180 MEDICINAL AND POISONOUS PLANTS 



from the circumstance that they are commonly associated 

 in plants with volatile oils it is supposed that they are derived 

 from the latter by oxidation; but they are often complex 

 mixtures of obscure chemical composition. Comparatively 

 few resins are poisonous, and of these, only those contained 

 in the drugs called male-fern and Indian hemp need here 



Fig. 171, I. — Indian Hemp (Cannabis saliva, Mulberry Family, Moracea). 

 Staminate and pistillate plants. (Baillon.) — ^An annual 1-3 m. tall; 

 leaves roughish; flowers greenish; fruit dry. Native home, Central 

 Asia. 



concern us. It is the dried and pulverized underground stem 

 of the male-fern (Fig. 170) and related species which con- 

 stitutes the drug long known as a most valuable means of 

 expelling tapeworms. The resin, which is the active con- 

 stituent, has proved, however, in overdoses to be a violent 



