The diatom collection of Albert Grunow (1826-1914) at the herbarium of the Natural History Museum Vienna (W).

Albert Grunow (1826-1914) was a prolific diatomist, who described thousands of taxa. His work is foundational and greatly improved our knowledge of diatom taxonomy. Grunow's historical collection is still relevant for modern biodiversity research, as it includes many types and other historical material. Thorough taxonomic work considering type and other relevant original material is critical in view of the role of diatoms as aquatic bio-indicator species (e. g. for water quality monitoring purposes), Earth's history, and environmental change modelling. Here, we introduce the Grunow diatom collection at the Department of Botany of the Natural History Museum Vienna (herbarium W), its components and included object types, their organisation and management. The collection is complex for various reasons. For one, it encompasses a great variety of material types (e. g. loose diatomaceous earth in capsules; samples mounted on card, glass, or mica; microscope slides and other preparations; drawings; accession books (= catalogue); literature annotated by Grunow). Second, its components are interlinked and need to be considered together for identifying and locating specimens, which therefore involves a series of steps. Third, Grunow's collection includes a lot of material sent to him by other collectors, resulting in various numbering systems for collector vs sample numbers that need to be reconciled, often across multiple institutions. The aim of this paper is to detail this complexity for facilitating material requests to the W herbarium by giving a step by step example pinpointing original and other historical material of Achnanthes inflata (KÜTZING) GRUNOW. This shows how such material is located in the collection, so requesters know which information to supply to speed up a search within the diatom collection. [ABSTRACT FROM AUTHOR]