in botany: A genus of plants of the clas of diandria, and order of monogynia; and in the natural system arranged under the 40th order, Peronateae. There are 17 species, only one of which is a native of Britain; the officinalis, or common vervain, which grows on the road-sides near towns and villages. The leaves have many jagged clefts, the blossoms are pale blue. It manifests a slight degree of astringency, and was formerly much in vogue as a deobstruent; but is now disfavored. Mr Millar says that it is never found above a quarter of a mile from a house; whence the common people in England call it Simpler's joy, because, wherever it is found, it is a certain sign of a house being near. Sheep eat it; cows, horses, and goats refuse it.