Horse-radish (Cochlearia Armoracia), a perennial cruciferous plant native to eastern Europe, which has escaped from cultivation in England. It has a thick yellowish-white root with an acrid odour and pungent taste, for which the darker-coloured root of Aconite (q.v.) has been sometimes fat-ally mistaken. The horse-radish has large, oblong, serrate radical leaves, sometimes irregularly cut, and numerous small white flowers. The root, which is used as a condiment with roast beef and to a slight extent medicinally, owes its pungency to oil of mustard.