Knud Jessen (29 November 1884 – 14 April 1971) was a Danish

botanist Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

and quaternary geologist.

Biography

Jessen was born at

Frederiksberg Frederiksberg () is a part of the Capital Region of Denmark. It is an independent municipality, Frederiksberg Municipality, separate from Copenhagen Municipality, but both are a part of the region of Copenhagen. It occupies an area of less tha ...

, Denmark. He was a student at the University of Copenhagen and was awarded cand.mag. in natural history and geography with botany as a major in 1911. He was state geologist 1917–1931. In 1931, he succeeded C.H. Ostenfeld as professor of

botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

at the

University of Copenhagen The University of Copenhagen (, KU) is a public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in Scandinavia, after Uppsala University. ...

and director of the

Copenhagen Botanical Garden The University of Copenhagen Botanical Garden (), usually referred to simply as Copenhagen Botanical Garden, is a botanical garden located in the centre of Copenhagen, Denmark. It covers an area of 10 hectares and is particularly noted for its ext ...

, a position he held until his retirement in 1955. His scientific works mainly concern vegetation history during the

Eemian interglacial The Last Interglacial, also known as the Eemian, was the interglacial period which began about 130,000 years ago at the end of the Penultimate Glacial Period and ended about 115,000 years ago at the beginning of the Last Glacial Period. It cor ...

, the late glacial period of the

Wisconsin glaciation The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated ...

and in the

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

investigated using

pollen analysis Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the mic ...

. Jessen had come into contact with the Irish naturalist

Robert Lloyd Praeger Robert Lloyd Praeger (25 August 1865 – 5 May 1953) was an Irish naturalist, writer and librarian. Biography Early life and education From a Unitarian background, he was born and raised in Holywood, County Down; he had four brothers and a ...

and made field-work on the

quaternary geology Quaternary geology is the branch of geology that study developments from 2.58 million years ago to the present. In particular, Quaternary geology study the process and deposits that developed during the Quaternary, a period characterized by Glacial ...

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

during 1934-1935. Together with his assistant, Frank Mitchell, he was able to describe both the post-

glacial A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

vegetation development of

and that of the

, with the presence in

of such plants as

Rhododendron ponticum ''Rhododendron ponticum'', called common rhododendron or pontic rhododendron, is a species of flowering plant in the ''Rhododendron'' genus of the heath family Ericaceae. It is native to the Iberian Peninsula in southwest Europe and the Caucasus ...

Abies alba Firs are evergreen coniferous trees belonging to the genus ''Abies'' () in the family Pinaceae. There are approximately 48–65 extant species, found on mountains throughout much of North and Central America, Eurasia, and North Africa. The g ...

, Erica scoparia and

Buxus sempervirens ''Buxus sempervirens'', the common box, European box, or boxwood, is a species of flowering plant in the genus ''Buxus'', native to western and southern Europe, northwest Africa, and southwest Asia, from southern England south to northern Morocco ...

. Jessen was acknowledged by honorary doctorates at the

University of Cambridge The University of Cambridge is a Public university, public collegiate university, collegiate research university in Cambridge, England. Founded in 1209, the University of Cambridge is the List of oldest universities in continuous operation, wo ...

and

University of Dublin The University of Dublin (), corporately named as The Chancellor, Doctors and Masters of the University of Dublin, is a research university located in Dublin, Republic of Ireland. It is the degree-awarding body for Trinity College Dublin, whi ...

. He was a member of the

Royal Danish Academy of Sciences and Letters The Royal Danish Academy of Sciences and Letters ({{Langx, da, Det Kongelige Danske Videnskabernes Selskab or ''Videnskabernes Selskab'') is a Danish academy of science. The Royal Danish Academy was established on 13 November 1742, and was create ...

and served on the board of directors of the

Carlsberg Foundation Carlsberg Foundation () is a not-for-profit organization that was founded by J. C. Jacobsen in 1876, by allocating some of his shares in the Carlsberg Brewery to fund and operate the Carlsberg Laboratory and the Museum of National History at ...

. Jessen also lived in the Botanical Gardens in his later life. He became a Knight in the

Order of the Dannebrog The Order of the Dannebrog () is a Denmark, Danish order of chivalry instituted in 1671 by Christian V of Denmark, Christian V. Until 1808, membership in the Order was limited to fifty members of noble or royal rank, who formed a single cla ...

in 1936 and Commander 2nd degree in 1949.

Personal life

Jessen married Ingrid Holm (1884-1984) and had four children, including Poul Holm Jessen, a chemist who founded and ran the plastics company Scandiflex.

Selected scientific works

*Jessen, K. (1920) Moseundersøgelser i det nordøstlige Sjælland. Med Bemærkninger om Træers og Buskes Indvandring og Vegetationens Historie (Bog investigations in Northeast

Zealand Zealand ( ) is the largest and most populous islands of Denmark, island in Denmark proper (thus excluding Greenland and Disko Island, which are larger in size) at 7,031 km2 (2715 sq. mi.). Zealand had a population of 2,319,705 on 1 Januar ...

with notes on the immigration of trees and shrubs and the development of the vegetation). Doctoral dissertation. Danmarks Geologiske Undersøgelse, II.række, 34, 1-243. * *Jessen, K. & V. Milthers (1928) Stratigraphical and palaeontological studies of interglacial fresh-water deposits in

Jutland Jutland (; , ''Jyske Halvø'' or ''Cimbriske Halvø''; , ''Kimbrische Halbinsel'' or ''Jütische Halbinsel'') is a peninsula of Northern Europe that forms the continental portion of Denmark and part of northern Germany (Schleswig-Holstein). It ...

and northwest

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. Danmarks Geologiske Undersøgelser II rk. Vol. 48: 1-379. *Jessen, K. with the assistance of H. Jonassen (1935) The composition of the forests in northern Europe in

Epipalaeolithic In archaeology, the Epipalaeolithic or Epipaleolithic (sometimes Epi-paleolithic etc.) is a period occurring between the Upper Paleolithic and Neolithic during the Stone Age. Mesolithic also falls between these two periods, and the two are someti ...

time. Biologiske Meddelelser, Kongelige Danske Videnskabernes Selskab 12 (1): 1-64. *Jessen, K. (1949) Studies in Late

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

deposits and flora-history of

. Proceedings of the Royal Irish Academy 52, sect. B, no. 6: 85-290.

References

{{DEFAULTSORT:Jessen, Knud 20th-century Danish botanists 20th-century Danish geologists Danish science writers Academic staff of the University of Copenhagen University of Copenhagen alumni Palynologists 1971 deaths 1884 births Commanders Second Class of the Order of the Dannebrog Members of the Royal Swedish Academy of Sciences