Herbarium P.E. Isert (1756-1789) and P. Thonning (1775-1848) Botanical Museum and Herbarium, Copenhagen
Between 1783 and 1803, when little was known in the field of tropical African flora, two Danes, Isert and Thonning made very important collections of plants in West Africa. About 2,000 specimens, representing over 600 species were received by the Professor of Botany at Copenhagen, Martin Vahl, who distributed many of them to contemporary botanists in other countries. It was possible to trace many of the duplicate sheets, which have been photographed for the microfiche collection, to Copenhagen, Paris, Berlin and Geneva.