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a genus of annual grasses of the family Saxifragaceae. They are often (with the genus Lepuropetalon) distinguished as the separate family Parnassiaceae. There are 55 varieties in the temperate and subtropical regions of the northern hemisphere. There are four types in the USSR; of them, the most widely distributed is the swamp whiteface (P. palustris), which grows in damp fields, brush, and swamps. This is a graceful plant 15–40 cm. high, with a rosetta of leaves near the roots and single white flowers with five petals on the ends of the stems. The other varieties are found in tundra and alpine and subalpine mountain meadows.