Plants of the genus Aponogeton are strictly emersed and can not live out of water. They evolved in Australia then spread all over the world, fossils have been found in Peru, Labrador and Greenland; then migrated back to Australia, leaving species all the way there and back.
Aponogeton distachyos, described in 1792 is the foundation species and exists in the oldest fossils. More recent species have smaller and more complex flowers.
A. distachyos flowers are sold canned in South Africa where they are one of three ingredients in a regional lamb stew.