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. butary cause to the disappearance of the The result showed that only the most hardy Norsemen as their live-stock would have been plants have been able to survive on the nuna­ deprived of food. taks, whereas the more demanding plants in In 1937 he published an article barely four terms of temperature are later immigrants. pages long: "Et botanisk Vidne om Nordbo­ ernes Vinlandsrejser" ("Botanical Evidence of It was Knud Jessen who through his extensive the Vinland-journeys of the Norsemen"). The studies had laid the foundation for a division point of departure was his find of one small, of the post glacial into periods based on the delicate Iridaceae species with blue flowers Danish vegetational history and who estab­ (Sisyrhynchium angustifolium) quite close to a lished the very useful pollen zone boundaries. Norse ruin at the farther end of Godthaabs- It is to Iversen's merit that he penetrated deep­ fjord. In 1937 the number of finds had in­ ly into the working of the historical evolution creased to four in all - all of them close to of vegetation. He started with the late-glacial Norse ruins. Outside Greenland the nearest period where he could profit from his ex­ habitat of the plant is Newfoundland, 1700 periences in Greenland. km further south. Iversen refused the possibility Already in 1934 he made the decisive step of the Sisyrhynchium surviving the last glacial of introducing grasses and sedges into late- age on nunataks in Greenland. Its enigmatic glacial pollen diagrams which according to and isolated appearance in Greenland can, in the traditional practice was estimated on the his opinion, only be reasonably explained if basis of the sum of tree pollen, on the as­ one assumes that the Norsemen often obtained sumption that these were bound to represent hay in Vinland (close to the bay of Saint Law­ an essential part of the vegetation cover at rence) and that its seeds were being carried the time. Later, in 1936, he took the full con­ in this way to the Norsemen's settlements. sequences and included the grasses and sedges When, in 1937, Iversen returned to the in­ in the pollen sum. most part of the Godthaabsfjord it was his In the mid-thirties some scholars were of intention to try to clarify its history of vege­ the opinion that the late-glacial period had tation through pollen analytical examinations been considerably warmer than had hitherto of the lake gyttja. In order to be able to inter­ been assumed. The proof was supposed to be pret the pollen diagrams correctly, however, the numerous examples of pollen of trees statistical examination of the contemporary and bushes such as alder, oak, lime and hazel. plants had necessarily to be related to the Iversen compared these finds with the other present production of pollen. Not until 1954 known finds of plants from the period and were the results published. The botanical ma­ concluded that the theory must be erroneous. terial was presented in a paper: "Ober die The problem was how to find the source of Korrelationen zwischen den Pflanzenarten in error. How did those incompatible plant finds einem gronlandischen Talgebiet" whereas the happen to be placed side by side in the layers? part dealing with the history of vegetation As the late-glacial lake-deposits to a very large was published seperately as "Origin of the Flo­ extent consist of clay which has been washed ra of western Greenland in the Light of Pollen down from the boulder clay surrounding the Analysis". The latter, especially, is of decisive lakes, it is conceivable that also the pollen importance. For more than 50 years botanists, from the warmth-requiring trees came from zoologists and others had been discussing the that same source that is in the last instance question of the extent to which plants and from interglacial or more ancient bogs. - Pol­ animals might have been able to survive the len-analytical examinations of the boulder last-glacial, period on the mountaintops (nuna­ clay proved the idea to be right. Iversen, how­ taks) surrounded by the inland ice — a theoret­ ever, did not leave it at that. He worked out Bulletin of the Geological Society of Denmark, vol. 24 1975 117

a method of separating the secondary pollen Most of the Danish kitchen middens were from the primary pollen which was contem­ linked with the highest water level of the porary with the sediments. By doing this, in Littorina sea, and the latest and highest of the 1936, in a masterly fashion, he succeeded in two Littorina transgressions in Sweden could making the clay sediments, especially the late- be seen to have culminated simultaneously glacial ones, available for pollen analysis. - In with the early period of passage graves, with the years to come fundamental results followed the consequence that the major part of the one another in rapid succession. The disen­ Danish kitchen middens must have dated from tanglement of the much discussed sequence of the same period - provided that one could layers at Nørre Lyngby and the dating of the point to more than one Danish transgression famous "Lyngby-Arrowhead" were published and that the last was the highest and con­ in, 1942 and in that article, proof is presented temporary with