Olaf Hagerup

Olaf Hagerup (29 September 1889 – 2 March 1961) was a Danish botanist. He studied botany at the University of Copenhagen from 1911 under the professors Eugenius Warming, Christen C. Raunkiær, L. Kolderup Rosenvinge og W. Johannsen. He took his Ph.D. from the same university in 1930. From 1934 to 1960, he was superintendent at the Botanical Museum of the University of Copenhagen.

Hagerup’s scientific works concern evolution, polyploidy and pollination, among other things. He showed that the tetraploid Empetrum hermaphroditum is a separate species from the diploid Empetrum nigrum. He thereby initiated the use of chromosome numbers in systematic botany, a field later known as cytotaxonomy. He put forward the hypothesis that the ploidy level is an important factor in the distribution and ecology of plant species. In contrast, another of his scientific ideas has been disproven by later modern research – the idea of a direct ancestry of the centrosperms (approximately equal to Caryophyllales) from the gymnospermous Gnetophyta and, hence, two separate evolutionary lineages within the flowering plants. Many of Hagerup’s studies were concerned with plant species of the Ericaceae, Empetraceae and related families, or ’’Bicornes’’ as they were known in the Wettstein system.

The cranberry Oxycoccus hagerupii (Ericaceae) was named to his honour by Á. & D. Löve (later transferred to Vaccinium by Hannu Ahokas as Vaccinium hagerupii.