188 MEDICINAL AND POISONOUS PLANTS 



from the bark of the CaHsaya-tree (Fig. 176) and related 

 species. Its great and -widely recognized value in the treat- 

 ment of malaria is explained by the fact that in quantities 

 not seriously injurious to a human being the alkaloid acts 

 as a deadly poison upon minute parasites which occur in 





FiCx. 176. — Calisaya-tree (Cinchona Calisaya, Madder Family, Rubiaceoe). 

 A, flowering branch, J. B, flower. C, corolla and stamens. D, fruit. 

 E, fruit with upper half of wall removed to show the packing of the 

 seeds. F, fruit, cut across. G, seed, enlarged, and cut through the 

 embryo, lengthwise. (Luerssen.) — Tree about 12 m. tall; leaves pale 

 green; flowers pink; fruit dry. Native home, Andes of Peru. 



the blood of malarial patients and are regarded as the cause 

 of the disease. It is highly valued also as a tonic. Its in- 

 tensely bitter taste is a property' familiar to most persons. 



Strychnine (CoiHocN.jO^), the principal alkaloid obtained 

 from the seeds of the nux vomica tree (Fig. 177), is one of 



