Exploring the Leiden ‘Van Royen herbarium’: History and scientific significance of the herbarium specimens of Adriaan (1704–1779) and David van Royen (1727–1799)

The dried plant collection, now known as the ‘Van Royen herbarium’, was assembled by Adriaan and David van Royen, successive Leiden professors of botany in the period 1729–1799. The significance of this herbarium is partly due to the fact that Linnaeus was able to study Adriaan’s collections extensively when he stayed in The Netherlands, such that it must have influenced, to some extent, his subsequent publications, notably Species Plantarum (1753). In this review we track the complex history of the herbarium and follow its physical housing through time. Poor storage conditions in the 18th and 19th centuries may account for the loss of an unknown number of specimens originally in the herbarium. The history of the herbarium of Nicolaas Meerburg, head gardener in the Leiden botanical garden from 1774–1814, where he had worked from 1752, is closely connected with that of the Van Royens, and is also discussed here. We explore the composition of the ‘Van Royen herbarium’ and document who contributed to it. Altogether 80 plant collectors or original herbarium owners are identified. For example, there is a substantial set of specimens collected by Carl Peter Thunberg in Japan and many specimens from the Cape region of South Africa, which must have been gathered by him during his first stay there. Another large set is that collected by Johann Gerhard König in Ceylon (nowadays Sri Lanka) and there are many specimens from the collections of Albrecht von Haller and Sébastien Vaillant. The herbarium contains several seed collections used for Joseph Gaertner’s De Fructibus (listed in Appendix 4) and also many specimens assembled by Adriaan van Royen for his Ericetum Africanum project. Last, but not least significant among the rest, there are specimens cut out of a book herbarium owned by Jacob Breyne with plants collected by Carolus Schweiker (or Sweiker) around Montpellier (France) in 1666. Information necessary for the correct attribution of specimens is presented, complete with information enabling attribution of individual specimens to their original owners. Example barcodes of specimens from individual contributors and their handwriting(s) can be found in Appendix 3. Brief details of the life and work of Adriaan and David van Royen is given in Appendices 1 and 2. The significance of the herbarium for the typification of Linnaean and other species names is discussed.