Flower of a touch-me-not plant, Sri Lanka

"Mimosa pudica", is a creeping annual or perennial herb often grown for its curiosity value: the compound leaves fold inward and droop when touched or shaken, to protect them from predators, re-opening minutes later. The species is native to South America and Central America, but is now a pantropical weed. It grows mostly in shady areas, under trees or shrubs.