the last Swedish transgression. of a warmer interval in the late-glacial per­ The Danes, however, insisted that Denmark iod prior to the Allerød period, i. e. the Bøl­ only had one single transgression and that it ling period. In 1944, 1947 and 1951 respec­ culminated during the late Mesolithic. tively, information was published of finds of Iversen was very fond of the writings of the Oland Rock-rose, Blue Cornflower and the Søren Kierkegaard and it might have been the steppe-plant Ephedra in late-glacial sediments. reading of the introduction to the passage In 1953 the Allerød period, the warmer cli­ "Guilty or not guilty" at the end of his book matic interval in the late-glacial period, was "Studier på Livets Vej" ("Stages on Life's dated thanks to the method of Carbon-14; this Way"), where the lake of Søborg plays an es­ was one of the first tasks of the newly es­ sential part, that made him choose the now tablished dating laboratory at Copenhagen. dried out Søborg Lake as the most suitable for In 1954, Iversen gathered together his late- solving the problem of one or more Littorina glacial studies in an exceptionally handsome transgressions. During the Littorina period the and, brilliant treatise in a volume dedicated lake was an inlet which joined the sea through to Knud Jessen. - Whereas the earlier histor­ a long narrow valley, a threshold, which was ical studies of vegetation had to be based on then below sea-level. If there had been several leaves, twigs, seeds, fruits and suchlike plainly transgressions and regressions of the water sur­ visible remains of plants, it was now possible face of the Littorina sea one might have ex­ for Iversen - thanks to his thorough studies of pected the gyttja deposits in the former Lake pollen morphology - to include a large number Søborg to show several inlet periods (trans­ of newly discovered species in his list of plants gressions) interchanging with lake periods (re­ from the late-glacial period. On the basis of gressions). Through corings in the lake depos­ this unique material he accomplished a divi­ its and analysis of the occurring salt- and sion of the vegetational development within freshwater diatoms, Iversen was able to in­ the period giving a precise account of changes dicate four inlet periods or transgressions in climate. His evidence for summer and win­ that thanks to pollen analysis could be dated ter temperatures as well as the precipitation in relation to the vegetational history so that was born out by these plant records. the three earliest occur within the Atlantic pe­ In between his studies of ecology and vege­ riod and the latest and presumably the high­ tational history, Iversen also dealt with other est at the beginning of the Sub-boreal period. subjects. Thanks to his talent for singling out - Other scholars have in different ways con­ the essential in any problem he often succeeded tributed to the elucidation of problems re­ surprisingly quickly in reaching unerring solu­ lated to the Littorina' transgressions, yet the tions. I would like to illustrate this with two contribution made by Iversen in 1937 will, examples. beyond any doubt, remain the classical solution In 1928, Otto Rydbeck, the Swedish ar­ of the problem. chaeologist had suggested that the Danish kit­ In 1938 Iversen was engaged in the exam­ chen middens, were contemporary with the ination of certain pollen for the purpose of dolmens and passage graves of the Neolithic. being able to identify the plants in geological 118 Johannes Iversen deposits. During this work he noted that thrift, VIII (Atlantic Sub-Boreal period) at the Armeria vulgaris, had two quite different point where the oak forest and especially the forms of pollen (A and B respectively) which lime was in fast decline. While Knud Jessen never appeared together on one plant. Cul­ left the question open as to the reason for tivation experiments showed that plants of the this, others interpreted the decline of the oak A-pollen type could only be pollinated by the forest as the result of a climatic deterioration. B-pollen and vice versa. Iversen now went to — Towards the end of the thirties pollen grains examine the pollen of the genus Armeria from of the various plantains had been successfully Northern Greenland and Northern Norway classified. Furthermore they had been traced (A. labradorica), which, as it turned out, did in postglacial deposits. In this way it was dis­ not have different pollen (dimorphism), but covered that the ribwort plantain only appears only one form (monomorphism), which was after the zone boundary VII-VIII and often in an intermediate form between the A and the large numbers - but never earlier. It was, as B-types, yet closer to the A form. Experiments a consequence, plain to Iversen that the with pollination showed that the self-pollinat­ change in composition of the forest trees was ing Armeria labradorica with monomorphic caused by cultivation, through the interfer­ pollen could pollinate the B-type of Armeria ence of man who cleared the forest. To him vulgaris, but not the A-type. - The conclu­ it was inconceivable that ribwort plantain sion was that A. labradorica originated'from should be able to survive in a primeval forest. the A-type. After an examination