High Quality Content by WIKIPEDIA articles! Pisonia is a genus of flowering plants in the four o`clock flower family, Nyctaginaceae. It was named for Dutch physician and naturalist Willem Piso (1611-1678). Certain species in this genus are known as Catchbirdtrees because their sticky seeds reportedly trap small birds. Such sticky seeds are postulated to be an evolutionary feature of some island species for adherence of their seeds to birds; thereby facilitating dispersal of seeds between islands. These include P. brunoniana of Australasia and Polynesia and P. umbellifera, which is widespread in the tropical Indo-Pacific region.