ON THE PLANT REMAINS IN THE SCOTTISH PEAT MOSSES. 57 



England of a change from temperate to arctic conditions during the later stages of the 

 glacial period. 



Fossiliferous beds of sand and peat yielding some evidence of changes in condition 

 have been described from Ballaugh in the Isle of Man by a Committee of the British 

 Association (7). 



In this case the evidence for a change from an arctic to a temperate flora is not so 

 conclusive as at Hoxne. Sandy silt, containing Salix herbacea amongst other plants, 

 is underlaid by loamy peat and Chara marl, from which arctic plants are absent, 

 although most of the plants belong to species of wide distribution. The presence of 

 Apus glacialis in the bed containing Salix herbacea certainly points to colder conditions 

 than the present. 



Numerous sections have been described in which an arctic plant bed occurs at the 

 base of the series overlaid by deposits containing a temperate flora. * 



In 1894 Bennie (8) described fossiliferous beds from Hailes, near Edinburgh, the 

 epecies being determined by Clement Reid. The lower beds rest directly upon the 

 boulder clay and contain Salix herbacea, S. polaris, S. reticulata, together with about 

 twenty other plants, some of which certainly do not now occur in the same regions as the 

 arctic willows. As the basal arctic bed occurs in a lacustrine deposit it is perhaps possible 

 that it contains fossils from slightly different periods. Be that as it may, it is certain 

 that the arctic willows indicate a very different type of flora to the temperate bed above 

 containing such temperate forms as Sambucus nigra, Prunus spinosa, P. Padus, Rubus 

 Idxus, Crataegus Oxyacantha. These plants occur mixed with others usually considered 

 as weeds of cultivation, such as Chrysanthemum segetum, JEthusa Cynapium, Linum,, 

 which suggests that the temperate bed belongs to a comparatively late period. If there 

 is no break in continuity between the basal arctic bed and the overlying deposits 

 containing temperate plants and weeds of cultivation, the evidence tends to show that 

 the arctic plants belong to a period much more recent than the retreat of the ice-sheet. 



Similar arctic plant beds have been described from Corstorphine (8), Faskine (9), 

 Dronachy (10), by Bennie, and from Crianlarich by Dakyns (11), the plants from the 

 various sections having been determined by Clement Reid. 



Numerous other examples might be quoted from the lists given by Reid (11), but 

 enough has been said to show that arctic plant beds are of wide occurrence in Britain. 

 The arctic plants of Hailes, Corstorphine, Dronachy and Crianlarich apparently belong 

 to the same stage, and the presence of Salix polaris in these deposits in the lowlands of 

 Scotland suggests that they can hardly be younger than the first arctic bed underlying 

 the lower forest in the peat mosses. 



The section at Hoxne, where an arctic bed overlies a deposit containing temperate 

 plants, gives the same sequence as the south of Scotland and Shetland peat where the 

 lower forest is overlaid by an arctic zone, though the fact that the Hoxne deposits rest 

 upon the chalky boulder clay and the Southern Upland mosses upon morainic material of 

 a later stage makes it probable that the Hoxne temperate bed is older than the Lower 



TRANS. ROY. SOC. EDIN., VOL. XLVI. PART I. (NO. 2). 8 



