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a genus of plants of the family Umbelliferae. They include perennial, annual, and biennial herbs with pinnatisect leaves. The flowers are white or pale pink, and the fruit has a thick, spongy pericarp. There are approximately 40 species, distributed primarily in the temperate zones of Europe and in the mountains of tropical Africa. About 11 species are found in the USSR, growing mainly in damp areas. Particularly widespread is the fine-leaved water dropwort (O. aquatica), which grows in marshes, along canals, on the shores of bodies of water, and in shallow standing or sluggish waters. There are terrestrial and aquatic forms, the latter having submerged leaves. All parts of the plants are poisonous, particularly the roots. The plants have been known to posion cattle, horses, and sheep.