ON THE PLANT REMAINS IN THE SCOTTISH PEAT MOSSES. 45 



The peat immediately above the basal marsh vegetation forms a well-marked 

 horizon, as it is entirely made up of the remains of Betula nana, stems and leaves, and 

 scales of the female catkins, and Salix Arbuscula, Empetrum nigrum, and Arcto- 

 staphylos alpina. None of these plants are characteristic of swamps or marshes, but 

 Betula nana occurs in peat bogs at fairly high elevations, and the other plants are 

 abundant on mountain slopes and summits. Comparing the Betula nana bed and the 

 Pinus sylvestris bed (Nos. 5 and 2) in the last section, it is evident from the plants 

 that the peat of these two beds was not laid down under the same conditions. No 

 changes in the drainage or the character of the peat would cause a forest of Pinus 

 sylvestris to replace a close growth of Betula nana, Salix Arbuscula, Empetrum 

 nigrum, and Arctostaphylos alpina. At the present day these two types of vegetation 

 have their own altitudinal range, and are never found associated. In the case of the arctic 

 bed (No. 5) we are dealing with a depression of the arctic zone. The Pinus sylvestris 

 bed represents a return of the forest zone to at least its present altitudinal limits. 



The upper forest bed (zone No. 2) does not apparently show the double tier of trees 

 so characteristic in most of the Highland areas. The only indication of such a feature 

 is in Section I., where Pinus sylvestris is underlaid, first by a Sphagnum bed and 

 then by a layer of birch. But the wood is small in size, it is absent in many sections ; 

 and where present it is always mingled with quantities of Eriophorum and Sphagnum ; 

 a condition of things very different from that of a true forest bed, where the peat 

 contains dry moorland plants and shows unmistakable signs of having been accumu- 

 lated slowly. On the other hand, this shrubby birch agrees in character and in position 

 with that described from the Spey-Findhorn and Findhorn-Nairn watersheds, Coire 

 Bog, and Caithness in 1906 (3). The general sequence of the peat in this area agrees 

 very closely with that in the areas just mentioned. 



3. The Outer Hebrides. 



Peat in the Island of Leivis (one-inch Ordnance Survey — sheets 99, 105). — 

 Following on the examination in 1905 of the peat in North Uist and Skye, it was 

 decided to examine part of the extensive peat in the Lews to see what light it would 

 throw upon problems raised by the peat in Skye and Uist. In addition, the distance 

 of the island from the mainland and its position on the extreme N.W. edge of the 

 Continental plateau made it desirable to ascertain if the strata represented on the 

 mainland also appeared there. 



The whole of the island north of Loch Erisort is practically peat-covered, with the 

 exception of small cultivated areas near the townships on the coast. 



For a distance of 32 miles northward of Loch Erisort the island does not rise above 

 900 feet, and most of it is under 400 feet. The central portion is almost level, and 

 forms an unbroken peat bog over which are scattered scores of lochs. In the southern 

 region towards Loch Erisort they are so numerous that the island consists of almost 



