Synthesized answer
The provided passages do not contain enough information to answer the question about what evidence the author provides. The passages only state the title of the work, "Essai sur la géographie des plantes" by Alexander von Humboldt and Aimé Bonpland, and that it falls under the "Botany" category and has 168 pages [1]. There is no detail within these passages regarding the content or the evidence presented by the authors.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Essai sur la géographie des plantes by Alexander von Humboldt, Aimé Bonpland Categories: Botany Pages: 168