GUACO, HUACO or GUAO, also Vejuco and Bejuco, terms applied to various Central and South American and West Indian plants, in repute for curative virtues. What is most com monly recognized in Colombia as guaco is Mikania amara (Pl. equinox. ii. 84, pl. 105, 1809), a climbing plant of the tribe Eupa torieae of the Compositae, affecting moist and shady situations, and having a much-branched and deep-growing root, variegated, serrate, opposite leaves and dull-white flowers in axillary clus ters. The whole plant emits a disagreeable odour. It is stated that the Indians of Central America take guaco and boldly catch dangerous snakes, which writhe in their hands as though touched by a hot iron (B. Seemann, Hooker's Journ. of Bot. v. 76, 1853). The odour alone of guaco has been said to cause in snakes a state of stupor and torpidity ; and Humboldt, who observed that the near approach of a rod steeped in guaco-juice was obnoxious to the venomous Coluber corallinus, was of opinion that inoculation with it imparts to the perspiration an odour which makes reptiles unwilling to bite. The drug is not used at all in modern thera peutics.