Xanthorhiza n. : A genus of shrubby ranunculaceous plants of North America, including only the species Xanthorhiza apiifolia, which has roots of a deep yellow color; yellowroot. The bark is intensely bitter, and is sometimes used as a tonic.

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Taxonomy
Yellowroot, flowers, Xanthorhiza simplicissima, free encyclopedia, Search, stem, family Ranunculaceae, genus name, Native Americans, cultivation, adulterate, Duke, berberine, astringent, antimicrobial, anticonvulsant, bile, bilirubin.

Defination from the web:
Xanthorhiza, and one of very few genera in the family Ranunculaceae with a woody stem (the other notable example being Clematis) ... related to: Xanthorhiza simplicissima. Flora of North America: Xanthorhiza simplicissima. Description ...