of thrift pol­ To this must be added, it was pointed out at len from a long series of localities scattered the same time that the introduction into Den­ over the northern hemisphere it turned out mark of Neolithic agricultural methods of that all the habitats of the dimorphic Armeria farming probably happened at roughly that vulgaris occur within the - 10° January iso­ same period. As a consequence, Iversen could therm while all the monomorphic appear in offer a brilliantly clear and acute account of colder areas. Furthermore it turned out that the changes that took place in the forest as while A. vulgaris (with dimorphism and in­ expressed in the pollen diagrams immediately sect-pollination) showed rather great morpho­ above the zone boundary VII-VIII. - Large logic variation, the monomorphic thrift var­ areas of forest had been cut down and ieties (with self-pollination) could be subdivid­ burnt, cereals had been sown in the ashes ed in a number of morphologically stable and later the scorched expanses had been left groups: A. macloviana, A. scabra, A. chilensis as commons until they again became forest and so on, with subgroups. Iversen considered and the earlier condition was reestablished. the dimorphic A. vulgaris as the primeval One of the proofs of burning was the pre­ form, and the monomorphic species as hav­ dominance of birch trees that invaded the ing arisen from this one during extreme arctic burnt areas where their tiny seeds had fa­ conditions, presumably during the Ice Age. vourable germination conditions. The pollen The treatise was published in the 'Biologiske diagrammatic decline of the oak forest was fic­ Meddelelser', published by the Academy of titious up to a point as its curve was effected Science in 1940 as, "Blutenbiologische Stu­ by the immigration of birch, elder and willow dien I". The title shows that Iversen had hoped in the cleared areas. Finds of pollen of cul­ for an opportunity of continuing these studies. tivated grain indicated agriculture and the Alas, there never was a follow up to this slightly later appearance of ribwort plantain splendid piece of research. in large number together with the high per­ centage of grasses and wormwood show the temporary existence of large pastures. In 1941 Iversen marked his return to palaeo- ecology with the, by now, classical treatise, This interpretation was so unexpected and "Landnam in Denmark's Stone Age". This elegant that in the first place it produced strong was a work which was to inspire a whole gen­ criticism. It was therefore decided to re-enact eration of vegetation historians. — Knud Jes­ the "Landnam" as an experiment. It took 10 sen had fixed his pollen zone boundary VII- years before the plan could be carried out at Bulletin of the Geological Society of Denmark, vol. 24 1975 119

the research area at Draved forest which had perature decreased in the positive direction been established thanks to large subsidies from (towards the east!). Iversen was distinctly vi­ the Carlsberg Foundation. During the period sual in his approach, and by making his sys­ 1951-54 a considerable portion of the forest tem of co-ordinates function like a map of was cleared with the sole aid of polished thin- Europe he made it quite obvious that the butted flint axes, burnt and some minor areas summers became warmer, when one was mov­ sown. Later, half of the cleared ground was ing towards the south and the winters colder grazed for a number of years whereafter, left when one went eastwards. By plotting the to itself, it became overgrown. Before the start combined summer and winter temperatures of of the experiment the area was mapped out various meteorological stations into the system including the trees and the vegetation of herbs of coordinates and by indicating whether or and with short intervals this practice has been not the plant in question was flowering near continued. Now, 20 years later, it can be the station, he obtained a clear expression of stated with certainty that all conditions ob­ the growth possibilities of the species and he served during and after the experiment have was able to isolate its thermosphere. It now confirmed Iversen's interpretation of the pol­ transpired that each of the three species in len diagrams. question had specific demands. The Mistletoe generally demands a high temperature in sum­ The winters of 1939 and 1942 were excep­ mer (min. 16°C), but will on the other tionally cold and a large number of plant hand tolerate severe cold (max. - 8°C). Ivy, on species either suffered severe frost damage or the contrary, does not stand up to winters died outright. Especially evergreens such as ivy below - 1.5" as a mean temperature for Jan­ and holly suffered badly, while another ever­ uary, but will survive cool summers (about green, the mistletoe evidently did not mind 14°C). The demands of holly are not unlike the cold. Iversen made a thorough survey of those of ivy only more extreme, it will tolerate the damages in Denmark. During the period only -0.5° in January, but will make do with from the Ice Age and until to-day one can about 13°C in summer. On the basis of a point to a rise, a culmination (some 5.000 very extensive pollen analytical material Iver­ years ago) and a decrease in