This little picture is one variety out of many of the Passion Flower, Passifloria incarnata L. It is a perennial vine, and is native to America. It has large, beautiful flowers, though the photo here is small, and a berry-like fruit.
Scientific Information - It was listed in the National Formulary from 1916-1936. Though thorough study has been done on the actives in the herb, at the time the publication I am gathering my information from was written, the exact component that caused the primary action had not been isolated.
Studies in rats report it significantly prolonged sleep time and affected loco motor activity. It Italy, it is given to hyperactive children. Folklore claims the herb is a motor nerve depressant, that it aids with insomnia, and restlessness, neuralgia, convulsions, epilepsy, nervous tension, fatigue, and muscle spasms. Perhaps these claims are proven true by the studies on rats.
Personally, I have used Passion Flower in combination with other herbs for insomnia.
Some sources for Passion Flower: