The volume and whereabouts of Humboldt and Bonpland’s botanical collections

Humboldt and Bonpland are often said to have collected 60,000 plant specimens representing 6,000 species. I review Humboldt’s estimates of the material collected in the Americas, discuss its whereabouts, and explain the difficulty in estimating specimen and species numbers due to problems with duplicate numbering. This led to at least 250 species being described twice. Based on field notes, they made 4,528 collections, aiming at three duplicates each. Of these, 3,525 survive in the Paris Bonpland herbarium, plus an unknown number in the general herbarium. Other herbaria are not yet fully digitized. Humboldt’s estimate (around 1800) of 4,200 species seems high, but the description of new species remains incomplete.