Povl Klavsen (Paul Klausen), 1851-1925

by Brian Stevenson
last updated August, 2020

Povl Klavsen was a Danish school teacher who became an expert professional mounter of diatoms. Although his slides are relatively uncommon nowadays, he produced substantial quantities of diatom slides during the late 1800s and early 1900s, among which were strews from specific areas, arrayed type slides (“typenplatten”), and geometric arrangements of diatoms. A large proportion of Klavsen’s slides are currently held in museums, but they are occasionally seen in private collections (Figure 1).

Povl was born on October 6, 1851. His first wife, Charlotte, died in 1881 in Odense, Denmark. He remarried in 1883, to Marie Augusta Haugaard, in 1883. They had four children, two girls and two boys.

The Algal Herbarium of the Natural History Museum of Denmark reports that their collection of Klavsen’s specimens date from between 1878 and 1918, and consists of “Diatoms, mainly raw and rinsed samples. Neatly arranged diatoms”. Advertisements for sales of Klavsen’s diatom slides are known from American and German-language publications from the early 1890s through the 1900s (Figures 2-6).

Klavsen died on October 18, 1925, in Odense.

Figure 1. A circa 1890s slide by Povl Klavsen, a strew of diatoms from Cuxhaven, Germany. This source was among the items offered by Klavsen in an 1899 advertisement (Figure 6).


Figure 2. An 1893 advertisement from “The Observer”.


Figure 3. An 1894 advertisement, from “The Observer”.


Figure 4. Advertisement from “The Observer”, 1896.


Figure 5. From the German-language “Naturen”, 1897.


Figure 6. An 1889 advertisement from Povl Klavsen, listing the many sources of diatomaceous material that he had available. He offered to provide 100 select slides for $14.00 US. From “The American Monthly Microscopical Journal”.



The American Monthly Microscopical Journal (1890) Report of the Microscopical Society of San Francisco, “A donation of fossil diatomaceous deposits was received from P. Klavsen, Odense, Denmark, and with them a small quantity of recent diatoms from Odense Fjord”, Vol. 11, pages 217-218

The American Monthly Microscopical Journal (1899) Advertisement from Povl Klavsen, Vol. 20, pages 132-133

Bracegirdle, Brian (1998) Microscopical Mounts and Mounters, Quekett Microscopical Club, London, page 59 (note: misspelled as “Klaysen”)

Brandt, K., and C. Apstein (1908) “P. Klavsen, Odense, Dänemark (Hunderupvei 44) liefert gefärbte, in Styrax eingeschlossene Einzelpräparate von den folgenden Arten von Planktondiatomeen”, Nordisches Plankton, Vol. 19, page 140

Genealogical information on Povl Klavsen and family (accessed August, 2020) https://www.geni.com/people/Povl-Klavsen/6000000011251156307

Hansen, J.B. (1985) An Outline of Phycology in Denmark

Natural History Museum of Denmark, Algal Herbarium (accessed August, 2020) https://samlinger.snm.ku.dk/en/dry-and-wet-collections/botany/algal-herbarium

Naturen (1897) Advertisements from Povl Klavsen, Vol. 21

The Observer (1893) Advertisements from Povl Klavsen, Vol. 4

The Observer (1894) Advertisements from Povl Klavsen, Vol. 5

The Observer (1896) Advertisements from Povl Klavsen, Vol. 6

Rosenbauer, Karlheinz A. (2003) Mikroskopische Präparate, John Wiley and Sons, pages 155-157