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(horehound), a genus of plants of the family Labiatae. The plants are perennial or, less commonly, annual woolly herbs with opposite entire leaves. The pink, violet, white, or yellow flowers are gathered into dense false whorls in the axils of the uppermost leaves. The corolla has a flat upper lip. The fruit consists of four nutlets.
There are about 40 species, distributed in North Africa and the temperate and subtropical belts of Eurasia. The USSR has 15 species, growing mainly on dry slopes in the Caucasus. The most common species is the white-flowered common horehound (M. vulgare), which occurs in the western and southern regions of the European portion, in the Caucasus, and in Middle Asia. The plant usually grows near roads, in crops, on long-fallow land, and in wastelands. The common horehound contains a substantial amount of nectar. Many species contain tannin.