It is less well-known that Humboldt spent the next decades trying to expand his early findings in tropical America into a global plant geography. The first volume of the series "edition humboldt print" from the Academy Project "Travelling Humboldt – Science on the Move" of the Berlin-Brandenburg Academy of Sciences and Humanities is dedicated to Humboldt’s unpublished manuscripts on this subject: "Geographie der Pflanzen", edited by Ulrich Päßler (J. B. Metzler / Springer Nature 2020).

The edition presents manuscripts – many of which have now been published for the first time – that show Humboldt not as a traveling researcher in the field, but rather as a scholar at his desk in Paris and Berlin. It was in these cities where Humboldt collected data from around the world in order to determine global laws of plant distribution (fig. 2). His statistical method, which Humboldt called "botanical arithmetic," opened a new perspective into the complex biodiversity of the Earth, thereby also influencing the later work by Charles Darwin (1809-1882) on evolutionary biology.

The letters, lecture manuscripts and notes collected in this volume highlight the extent to which Humboldt’s scientific practice depended on vigorous intellectual exchange with colleagues, particularly those in France and Great Britain, as well as on the collaboration with assistants who too often go overlooked in research on Humboldt. One of these collaborators was the Leipzig-born botanist Carl Sigismund Kunth (1788-1850), who worked in Paris to evaluate the botanical collection of Humboldt and his travel companion Aimé Bonpland (1773-1858). Together with Kunth, Humboldt planned in 1825 to undertake a comprehensive representation of plant geography of the entire world.

The failure of this ambitious book project, which has largely been forgotten today, was due in part to the flood of data that could no longer be managed with the tools of the time. More than this, however, it was Humboldt’s ambition as a scientific writer to attain an elusive combination of science and aesthetics that ultimately hindered the work’s completion. His aim was to use artistic means to vividly depict the physiognomy of plants and landscapes of the globe. The young landscape painter and traveler in Brazil, Johann Moritz Rugendas (1802-1858), provided early drafts of such a pictorial representation of scientific data, but these never reached a public audience during Humboldt’s lifetime (fig. 3).

The materials related to this unpublished work (fig. 4) have now, for the first time, been presented in a scholarly edition, shedding light on Humboldt’s views on biological research in Europe and America around 1825. Furthermore, the edited collection makes visible the fascinating scientific paperwork practices, through which the authors Humboldt and Kunth collaboratively developed, exchanged, and reworked ideas in the form of paper slips and notebooks.