John Martyn's books, among them the Historia plantarum, also contain many of the earliest examples of color printing in botanical illustration. This image is a print, with added hand-coloring, showing the world as it was known at the time of publication (1741), while also illustrating the five zones of the world as described in Virgil’s Georgics.
Why was a botanist interested in this classical text? The Georgics is a work on agriculture, although it is much more than that: it contains some of Virgil's most beautiful poetry and considerations of the Roman Empire.