ON THE PLANT REMAINS IN THE SCOTTISH PEAT MOSSES. 353 



The abundance of Betula alba and Corylus Avellana at the base of this peat and 

 resting upon the glacial deposits, is clear evidence that all this peat began to form 

 under temperate or genial conditions. No trace of Arctic plants has hitherto been found 

 either at the base or elsewhere in the Hebridean peat, thus showing that there is a 

 break of continuity between the glacial deposits and the peat that rests upon them. 

 This gap will probably be bridged by deposits yet to be found in other parts of the 

 Hebrides, but at present its existence deprives us of a useful datum line for determining 

 the age of this peat. The character of the basal layers of the peat would seem to 

 indicate more genial and dryer conditions than presently obtain ; for the greater part 

 of Sky e and North Uist (about 75 per cent, in one and 90 per cent, in the other) now 

 covered with peat was clothed with thick woods of birch and hazel, with some alder. 

 Such a type of vegetation is hardly represented in the islands at the present day. 

 Allowance must, however, be made for the fact that when this woodland period existed 

 the peat was extremely thin and presumably better drained than now. Immediately 

 above the woodland bed a decided change in the general flora is observed. Birch, 

 hazel, and alder become replaced by thick beds of Sphagnum, Phragmites, Digraphis, 

 Equisetum, Sphagnum, and Scirpus. Only one sign of any change in conditions is 

 given in these deep beds of marsh and moorland peat — at a depth of 3-5 feet from the 

 present surface the remains of Call una vulgaris become very abundant. This feature, 

 however, is so inconstant — appearing in some districts and disappearing in others — 

 that not much reliance can be placed upon it. 



The one feature that stands out distinctly from an examination of this peat is the 

 absence of Arctic plants and the constant presence of temperate forest remains at the 

 base, overlaid by marsh and bog peat. The question arises — Can the forest-bed here be 

 correlated with the lower buried forest described from the Southern Uplands ? If so, it 

 is difficult to account for the absence of the intercalated Arctic plants above the lower 

 forest-bed. The cause that induced the growth of Arctic plants in the Southern 

 Uplands after the dying out of the lower forest could scarcely have failed to affect the 

 Hebrides also. At the same time, it must be remembered that the Hebridean peat lies 

 at a low elevation near the sea, on flat or gently sloping ground, and far away from 

 any elevation exceeding 300 or 400 feet. It would thus tend to retain the features of 

 a marsh vegetation through any cold period characterised by great precipitation. The 

 climatic conditions that introduced an Arctic flora to the Southern Uplands would 

 certainly bring about local glaciation in such a mountain group as the Cullins, but the 

 districts under discussion would be well outside the range of the glaciers. 



The great similarity of these peat deposits to those in Kirkcudbrightshire (3) is 

 noteworthy. In that district a basal birch and hazel forest exists, probably contem- 

 poraneous with that of the Merrick-Kells and of the Tweedsmuir mosses, whilst the 

 Arctic bed of those districts is represented by thick beds of Phragmites in Kirkcudbright- 

 shire. If— as seems probable — the birch forest of the Hebrides is contemporaneous 

 with the lower buried forest of the lowland peat in Kirkcudbrightshire, then the upper 



