Essai sur la géographie des plantes; accompagné d’un tableau physique des régions équinoxiales.

One of the first works on the geographical distribution of plants. Humboldt was a pioneer student of geographical–ecological plant associations. The sheets of this work were reissued as Vol. I of the authors' Voyage aux régions équinoxiales du nouveau continent, fait en 1700, 1800, 1801, 1802, 1803 et 1804, with an extra half-title and general title and the plate colored. Digital facsimile of the 1805 edition from the Internet Archive at this link. English translation: Essay on the geography of plants, edited with an introduction by Stephen T. Jackson, translated by Sylvie Romanowski. Chicago: University of Chicago Press, 2009.