VEGETABLE POWDERS 



521 



Fig. 191. GUM TRAGACANTH. A bit of the gum mounted in water and 

 examined under a medium power, a, the gum presents a somewhat striated 

 appearance, interrupted by organic matter which takes on a bright yellow colora- 

 tion with tincture of iodine (c); b, groups of simple starch granules are distributed 

 through the gum. The better the quality of tragacanth the fewer the starch 

 granules, but even the highest grade contains some starch. 