summer tem­ sen was now able to illustrate the change in peratures. The appearance and disappearance summer and winter temperatures from Atlantic of the pond tortoise and the aquatic water- to Subboreal and further on to the Sub-atlantic chestnut are classic examples of this. On the period. - The paper appeared in a volume other hand there has been no possibility of dedicated to Lennart von Post on the occasion evaluating the winter temperature. Iversen was of his 60th birthday in 1944 and was a suit­ keenly interested in this question and he want­ able homage to the founder of the pollen ed precise results. This presupposed the pos­ statistic method. sibility of defining .the thermosphere of the chosen climatic indicators: mistletoe, ivy and In 1960 Iversen had been studying the forest holly. The concept of the thermosphere of a ecologic problems at Draved forest for more plant was defined by the naturalist J. F. than 10 years, a sufficient span of time for Schouw as early as 1822, as the sum of the obtaining an insight into the essential prob­ conditions of temperature subject to which a lems, but too brief to allow an unambiguous plant is able to thrive in nature. It soon turned interpretation of the minor changes in the out that the distribution of the above-men­ forest. The life of a forest is long compared tioned 'plants followed neither the summer to that of man. Yet his intimate knowledge of nor the winter isotherms. Iversen then con­ the post-glacial vegetation history supplied structed a system of co-ordinates with the him with a historical perspective which en­ July temperature as ordinate and the January abled him to place his observations of the liv­ temperature as abscissa so that the summer ing forest in a larger context. In the preface temperature increased in the negative direc­ to his paper: "Problems of the Early Post- tion (towards the south!) and the winter tem­ Glacial Forest Development in Denmark" Bulletin of the Geological Society of Denmark, vol. 24 1975 121

describe the period from the melting of the The mastery of Iversen most clearly emerges ice until the present time. It was a happy in the brief treatise. - The subject is presented choice. In about one hundred pages, he suc­ in a lucid and well arranged manner, the ceeded in summarizing the extensive and argument is brief, precise and comprehensive comprehensive knowledge of this period - - like a piece of sculpture nothing can be largely the results of his own studies, some of added nor subtracted without disrupting the them as yet unpublished - in an inspired de­ harmony of its entirety. The language is alive scription for which the learned as well as the and clear, in spite of the fact that it was the layman are indebted to him. result of endless toil. Iversen wrote in pencil It has previously been mentioned that Iver- in order better to be able to erase. I remem­ sen's epoch-making achievement within his ber our collaboration on pollen morphologic chosen field was due to his profound knowl­ definitions and types. The work lasted for some edge of plants and their ecology. A prere­ five to six years. Besides preliminary sketches quisite of the application of this knowledge to the final draft of the article was typed out fossil material was, however, that it be pos­ more than twenty times. Having arrived at the sible - to classify macro- and microfossils to twentythird fair copy Iversen decided that fur­ genera and species. From about the middle of ther minor errors might be corrected in proof. the nineteen thirties to the mid-fifties, a pio­ I shall never forget the expression of Hilmar neer work was being carried out in Denmark Ødum, the then director of The Geological with the purpose of making it possible to Survey of Denmark, when telling us that we define those observations of pollen (the pol­ had by now had seven lots of proofs and len-morphologic units) that might serve as a that the eighth would positively have to be foundation for the identification of pollen of the last. The treatise consisted of only twenty different plants. Iversen was the head of the small pages of print. The pleasure of reading Bog Laboratory at The Geological Survey of Iversen's papers is like that of listening to 18th Denmark and together with collaborators part­ century music. In the same way as the leitmo­ ly at this institute and partly at the newly tif in a fugue by Bach has subordinated figures established Bog Laboratory at the National Mu­ that sound together as well as in unison with seum, this most intensive and fruitful research the leitmotifs, so are works by Iversen sa­ work was carried out resulting in a long turated with patterns of observations and series of reliable identifications of the species thoughts that make it possible to return con- of fossil pollen. - In 1950 the treatise: "Pol­ tinously to them in search of fresh knowledge lenmorfologiske definitioner og typer" ("Pol- ' and inspiration in tune with one's own more lenmorphologic Definitions and Types") was profound penetration into the theme. published in collaboration with the present Mention has been made above of only a few writer and in the same year appeared: "Text especially significant works. Iversen was, how­ Book of Modern Pollen