802 MR FRANCIS J. LEWIS 



that described in 1907 (3) lay on the surface of the boulder clay below the forest. In 

 most cases this lower arctic bed is 18 inches in thickness and is characterised by the 

 great abundance of Salix reticulata and S. herbacea in the lower levels, and of Potentilla 

 Comarum and Empelrum nigrum in the upper layers. In 1907 I described several 

 sections from the Dale of Burn, a broad, shallow valley on the north side of Stourborough 

 Hill. This peat was again examined during my last visit, and all the features previously 

 described were verified. The examination of the material from the first arctic bed in 

 1907 enabled me on this visit to recognise three zones which appear with some regularity 

 in each section. The most characteristic plants in the lowest zone are Salix herbacea, 

 S. reticulata, Be tula nana. 



The middle zone is characterised by the great abundance of Empetrum — in most 

 cases a considerable amount of the material is formed of the stems, leaves, and fruits of 

 this plant. Along with this are : — 



Mentjanthes trifoliata. \ Ranunculus foribundus. 



Carex atrata. Potentilla Sibbaldi. 



Gare.c fulra ? \ Ranunculus repens. 



Carex sp. I 



The uppermost zone has Potentilla Comarum as the characteristic plant ; occurring 

 with this are : — 



Carex paniculata . i Selaginella selaginoides (macrospores). 



Rubus Idseus. \ Lychnis diurna (?). 



All these three zones of the first arctic bed are usually present in the Dale of Burn, 

 but in other areas the lower zones are frequently wanting, and the layer characterised 

 by Potentilla Comarum rests upon the moraine. The comparison of the sections 

 described in 1907 with those examined last year brings this out in a very interesting 

 way, and shows very clearly that there were several stages in the vegetation before the 

 growth of the forest. It also demonstrates that the examination of only one section 

 in a peat bog may yield very fragmentary evidence, however careful an analysis may be 

 made of the samples in the laboratory, because in many cases the oldest zones are only 

 present in scattered spots, such as hollows in the surface of the boulder clay, and these, 

 of course, are not apparent until the sections are cut. 



The lower two zones are chiefly composed of plants which have an arctic or alpine 

 distribution, whilst the uppermost zone contains plants of wide distribution representing 

 merely a peat- bog vegetation in which arctics only occasionally make their appearance. 



Material from the peat below the forest stratum at the foot of Stourborough Hill at 

 220 feet yielded :— 



Potentilla Comarum. 

 P. Salisburgensis. 

 Potentilla Sibbaldi. 

 Lychnis diurna. 

 Carex echinata. 



C. distans var. fulva, Good (?) 

 C. sp. 

 C. sp. 



Selaginella selaginoides. 



