A brief summary of the principal vegetation types of Amazonia is given. This is followed by a discussion on the origin of the flora in terms of recent discoveries such as: plate tectonics and the movement of continents, the Pleistocen and post-Preistocene climate changes which reduced the amount of forest in Amazonia, the application of the theory of island biogeography to some continental habitats such as savannas in Amazonia, the recent emphasis on plant-insect relationships, annd the availability of more detailed maps as a result of a radar survey of Brazilian Amazonia....