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a genus of perennial herbaceous plants of the family Umbelliferae. The leaves are pinnate with entire or deeply separated segments. The petals are yellow and have recurved tips. The fruit is obovate or round. There are three or four species, found primarily in the Mediterranean area. One species, O. armeniacum, is found in the USSR, growing on rocky slopes in Armenia. The Mediterranean species O. chironium contains a substance in the roots that is used in perfumery.