6io BOTANY AND PHARMACOGNOSY. 



fers from rhanmetin found in the fruit of Rhanuius cathartica in 

 that the latter is crystaUine and forms a fluorescent solution with 

 sulphuric acid; senna-isoemodin (isomeric with senna-emodin), 

 which is soluble in petroleum ether ; cathartic acid ; calcium 

 oxalate ; and ash lo to 12 per cent. The active principles of senna 

 are emodin, chrysophanic acid and cathartic acid. The percentage 

 of emodin is from 0.8 per cent, in Tinnivelly leaves to i per cent, 

 in the Alexandria variety. 



Allied Plants. Senna pods (Fig. 262), derived from both 

 C. acutifolia and C. aiigitstifolia, are also found in the market, 

 either admixed with the leaves or sold separately ; they are from 

 3.5 to 7 cm. long and about 2 cm. broad, greenish to dark brown 

 externally, and contain from five to seven obovate, dark brown, 

 nearly smooth seeds. They contain apparently the same active 

 principles as the leaves. 



Similar principles are found in other species of Cassia, espe- 

 cially in the American senna (C. niarilandica), which is an 

 herbaceous perennial (Fig. 152), indigenous to the Eastern and 

 Central United States and Canada, with 12- to 20-foliate leaves, 

 yellow flowers and a linear, slightly curved legume. The leaves 

 of senna are sometimes admixed with those of Cassia ohovata, 

 which are broad and obovate, while the pods of the latter species 

 are distinctly curved. Mecca or Arabian senna is obtained from 

 a variety of C. aiigiisfifolia, growing in Arabia. The leaves of 

 C. holoscricca. of Abyssinia, are quite hairy and found occa- 

 sionally in the market under the name of Aden senna. The 

 leaves of other members of the Leguminosge are used like senna, 

 as Cytisus pitrgans of Southern France, Tcphrosia ApoUinca of 

 Egypt, and Colnfca cruenta of the Caucasus region. 



The root of Viviania esculenta (Fam. Geraniaceae), of the 

 East Indies contains a principle resembling cathartic acid, a gluco- 

 side also found in senna and rhubarb. 



HAMAMELIDIS FOLIA. WTTCHHAZEL LEAVES. 

 The leaves of HarnaincUs virginiana (Fam. Hamamclidaceae), a 

 shrub (Fig. 264) indigenous to the Eastern and Middle L'^nited 

 States and Canada (p. 286). The leaves are collected in autumn, 

 and are used in the fresh condition, or dried ; when dried they 

 should be carefully preserved and not kept longer than one year. 



