TETRAGONIA, in botany; a genus of plants belonging to the class of icofandria, and order of monogynia; and in the natural system ranging under the 13th order, subculentae. The calyx is divided into three, four, or five parts. There is no corolla; the drupe is beneath, and the nut three or eight celled. There are seven species; the puticosa, decumbens, herbacea, celinata, expansa, crystallina, and the japonica.