618 SECTIONAL TRANSACTIONS.— K. 



Concurrently with above afternoon session : — 



Joint Meeting with Sections D (q.v.) and I for communications on 

 Experimental Biology. 



Department of Forestry. 



Dr. T. W. WooDHEAD. — The Forests of Europe and their Development in 

 Early Post-glacial Times. 



Our knowledge of the development of forest vegetation in post-glacial times has 

 been considerably extended in recent years as the result of researches in many branches 

 of science, especially by Swedish investigators. De Geer, by a study of the stages 

 of retreat of the ice in the Stockholm region, and of the beautifully laminated clays 

 laid down in a post-glacial fjord, estabUshed a geochronology which places the last 

 Ice Age about 11,000 years ago. 



A.G.Nathorst.G.Andersson, A.Blytt and R. Semander havestudied the succession 

 of the floras in the post-glacial beds of Sweden, and the two latter have suggested the 

 following cUmatic periods : arctic ; sub-arctic ; boreal ; atlantic ; sub-boreal and 

 sub-atlantic. 



Studies by Brogger, De Geer and Munthe indicated post-glacial oscillations in the 

 Baltic during which characteristic shells were embedded in the littoral deposits, and 

 the dominant ones suggested names for the three successive stages and periods, viz. : 

 the Yoldia period, chmate arctic, culminating in a birch period ; the Ancylus period, 

 cUmate warm, dry, continental, a fir period ; and the Littorina period, chmate warm, 

 damp, oceanic, oak period. 



Another line of research is that initiated by G. Langerheim and further extended 

 by von Post, G. Erdtman and others. This consists of a statistical study of the tree 

 pollen grains found in peat, and the results are expressed in diagrams which show 

 the depth of the peat in metres ; the frequency of the pollen grains found at different 

 levels is expressed as a percentage of the total tree pollen in the horizontal scale, 

 the different species being indicated by signs. By this method pollen analyses have 

 been made of the microfossils in peat deposits over a wide area in N.W. Europe by 

 Erdtman and others, and many typical areas in the British Isles have thus been 

 investigated. 



Attention has also been directed to archaeological remains, carefully excavated at 

 the several levels in and below the peat, and these often provide a useful means of 

 dating the plant remains. 



Researches in Britain by Clement Reid and others showed that the interglacial 

 flora was much the same as the present one, and recently Wladyslaw Szafer has 

 obtained similar results for Middle Europe from investigations of deposits in six 

 locaUties in Poland. Here changes were indicated, both in climate and vegetation ; 

 which were closely similar to those enumerated by Swedish investigators for Scandi- 

 navia in post-glacial times. 



Peat investigations by the pollen statistics method produce results which fall 

 nto line with the above and indicate the following changes in climate and succession 

 in vegetation : — - 



Arctic : On ground bared by the receding ice, a tundra flora, including many 

 species common on our present moorlands. The first trees to appear were a species 

 of Salix and Betula. Remains of Palaeolithic man. 



Sub-arctic : Birch-heath forest becoming invaded by pines from the more southern 

 coniferous belt, remains of both often occur together. In Switzerland and Middle 

 Europe occur Pinus montana, P. cembra, Larix and further north Picea. Remains 

 of late Palaeohthic and Epi-Palaeohthic man. 



Boreal : Climate warm, dry, continental. The coniferous forests, with mountain 

 ash and bird cherry, were invaded by elm and oak, which marked the beginning of 

 degeneration of the pine forests. Erdtman contends that hazel was an early and 

 important pioneer in the development of the deciduous forest and suggests that 

 immigration in Britain, from the south-east, was in the following order : Salix, 

 Betula, Pinus, Corylus, JJlmus, Quercus, Alnus. During boreal time the deciduous 

 forests in N.W. Europe reached their cUmax. Up to this time peat was forming in 

 lake and swamp areas and enclosing relics of the arctic flora. Towards the end of 