Analysis", written in ever extremely hard-working and he wrote collaboration with Knut Fægri, Professor at about ninety papers. Only six of these amount Bergen. The Text Book is a competent and to more than thirty pages and only his thesis concise treatment of all the aspects of pollen for the doctorate attained 220 pages. The bulk analysis including keys to pollen-determinations, of his work is brief communications, printed sampling, unconsolidated sediments, the draw­ lectures of preliminary information - yet all ing of diagrams, statistics, how to interpret of them essential. As a rule he published an the material and last, but not least, the men­ adequate part of the material on which his tioning of a long series of possible misinter­ observations had been based, yet it was in pretations that the pollen analyst must neces­ rare cases such as for instance in his thesis, in sarily come across. The book has been worn the Landnam-paper and in his late-glacial to tatters by an entire generation of pollen studies, that he produced the entire extensive analysts and in 1964 a new revised edition ap­ and carefully collected material, which was peared. always the solid basis of his conclusions. As a lecturer Iversen was uneven. He was 122 Johannes Iversen at his best when he lectured from a manu­ pathetic. The matter that at any given moment script, which had been finished in time - and was in focus was all important and drove when he stuck to it. The crucial point was the everything else out of his vision. His absent- explanation of the first slide, which forced him mindedness, that twinbrother of concentration, to take his eyes off the solid ground offered must undoubtedly be seen as a consequence of by the manuscript with the not unusual result this. All those who have known him will be that he strayed away from the carefully worked able to tell most stunning tales of this absent- out lecture - or he came to a full stop be­ mindedness. cause the slide had set in motion entirely new Iversen as a rule avoided getting involved ideas. On returning to the manuscript as a rule with administration. On the other hand he did he found the right place - yet this was not a great and conscientious job when, occasion­ always the case. ally, he did take it on. His work as a member, Iversen's was a markedly dialectic mind and from 1959-67, of 'Statens almindelige Vi- to approach a problem from continuously denskabsfond' bears witness to this, as does the changing angles was for him an indispensable organisation of the Quarternary Botanical Con­ part of the process of knowledge proper. With gress in Denmark in 1953. A place apart should frequently a quite astounding stubbornness he be given to the work he did in order to secure would go on producing arguments in favour the research areas of Draved Forest, Skal­ of a special point of view, whereupon he most lingen and Løvenholm forest. He was here unexpectedly would view the matter under an fighting for vital research interests and it was entirely new angle. In order to carry on a dis­ thanks to his initiative that the 'Komitéen for cussion with him it was necessary to know both Forskningsarealer' was established in 1968 un- • him and the theme well. Very often he said der the auspices of the Academy of Science. the opposite of what he ment, jumping with­ Iversen was an all-round naturalist and it out warning to and fro within the subject. was a treat to accompany him whether at For him, discussion was never a play with Skallingen, in Greenland or in Draved forest. arguments, but a deeply serious matter which When with him nature opened up. In my me­ allowed no time to be wasted on less care­ mory the experience of the singing of birds, fully prepared contributions — they were swept the form of leaves and the sharp charac­ aside - pleasantly as a rule yet with deadly teristic smell of mor-ground stand out with a poignancy, which, however, was not always strange intensity when experienced in his com­ understood. - To carry out a debate with pany because of the way in which he seemed Iversen was, as a rule, so inspiring and en­ to communicate his own love of nature to his riching that one forgot time and place. I re­ companion. Some are blessed with a talent call, how discussions started during a small that make others remember their words. Iver­ stroll at Draved forest after supper, would be sen made one remember what one saw. He continued, while still wandering, until the light was, also very well versed in literature and of dawn when the grass was drenched with philosophy. Names like Sigrid Undset, Albert dew. Schweitzer, Dostojefski, Karl Barth, Simone Equally characteristic of Iversen was his Weil and Pierre Teilhard de Chardin may give singleness of purpose and his unusual ca­ an idea of his many interests. Poul Martin pacity for concentration. His contribution to Møller and Søren Kierkegaard ('the Acts of research bears witness of this. At times, how­ Love') were presumably the two authors to ever, during daily contacts this singleness of whom he most frequently returned. During a purpose might take a shape which could be period, while young, he had a certain con­ mistaken for ruthless egoism. Yet to him it nection with a religious movement, the Tide- was the cause, the work and the problems hvervsbevægelse, inspired by Karl Barth. that were of paramount importance and a Iversen was slightly above average in height, different interpretation would presumably have harmoniously built with a calm, quiet and been impossible to his way of thinking. Per­ rather reticent manner which did not prevent sonally he was extremely considerate and sym­ him from being a live and sharp observer of Bulletin of the Geological Society of Denmark, vol. 24 1975 123

