418 



MANUAL OF POISONOUS PLANTS 



Fig. 198. European Aristolochia (Aristolochia Clem- 

 atitu}* Flowering stem. Ivisted as a narcotic poison. 

 (After Paguet.) 



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

 tains a single family (Polygonaceae). 



PoLYGONACBAS. 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 (i?. officinale) of 

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

 it also contains chrysophan C^^Hj^O,^, emodin CjjH^O„(OH)g, rhein 

 C,5HgOj,(OH)j and chrysophanic acid CjgHgO^COH)^. 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 



