Opuntia Leptocarpa-Opuntia Velutina-Opuntia Megacantha

The Cactaceae : descriptions and illustrations of plants of the cactus family (1919)
Author: Britton, Nathaniel Lord, 1859-1934; Rose, J. N. (Joseph Nelson), 1862-1928
Volume: v.1
Publisher: Washington : Carnegie Institution of Washington
Year: 1919-1923.

Infographic | How the world's plant & animal genetic biodiversity helps feed the world

Foodtopia

Murray Bookchin - The Forms of Freedom

Prairie Studies, John Earnest Weaver, University of Nebraska 1932-52