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Johannes Iversen Dec. 27th 1904 - Oct. 17th 1971 D. g. F. 24 114 Johannes Iversen Johannes Iversen died on October 17th, 1971. he was engaged as an assistant at the Sav­ Within the disciplines of plant ecology and of ings Bank at Sønderborg and after a com­ the history of vegetation his life's work stands paratively short time he was made a director. out as one of the most original, inspired and Iversen went to a German school until, in penetrating. - Unfortunately he did not live 1920, due to the Genforening (the reunion to finish his work on the vegetational history of North Slesvig with Denmark in 1920) he and ecology of Draved Forest, a work to which was sent to a Danish high school. As a con­ he had devoted the last 20 years. More par­ sequence he was a master at the German ticularly it was the lime forest to which he language and up to 1940 he wrote all his ar­ gave his attention. Few have delighted like ticles in this language. After that date he wrote him in the beauty of the linden tree and in in English and made a great effort to master my memory the man and the tree are mys­ the language. teriously connected. He finished _ school in Sønderborg State The lime prefers fertile soil, yet may, while School in 1923 and took his degree as a still a young tree bend like an humble vine Bachelor of Botany in 1930 at the University enduring deep shadow. If brought out into of Copenhagen. Ostenfeld became his teacher, light, however, it shoots up fast, tall and but Raunkiær - then still active - was the straight spreading its branches harmoniously to one whose influence was to mark his work. all sides. The bark remains smooth and even, When, in 1931, Knud Jessen left The Geo­ and beneath the surface run the long, strong logical Survey of Denmark in order to become and sinewy bast fibres. The foliage stays fresh Professor of Botany, Iversen was appointed to and green far into the summer when other the job of part time assistant at this institute. trees have turned dark or faded. In the his­ In 1932 he participated in Aage Roussell's ex­ tory of vegetation the lime replaces the oak pedition to Godthaabsfjord in Greenland and and during the atlantic period it creates the in the autumn of 1933, together with Knut selfperpetuating climax forest. It affords much Fægri amongst others, he took part in the Bal­ shade and only few trees will grow underneath tic course of pollen analysis under the guid­ it. It blossoms in the height of summer and ance of Lennart v. Post. Those six months its strong scent of honey, which attracts many were of decisive importance to him. He ac­ bees, is quite intoxicating. It stands with its quired a thorough knowledge of Quaternary roots deep in the sound and fertile mineral geology and pollen analysis as it was studied soil. in those days. For him the companionship of The beauty of the linden has been praised v. Post and Sernander, who was, in spite of since time immemorial. It was a sacred tree. being old, still full of intellectual vitality, was In heraldry its heartshaped leaves symbolize to become a lasting source of inspiration. the free landowner and its soft, yet stringy Not until 1938, having published his thesis wood which does not crack - white in colour in 1936, did he become afdelingsgeolog (sec­ but tinged with gold - was the favourite ma­ tional geologist) at the age of 34. He had to terial of the sculptors of the Middle Ages for cover personally all thie expenses involved in carving religious statues and altars, hence the printing his thesis and it took several years name — Lignum Sanctum. before he was free of debts. In 1942 he be­ came a State Geologist - an appointment he Iversen was born in 1904 at Sønderborg. Both kept until his death. In 1955 he was made lec­ his father Hans Iversen and his mother, née turer at the University of Copenhagen in pollen Asmussen, came of peasant stock from the analysis and Quaternary vegetational history. southeastern part of Jutland. As a young man In 1939, he married Miss Aase Thorlacius- his father was attached to "Brødremenighe­ Ussing, a daughter of the principal of a Sec­ den" (the Moravian Brethren) as a missionary. ondary School, Rev. B. Thorlacius-Ussing (who The family was deeply religious and marked died in 1955) and his wife Martha, née Ras­ by the close to earth type of devotion char­ mussen. The marriage was blessed with one acteristic of the Moravian Brethren. By chance daughter. Iversen had the great sorrow of Bulletin of the Geological Society of Denmark, vol. 24 1975 115 losing his wife half a year before his own and admired him, but the proposal was an ex­ death from heart failure. pression of exactly the opposite method to the In 1953 he was made a member of the one he himself wanted to employ, that is the Danish Academy of Science, where he was a study of the mutual competition among plants frequent visitor. His honours were few, but in face of a few decisive external influences choice: He was a Doctor Honoris Causa at - research that had to be carried out in na­ Uppsala and at Cambridge. ture. He accomplished this method in his thesis: Iversen's life work has its starting point in the "Biologische Pflanzentypen als Hilfsmittel in ecology of the plants: that is their relations der Vegetationsforschung", 1936, which was to soil, climate, light or shade and their mutual to be his only more extensive piece of writing competition. He had a profound knowledge of - some 220 pages. Only few besides him have the plants and their habitats having studied managed to create a similar total image. The them since childhood. As a consequence he framework is universal, that is the morpho­ was able in his research quickly to reach de­ logical adaptation of plants to drought or hu­ finite conclusions. His method reminds one of midity in the widest sense, the 'hydrotypes' that of Miss Marple's in the detective stories with the extremes Terriphytes-Limnophytes. by Agathe Christie. Miss Marple lives alone Of these groups the first one is divided into in a small house in a far away village and a series covering the Xerophytes-Hygrophytes. she possesses an intimate knowledge of the The classification of these eco-types is based inhabitants, more specifically their psychology on clearly visible morphological characteris­ and character. In the solution of a crime riddle tics and extensive statistical information dem­ Scotland Yard is very useful checking up on onstrates the justification of this classification. alibis and carrying out systematic investiga­ Also the distribution of plants in relation to tions, - yet when it comes to supplying the the humidity of the soil (the Hygrobic-types) final clue to the mystery they are unsuccess­ and the salinity of the place of growth (the ful. It is up to Miss Marple and with ease Halobic-types) was proved. The main part of and in great style she solves the problem, the research materials was collected at Skal- thanks to her profound knowledge of the ling, where Iversen profited from the work­ people involved. ing conditions created here by Niels Nielsen. At 24 while still a student Iversen pub­ Twice' Iversen went to Greenland in the lished a well-balanced and important study: summer - on both occasions to the farther "Studien iiber die pH-Verhaltnisse dånischer end of the Godthaabsfjord and in connection Gewasser und ihren Einfluss auf die Hydro- with the Norse investigations carried out by phyten-Vegetation." In this surprisingly mature the National Museum. The first expedition, piece of work he was able to prove how the • in 1932, formed the basis of two exceptional distribution of various hydrophytes is condi­ studies. tioned by the pH of the lakes. In "Moorgeologische Untersuchungen auf Peter Boysen Jensen, the Professor of Gronland" (1934) Iversen shows how the ar­ Plant Physiology had noticed the quiet and ta­ rival of the Norsemen to the area makes itself lented student - he may have felt himself known by the appearance of a widespread lay­ instinctively attracted by his congenial men­ er of charcoal which indicates that the vegeta­ tality. tion has been burnt down, for the purpose of While it was Raunkiær's idea to study the encouraging the growth of grass. Yet even ways of life of the plants in relation to a few more important was the fact that he could decisive outside factors, Boysen Jensen was of prove that a widespread layer of pupae of the the opinion that one ought to examine the re­ butterfly Agrotis occulta occurs precisely at actions of one single plant to all external in­ the level, which marks the end of the Norse fluences in the laboratory. In fact he proposed period in the Vestbygd. Precisely that same to Iversen a research programme along these summer the vegetation at the farther end of lines. Iversen was very fond of Boysen Jensen the Godthaabsfjord was lain waste by an ex- 8* 116 Johannes Iversen tensive attack of catarpillars (also Agrotis ocul- ical discussion frequently based on conjectures. ta) and for Iversen it was easy to imagine By publishing material based on the history that the attack by caterpillars at the end of of vegetation, Iversen was on solid ground the Norse period might have been a contri- and was able to draw reliable conclusions.

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