the surroundings yet which helped to conceal 1934: Fund af Vildhest (Equus caballus) fra over­ gangen mellem sen- og postglacialtid i Dan­ a sensitive and impressionable disposition. The mark. Danmarks geol. Unders. (4) 2, (13), cords of his heart were tightened to breaking 16 pp. (Also in Meddr dansk geol. Foren. 8, point hence its pure and clear notes. 327-340). 1934: Studier over vegetationen i Ringkøbing fjord All through life he was favoured with good før Hvide Sande-kanalens genåbning 1931. In working conditions, though he had to wait long A. C. Johansen og H. Blegvad (Eds): Ringkø­ before obtaining reasonable economic condi­ bing fjords naturhistorie i brakvandsperioden 1915-31. tions. 1934: Moorgeologische Untersuchungen auf Gron- Plant ecology was the nucleus of his re­ land. Ein Beitrag zur Beleuchtung der Ursachen des Unterganges der mittelalterlichen Nordman- search and from that mainstream it spread in nerkultur. (Vorlaufige Mitteilung). Meddr. dansk all directions. geol. Foren. 8, 341-358. Iversen went his own way. Within his chosen 1935: Nordboernes undergang på Grønland i geolo­ gisk belysning. Grønl. Selsk. Årsskr. 1934-35, field his skill was supreme to such a degree 5-18. that only few could follow him. He did not 1936: Biologische Pflanzentypen als Hilfsmittel in der found a school and left no pupils proper - Vegetationsforschung. Ein Beitrag zur okologi- schen Charakterisierung und Anordnung der yet to many scholars his writings and conver­ Pflanzengesellschaften. Meddr Skalling-lab. 4, sations have meant decisive and life-long in­ 224 pp. Also, København: Levin & Munks­ gaard. spiration. 1936: Selvbiografi. Københavns Univ. Festskrift, Nov., He preferred nature to the laboratory and 185-186. at Draved forest he became part of the fauna, 1936: Sekundares Pollen als Fehlerquelle. Eine Kor- rektionsmethode zur Pollenanalyse minerogener listening and observing. He reluctantly picked Sedimente. Danmarks geol. Unders. (4) 2, (15), a flower, but preferred with his beautiful hands 24 pp. gently to disentangle it from its surround­ 1937: Nordslesvigs planteverden. Min Hjemstavn 10, 19-31. ings in order better to observe it. 1937: Undersøgelser over Iitorinatransgressioner i Iversen's attitude to research can only pro­ Danmark. Meddr dansk geol. Foren. 9, 223- 232. perly be understood if seen in the light of his 1937: Nye undersøgelser over litorina-transgressioner- deeply religious total view of existence. He ne i Danmark. (Autorref.) Naturh. Tid. 1, 42. felt that to explore life in all its forms was 1938: Sekundare Pollen als Fehlerquelle. Verh. III. Int. Quartar-Konf., Wien Sept. 1936, 2, 225- his mission in life, a vocation which he ap­ 228. proached with loving humility. From this at­ 1938: Pollenanalytiske tidsbestemmelser af midtjyske mesolitiske bopladser. In Th. Mathiassen: Gu- titude springs the strength which sustained his denaa-kulturen. En mesolitisk indlandsbebyggel- life-work and gave it lasting value. se i Jylland. Aarb. nord. Oldk. Hist. 1937, Let us pay tribute to his memory! 182-186. 1938: Et botanisk vidne om nordboernes Vinlands- /. Troels-Smith. rejser. Naturh. Tid. 2, 113-116. The above is a translation of a speech read before the 1938: Planterester i Jelsfundet. In H. C. Broholm: Royal Danish Academy of Sciences and Letters, 16th Jelsfundet. Aarb. nord. Oldk. Hist. 1938, 5-6. February 1973. My sincere thanks are due to Mrs. 1939: Planterester fremdragne i tre høje i Haderslev Gertrud Købke Sutton for the work of translation. amt. In H. C. Broholm og Margrethe Hald: Skrydstrupfundet. Nord. fortidsminder 3, 18-31. List of Johannes Iversen's publications 1940: Blutenbiologische Studien. I. Dimorphie und Monomorphie bei Armeria. K. dansk Vidensk. 1928: Ober Isoétes in China und Japan. Dansk bot. Selsk. biol. Meddr 15, 8, 39 pp. Ark. 5, 23, 4 pp. 1940: Dimorfi og Monomorfi hos slægten Armeria - 1928: Uber die Spezies-Umgrenzung und Variation en blomsterbiologisk Undersøgelse (Autorref.). der Isoetes echinospora Durieu. Bot. Tidsskr. Naturh. Tid. 4, 35. 40, 126-131. 1940: Vegetations- og klimaperioder i Danmark efter 1929: Studien iiber die pH-Verhaltnisse danischer istiden, og Geologiske vidnesbyrd om »Svedje­ Gewasser und ihren Einfluss auf die Hydro- brug« i Danmarks yngre stenalder (Autorref.). phyten-Vegetation. Bot. Tidsskr. 40, (4), 277- Naturhist. Tid. 4, 6. 333. 1940: Hvorledes. nordboerne på Grønland gik til 1929: Lidt om plantelivet i vore søer. Nat. Verden grunde. Ledetråd v. Folkeuniversitetsundervisn. 13, 385-398. nr. 85, 4 pp. 1932: Isoetaceae. In Carl Christensen: The Pterido- 1940: Tørvemosernes geologi. Den konservative væl- phyta of Madagascar. Dansk bot. Ark. 7, 200. gerforen. Gjentofte kommune. Sept. 1940. 1933: (With E. K. Gabrielsen): Die Vegetation der 1940: Landnam i Danmarks Stenalder. En pollen­ Halbinsel Skallingen. I. Die Flora von Skallin­ analytisk Undersøgelse over det første Land­ gen. Bot. Tidsskr. 42, 355-383. brugs Indvirkning paa Vegetationsudviklingen. 124 Johannes Iversen

