170 MEDICINAL AND POISONOUS PLANTS 



Volatile oils form the most important constituent of a 

 number of non-poisonous drugs which we have already stud- 

 ied in the last chapter as food-adjuncts; nameh', lemon, 

 caraway, anise, cardamoms, spearmint, sage, ginger, and 



Fig. 163. — -Medicinal Rhubarb {Rheum officinale. Buckwheat Family, 

 Polygonacew) . Plant in flower. A, flower, entire, enlarged. B, same, 

 cut vertically. C, pi.stil; d. nectar glands. (Baillon.) — Perennial 

 herb growing 2 m. tall; leaves hairy; flowers greenish; fruit, dry, red- 

 dish. Native home. Central Asia. 



hops. The drugs calamus, asafetida, and saffron are the only 

 others of this class which call for mention here. Calamus 

 consists of the underground stem of the sw^eet-flag (Fig. 167). 

 It contains about 1% of a volatile oil to which it owes 



