418 



MANUAL OF POISONOUS PLANTS 



Pig. 198. European Aristolochia (Aristolochia Clem- 

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

 (After Paguet.) 



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. officinale) of 

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

 it also contains chrysophan C 2? H 30 O 14 , emodin C 15 H 7 O (OH) 3 , rhe'm 

 C 15 H 6 O 2 (OH) 4 and chrysophanic acid C 15 H g O 2 (OH) 2 . It is purgative and 

 astringent The canaigre (Rumex hymenosepalus') produces a thick root valu- 

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



