The index transcribes Humboldt’s global vision of Nature but according to our interpretation of geography of plants. It is finally a synthetic interpretation of Humboldt’s treaty. To do so, we decided to set up a double entry table with the species name and the physical variable of the environment. It was important for us to make a link from Humboldt’s orginal text to our new version of his observation. So because it was possible to create links by line, and so by plants, from the index to the Twine transcription we added each plant URL in the Twine HTML when a plant name appears to make physically the link between both part of our digital object.