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Evening primrose flower (Oenothera biennis). This plant has been used for centuries for its medicinal properties. The oil extracted from it is taken as a sedative, and it is said to be a good treatment for menstrual pain, skin disorders (such as eczema) and indigestion. The plant is native to North America, but now grows throughout much of Europe as well. (KEYSTONE/SCIENCE PHOTO LIBRARY/GUSTOIMAGES)