appearance. The gum is obtained by natural 

 exudation, or from cuts in the bark of the stem or 

 branches.* 



The form of the exudate, which is a product of degen- 

 eration in the cells of the pith and medullary rays, in 

 part, is due to the kind of incision, and varies according 

 to the conditions of heat and moisture. At times it 

 exudes in flattened, ribbon-like, irregular worm-like, 

 or spherical masses. After drying, the pieces have a 

 homy consistency, are whitish to brownish yellow con- 

 torted broad or narrow ribbons or irregular pieces, 

 marked with longitudinal lines. The tragacanth is 

 sorted and the different qualities determined by the size 

 and color of the pieces. 



It is tough, not easily cut nor powdered, save at an 

 increased temperature; pure tragacanth should be 

 tasteless, but often it is bitterish from portions of the 

 rind. It swells with water into a gelatinous mass. 



♦ Wiesner: Die Rohstofle, p. 112, Fig. 23. (After Tschirch.) 



