50 



MR FRANCIS J. LEWIS 



wide sea, which possibly has not been bridged in post-glacial times, their northern 

 position, the evidence of their heavy glaciation, and the fact that there are no lofty hills 

 on the mainland which would long nourish glaciers during the later stages of the glacial 

 period. 



Two districts were selected for examination : — 



(«) Walls- San dness district on the west coast of the mainland. 



(b) Part of the ridge running N. and S. along the centre of the mainland north of 

 Weisdale Voe. 



(a) The Walls-Sandness district is a broad peninsula of undulating moorland on 

 the west coast. The highest ground is reached in Sandness Hill (817 feet) and 

 Stourborough Hill (567 feet), elsewhere the moorland mostly lies between 200 and 300 

 feet above sea-level. 



Most of this peninsula is formed of sandstone and flags, giving a rounded aspect 

 to the hills and in striking contrast to the gneissose and quartzite rocks farther east, 

 where the hills are broken in outline and covered with dry Calluna moor. The 

 vegetation of the sandstones and flags where the peat is thick is composed of 

 Scirpus csespitosus, Eriophorum vaginatum, stunted Calluna vulgaris, Rhacomitrium 

 lanuginosum. 



The peat appears to be rapidly wasting away over the whole of the mainland, and 

 this is particularly marked on the hills in the Walls-Sandness region. 



Sections will first be described from the long valley running east and west 

 between Sandness Hill and Stourborough Hill and drained by the Burn of Dale, 

 where the peat is much channelled, the ridges between the channels being 

 covered with Scirpus c&spitosus, mounds of Rhacomitrium lanuginosum, stunted 

 Calluna. 



The general sequence found over this area is as follows : — 



Characteristic Plants. 



1. Scirpus c&spitosus. 



2. Erioplwrum vaginatum. 



3. Dense light-coloured structureless peat crowded 



with the stems of Calluna. 



4. Sulix Arbusculn. 



5. Betula alba. 



6. Sphagnum and Eriophorum vaginatum. 



7. Salix reticulata, S. herbacea. 



8. Potamogp.ton pectinatus. 



Accompanying Plants. 



1. Sphagnum, Calluna (scarce). 



2. 



3. 



4. Empetrum nigrum, Betula nana, Erica Tetralix. 



5. Corylus Avellana. 

 6. 



7. Betula nana. 



8. Menyanthes trifoliata, Viola palustris, Ranunculus 



repens, Equisetum sp. 



Sand and rock. 



There are certain interesting features in this sequence which merit more detailed 

 description. The basal layer contains the remains of an aquatic vegetation, and although 

 many of the plants have a wide range, all of them occur within the Arctic Circle at the 

 present time. The relation of these aquatic plants to the overlying arctic plants is very 

 similar to the aquatic vegetation underlying the arctic bed of Cape Wrath district already 