Land occupation in Denmark's stone age. A 1947: Plantevækst, dyreliv og klima i det senglaciale pollen-analytical study of the influence of Danmark. Geol. For. Stockh. Forh. 69, 67-78. farmer culture on the vegetational development. 1947: Steppe elements in the Danish late-glacial fauna Danmarks geol. Unders. (2), 66, 68 pp. (Abstract). J. ecol. 34, 234-235. 1941: Vore mosers vidnesbyrd om klimaets, plante- 1948: Palaebotany and pollen analysis. The humani­ og dyreverdenens forandringer gennem tiderne. ties and the sciences in Denmark during the Ledetråd ved Folkeuniversitetsundervisn, 118, second world war: 313-315. 4 pp. 1949: The influence of prehistoric man on vegetation. 1942: Østslesvigs natur. Danmark 2, 193-199. Danmarks geol. Unders. (4) 3, (6), 25 pp. 1942: Geological part. In M. Degerbøl og J. Iversen: 1949: Determinations of the specific gravity of the On a find of a sheat-fish (Silurus glanus L.) roots of swamp, meadow and dry-soil plants. from the ancylus period in Denmark. Vidensk. Oikos 1, 1-5. Meddr dansk naturh. Foren. 105, 443—446. 1950: (With Knut Fægri): Text-book of modern pol­ 1942: En pollenanalytisk tidsfæsteise af ferskvands­ len analysis. København: Einar Munksgaard, lagene ved Nørre Lyngby. Med bemærkninger 168 pp. om de senglaciale naturforhold i Danmark. 1950: Review. V. J. Kivenheimo: Untersuchungen Meddr dansk geol. Foren. 10, 130-151. iiber die Wurzelsysteme der Samenpflanzen in 1942: Diskussionsindlæg til J. Troels-Smith's fore­ der Bodenvegetation der Walder Finnlands. drag: Foreløbige Resultater af de geologisk­ Anm. bot. Soc. Zool.-Bot. Fenn Vanamo, 22.2. arkæologiske Undersøgelser i Aamosen. Meddr 1947. Oikos 1, 290-291. dansk geol. Foren. 10, 275. 1950: Contribution to discussion on Valdemar Mik­ 1942-44: Bliitenbiologische Studien. I. Dimorphie und kelsen: Menneskets indflydelse på vegetationen Monomorphie bei Armeria (Autorref.) Bot. i Præstø-Møn-egnen. Meddr dansk geol. Foren. Zentralbl. N.F. 36, 177-178. 11, 601-620. 1943: Et Litorinaprofil ved Dybvad i Vendsyssel. 1950: (With J. Troels-Smith): Pollenmorfologiske de­ Meddr dansk geol. Foren. 10, 324-328. finitioner og typer. Pollenmorphologische Defi­ 1943: (With Sigurd Olsen): Die Verbreitung der Was- nitionen und Typen. Danmarks geol. Unders. serpflanzen in Relation zur Chemie des Was- (4) 3, (8), 54 pp. sers. (Vortragsreferat). Bot. Tidsskr. 46, 136- 1951: Steppeelementer i den senglaciale flora og fau­ 145. na. Meddr dansk geol. Foren. 12, 174-175. 1943: Den danske vegetations udvikling belyst ved 1951: Pollenanalysers oplysninger om forhistorisk pollenstatistik. Salmonsen Leksikon-Tidsskr. 3, landbrug og vegetationsskifte. Salmonsen Leksi­ 116-120. kon-Tidsskr. 11, 86-88. 1944: Viscum, Hedera and Ilex as climate indicators. 1951: Lennart von Post 16. juni 1884-11. januar 1951. (A contribution to the study of the post-glacial Meddr dansk geol. Foren. 12, 115-119. temperature climate). Geol. For. Stockh. Forh. 1952: Lennart von Post 16. Juni 1884-ll.Januar 1951. 66, 463-483. Naturh. Tid. 16, 86-88. Portrait. 1944: Helianthemum som fossil glacialplante i Dan­ 1952: Late- and post-glacial forest history in Central mark. Geol. For. Stockh. Forh. 66, 774-776. Europe. Review: F. Firbas: Spat- und nacheis- 1944: De strenge vintre og den danske flora. Berling­ zeitliche Waldgeschichte Mitteleuropas nordlich ske Aftenavis, Kronik 12.1.1944. der Alpen. I. Allgemeine Waldgeschichte Jena 1944: Virkningen af vintrene 1939-42 på danske 1949. Oikos 2, 315-318. træer og buske. Naturh. Tid. 8, 56-57. 1953: Radiocarbon dating of the Allerød period. 1944: Nogle indikatorer for postglacialé klimaveks­ Science 118, 9-11. linger. Naturh. Tid. 8, 57-59. 1953: The zonation of the salt marsh vegetation of 1945: III. The dating of the bison finds. IV. Condi­ Skallingen in 1931-34 and in 1952. Geogr. tions of life for the large herbivorous mammals Tidsskr. 52, 113-118. in the late-glacial period. In Degerbøl, M. and 1953: Identification of difficult pollen types by means Iversen, J.: The bison in Denmark. Danmarks of structural characters (with discussion). Proc. geol. Unders. (2) 73, 33-62. 7th Intern, bot. Congr. Stockh. 1950, 873-876. 1945: (With M. Degerbøl): Om bison-fund i Dan­ 1953: Microscopic remains of late-glacial vascular mark og nogle bemærkninger om senglaciale plants discovered at Mapastown, Co. Louth. I naturforhold (Autorref.). Naturhist. Tid. 9, 40. Mitchell, G. F.: Further identifications of macro­ 1945: Planterne erobrer Danmark. Danmark 5, 18-24. scopic plant fossils from Irish Quaternary de­ 1945: Anmeldelse af V. Nordmann: Jordfundne patte­ posits, especially from a late-glacial deposit at dyrlevninger i Danmark, »Dansk Natur« 1944. Mapastown, Co. Louth. Proc. roy. Irish Acad. Nat. Verden 7, 303-304. (B) 55, 232-233. 1946: Geologisk datering af en senglacial boplads 1953: Origin and postglacial development of the flora ved Bromme. Aarb. nord. Oldk. Hist. 1946, ' of West Greenland in the light of pollen analysis 198-231. (with discussion). Proc. 7th intern, bot. Congr., 1947: Centaurea cyanus-pollen in Danish late-glacial Stockh. 