any plant of the genus Solanum (family Solanaceae; q.v.), which has about 2,300 species, and certain other plants of the same family and other families. The species usually called nightshade in North America and England is Solanum dulcamara (see photograph-->), also called bittersweet and woody nightshade. Its foliage and egg-shaped red berries are poisonous, the active principle being solanine, which can cause convulsions and death if taken in large doses. The black nightshade (S. nigrum) is also generally considered poisonous, but its fully ripened fruit and foliage are cooked and eaten in some areas.