The evolution of the flora of the Great Basin appears to be closely paralleled in the development of semi-arid and arid floras in the rest of the world. The Early Mesozoic flora was dominated by gymnosperms that were replaced by the rapidly evolving early flowering plants ofthe Late Mesozoic. The flora of the Great Basin during the Cenozoic is a story of the evolution of flowering plants and their subsequent dramatic adaptations to desert conditions. The present desert flora appears to be derived chiefly from the Tertiary floras which ...