1950, 634-36. deposits. Meddr dansk geol. Foren. 11, 197- 1954: Origin of the flora of Western Greenland in 200. the light of pollen analysis. Oikos 4, 85-103. 1947: (Contribution to discussion): Senglacialens nivå- 1954: Ober die Korrelationen zwischen den Pflanzen- forandringar och klimautveckling, and: Pollen­ arten in einem gronlåndischen Talgebiet. Vege- analysens principer och tillåmpning. Nordiskt tatio 5-6, 238-246. kvartargeologiskt mote 5.-9. november 1945. 1954: (Ed.) Studies in vegetational history in honour Geol. For. Stockh. Forh. 69, 215-217, 241-242, of Knud Jessen 29th November 1954. Danmarks 252. geol. Unders. (2) 80, 308 pp. Bulletin of the Geological Society of Denmark, vol. 24 1975 125

1954: The late-glaciål flora of Denmark and its rela­ 1964: (With Knut Fægri and' H. T. Waterbolk): Text­ tion to climate and soil. Danmarks geol. Unders. book of pollen analysis. Second revised edition. (2) 80, 87-119. København: Munksgaard, 237 pp. Second prin­ 1954: The late-glacial flora of South-Scandinavia and ting 1966. its recent relics. 8. Congr. intern, hot., Paris 1965: Undersøgelser i Draved skov over jordbundens 1954, C. r. Seances. Rapp. Communications lors og vegetationens degradering i postglacial tid. de Congrés, Sect. 3-6, 241-242. Overs. Kgl. danske Vid. Selsk. 1964-65, 52-53. 1954: The late-glacial flora of South-Scandinavia and^ 1965: (With Knut Fægri): Field techniques. In Hand­ its recent relics. 8th Congr. intern, bot., Paris book of palaeontological techniques. Eds. B. 1954, Rap. Communications avant Congrés, Sect. Kummel & D. Raup. 482-494. San Francisco 6, 265. and London: Freeman. 1954: Ny professor i botanik (Thorvald Sørensen). 1966: [Demonstration af nygravet afvandingsgrøft i Naturh. Tid. 18, 18-19. Draved skov]. In S. Hansen, A. Andersen og 1954: Pollen statistical evidence and experimental B. Jakobsen: 5-7th August 1965. Ekskursion til checks on neolithic forest clearance. Arch News Sønderjylland. Meddr dansk geol. Foren. 16, Letter 5, 9. 250-251. 1955: Stenalderens skovrydninger belyst ved pollen­ 1966: (With Knut Fægri): Terminologi in palynology. analyse og eksperiment. Overs. Kgl. danske Pollen Spores 8 (3), 407-408. Vid. Selsk. 1954-55, 57. 1967: Naturens udvikling siden sidste istid. Danmarks 1956: Neolitische Waldrodungen, beleuchtet durch Natur, 1, 345-445, København: Politiken. Pollenanalyse und Experiment. (Autorref.) Sit- 1967: Geologi og naturfredning. Meddr dansk geol. zungsber. Bernischen bot. Ges. 1955. Mitt. Foren. 17, 184-186. Naturf. Ges. Bern N.F. 13, XXX-XXXI. 1967: (With Knut Fægri): Introduction to L. von 1956: Forest clearance in the stone age. Scientific Post: Forest tree pollen in South Swedish peat Amer. 194, 36-41. bog deposits. Pollen Spores 9, 375-377. 1957: Istidsrelikter i Bornholms flora. Bornholms Na­ 1969: Retrogressive development of a forest ecosystem turh. Foren. 25 års jub. 35-37. demonstrated by pollen diagrams from fossil 1957: Den sidste istids klima og plantevækst. Overs. mor. Oikos Suppl. 12, 35-49. Kgl. danske Vid. Selsk. 1956-57, 61. 1969: (With C. Overgaard Nielsen, A. Noe-Nygaard 1957: Pollen-stratigraphic sequence in Europe post­ og J. Troels-Smith): Kommissionen for forsk­ dating the last glacial maximum. In R. F. Flint: ningsarealer. Beretning for 1968. Overs. K. Glacial and Pleistocene geology, Table 23-C, dansk Vidensk. Selsk. Virksomhed 1968-69, p. 397. New York: Wiley. 153-54. 1958: Pollenanalytischer Nachweis des Reliktencha- 1971: (With R. F. Flint): Pollen-stratigraphic sequence rakters eines jiitischen Linden-Mischwaldes. in northern Europe through the last 14.000 Veroff. geobot. Inst. Rubel, Zurich 33, 137- years. In R. F. Flint: Glacial and Quaternary 144. geology, 632-633, table 24-C. New York: Wiley. 1958: The bearing of glacial and interglacial epochs 1973: The Development of Denmark's nature since on the formation and extinction of plant taxa. the last glacial. Translation from Danmarks In Hedberg, O., (ed.): Systematics of today. Natur, 1, 345-445, 1967, by M. Robson. Editor: Uppsala Univ. Arsskr. 158,6 210-215. S. T. Andersen. Danmarks geol. Unders. (5) 1960: Le défrichement de la foret pendant l'Age de la 7-C. Geology of Denmark, 3. 126 pp. pierre. Naturalistes belg. 41, 53-64. 1960: (Ed. With E. Hyyppa and S. Thorarinsson): Proceedings of section 4: Chronology and climatology of the quaternary. Intern, geol. Congr. Rep. 21. Sess. Norden 1960, 4, 157 pp, 1 tvl. 1960: Problems of the early post-glacial forest devel­ opment in Denmark. Danmarks geol. Unders. (4) 4, (3), 32 pp. 1961: Pflanzenindikatoren des Klimas, des Bodens und anderer Faktoren wahrend des Quartars. 6. Congr. INQUA 1961. Abstracts, 115-116. 1962: Excursionsleder: P. Chr. Nielsen: Kongemosen og Draved skov. Dansk Skovfor. Tidsskr. 47, 21-35. 1962: Review. F. Fukarek: Die Vegetation des Darss und ihre Geschichte. Pflanzensoziologie, Bd. 12, Gustav Fischer, Jena, 1961. Bot. Tidsskr. 58, 245-246.. 1964: Plant indicators of climate, soil and other factors during the Quaternary. Rep. 6th Congr. Quaternary Warsaw 1961. 2 (Palaeobot.), 421- 428. 1964: Retrogressive vegetational succession in the post-glacial. J. Ecol. 52 (Suppl.), 59-70.