This section is from the book "Harper's Guide To Wild Flowers", by Caroline A. Creevey. Also available from Amazon: Harper's Guide To Wild Flowers.
Color, bluish purple. Leaves, thin, serrate, those below petioled, heart - shape, or roundish at base; upper, ovate to lance - shape, entire, all with prominent veins underneath. Flowers, single in the upper axils. Nutlets, winged, each raised on an enlargement of the receptacle. May to August.
Rich, moist woods, New York, south to North Carolina and westward to Missouri. Found 3,000 feet high in Virginia.
 
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