139. XANTHORRHIZA.—YELLOW-ROOT. The rhizome of Xanthorrhi'za apiifol'ia L'Heritier. Habitat: Southern and Central United States. About 500 to 1,000 mm. (20 to 40 in.) long, and 10 mm. (⅖ in.) thick; externally of a bright yellowish-brown color; internally yellow; inodorous and bitter. Contains berberine, the alkaline base of berberis vulgaris; it is a matter of record that in many, perhaps most, berberine-yielding plants, a colorless alkaloid accompanies berberine, but, according to Lloyd, a second alkaloid does not exist in this drug. Used as a tonic. Dose: ½ to 1 dr. (2 to 4 Gm.).