THE SEQUENCE OF PLANT REMAINS IN 

 THE BRITISH PEAT MOSSES 



By FRANCIS J. LEWIS, F.L.S. 



Lecturer in Geographical Botany, University of Liverpool 



Although peat deposits occur throughout Europe they attain 

 their greatest extent and depth in the north-west of the Con- 

 tinent. Precise figures are not obtainable, but these deposits 

 cover a considerable proportion of the whole of Germany, 

 Denmark, Sweden, and the Jura range in Switzerland. The 

 interest of such deposits lies in the fact that they consist wholly 

 of the remains of plants which have existed over these areas 

 during a long space of time. Further, when it is remembered 

 that all the larger peat areas that have been examined show 

 a definite stratification, and that the lower layers frequently 

 contain the remains of an arctic vegetation in regions which 

 now support a temperate flora, it will be seen that from a 

 botanical and geological point of view it is important to make 

 a systematic investigation of the successive strata over con- 

 siderable areas. Such investigations might be expected to 

 throw light upon the changes in distribution undergone by 

 the British flora since its immigration from the Continent in 

 post-glacial times, and also give direct palaeontological evidence 

 for a long period of time during which, geologists are agreed, 

 many climatic changes have occurred, though the amplitude of 

 such changes is still a matter of controversy. Differences in 

 climatic conditions of comparatively small amplitude would 

 certainly affect the character and distribution of vegetation to 

 a greater degree than the alluvial drifts which were deposited 

 whilst those changes were in progress. 



The researches of Continental botanists and geologists during 

 the last thirty years have shown that systematic investigation of 

 peat deposits are capable of giving definite and unmistakable 

 evidence upon these questions. Since 1870, when Nathorst (1) 

 first described the occurrence of an arctic vegetation in fresh- 

 water clays at the base of the peat mosses near Alnarp in 



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