4 18 



MANUAL OF POISONOUS PLANTS 



_Fig. 198. European Aristolochia (Aristolochia Clem- 

 atitis). Flowering stem. Listed as a narcotic poison. 

 (After Faguet.) 



base; pistil 1 with superior ovary; fruit an achene; endosperm mealy. Con- 

 tains a single family (Polygonaceae). 



POI.YGONACEAE. Buckwheat Family 



Herbs, shrubs, or trees, often climbing; jointed stems; stipules in the form 

 of sheaths; juice often acrid or acid; leaves alternate or occasionally opposite; 

 flowers small, regular, mostly perfect; calyx more or less persistent; ovary 

 1-celled, bearing 2-3 styles or stigmas and a single erect ovule; fruit an 

 achene, 3-4-angled or winged, invested by the calyx ; embryo curved or nearly 

 straight; endosperm mealy, copious. About 800 species. Of economic import- 

 ance are the pie plant (Rheum Rhaponticum} ; and rhubarb (R. officmale} of 

 Thibet, the root of which contains cathartic acid and is a powerful cathartic ; 

 it also contains chrysophan C 27 H 30 O 14 , cmodin C 15 H.O (OH) 3 , rhein 

 C 15 H O.,COH) 4 and chrysophanic acid C ir .H 8 O.,(OTI) . It is purgative and 

 astringent. The canaigre (Rnmex Iiymcnoscpalus) produces a thick root valu- 

 able for tanning leather. It is a native of the southwest. The tannin is the same 



