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

botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...

and quaternary geologist.

Biography

Jessen was born at

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

, Denmark. He was a student at the

University of Copenhagen The University of Copenhagen ( da, Københavns Universitet, 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 ...

and was awarded

cand.mag. Candidatus magisterii (male), or candidata magisterii (female), abbreviated as cand.mag., is an academic degree currently awarded in Denmark. The degree is officially translated into English as Master of Arts and currently requires 5 years of studi ...

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 biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

at the

University of Copenhagen The University of Copenhagen ( da, Københavns Universitet, KU) is a prestigious public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in ...

and director of the

Copenhagen Botanical Garden The University of Copenhagen Botanical Garden ( da, Botanisk have), 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 ...

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

Eemian interglacial The Eemian (also called the last interglacial, Sangamonian Stage, Ipswichian, Mikulin, Kaydaky, penultimate,NOAA - Penultimate Interglacial Period http://www.ncdc.noaa.gov/global-warming/penultimate-interglacial-period Valdivia or Riss-Würm) wa ...

, the

late glacial The Late Glacial Interstadial (LGI) c. 14,670 to c. 12,890 BP, also called the Bølling–Allerød interstadial, represents the first ''pronounced'' warming since the end of the Last Glacial Maximum (LGM). Human populations, which had previous ...

period of the

Wisconsin glaciation The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cor ...

and in the

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

investigated using

pollen analysis Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and ''-logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposits ...

. Jessen had come into contact with the

Irish Irish may refer to: Common meanings * Someone or something of, from, or related to: ** Ireland, an island situated off the north-western coast of continental Europe ***Éire, Irish language name for the isle ** Northern Ireland, a constituent unit ...

naturalist

Robert Lloyd Praeger Robert Lloyd Praeger (25 August 1865 – 5 May 1953) was an Irish naturalist, writer and librarian. Biography From a Unitarian background, he was born and raised in Holywood, County Down. He attended the school of the Reverend McAlister and t ...

and made field-work on the

quaternary geology Quaternary geology is the branch of geology that study developments from 2.6 million years ago onwards. In particular, Quaternary geology study the process and deposits that developed during the Quaternary, a period characterized by glacial-intergl ...

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

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

glacial A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...

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 ''Rhododendron'' native to the Iberian Peninsula in southwest Europe and the Caucasus region in northern West Asia. Description ''R. ponticum'' is a d ...

Abies alba ''Abies alba'', the European silver fir or silver fir, is a fir native to the mountains of Europe, from the Pyrenees north to Normandy, east to the Alps and the Carpathians, Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Serbia, and sou ...

Erica scoparia ''Erica scoparia'', the green heather, is a shrubby species of heath in the flowering plant family Ericaceae. It is native to the western Mediterranean Basin in the Iberian Peninsula (Spain and Portugal), Northwest Africa (Morocco, Algeria and Tu ...

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 , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

and

University of Dublin The University of Dublin ( ga, Ollscoil Átha Cliath), corporately designated the Chancellor, Doctors and Masters of the University of Dublin, is a university located in Dublin, Ireland. It is the degree-awarding body for Trinity College Dubl ...

. He was a member of the

Royal Danish Academy of Sciences and Letters {{Infobox organization , name = The Royal Danish Academy of Sciences and Letters , full_name = , native_name = Det Kongelige Danske Videnskabernes Selskab , native_name_lang = , logo = Royal ...

and served on the board of directors of the

Carlsberg Foundation Carlsberg Foundation ( da, Carlsbergfondet) 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 Frederiksborg Palace. ...

. 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 ( da, Dannebrogordenen) is a Danish order of chivalry instituted in 1671 by Christian V. Until 1808, membership in the order was limited to fifty members of noble or royal rank, who formed a single class known a ...

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 ( da, Sjælland ) at 7,031 km2 is the largest and most populous island in Denmark proper (thus excluding Greenland and Disko Island, which are larger in size). Zealand had a population of 2,319,705 on 1 January 2020. It is the 1 ...

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 ( da, Jylland ; german: Jütland ; ang, Ēota land ), known anciently as the Cimbric or Cimbrian Peninsula ( la, Cimbricus Chersonesus; da, den Kimbriske Halvø, links=no or ; german: Kimbrische Halbinsel, links=no), is a peninsula of ...

and northwest

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

. 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 {{Infobox organization , name = The Royal Danish Academy of Sciences and Letters , full_name = , native_name = Det Kongelige Danske Videnskabernes Selskab , native_name_lang = , logo = Royal ...

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). It follows the Neogene Period and spans from 2.58 million years ...

deposits and flora-history of

Proceedings of the Royal Irish Academy The ''Proceedings of the Royal Irish Academy'' (''PRIA'') is the journal of the Royal Irish Academy, founded in 1785 to promote the study of science, polite literature, and antiquities Antiquities are objects from antiquity, especially the ...

52, sect. B, no. 6: 85-290.

References

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