3 i4 SCIENCE PROGRESS 



In the Southern Uplands, Hebrides, and the Shetlands the 

 Lower Forest is well preserved, the trees being Betnla alba, 

 Corylus avellana, Alnus glutinosa. The list of accompanying- 

 plants is not large, as the peat is chiefly formed of wood debris 

 and bark. Inferences as to temperature drawn from these 

 trees alone are inconclusive, but certain features presented 

 by the distribution of the forest bed bear directly upon the 

 general climatic conditions of that time. The presence of a 

 buried forest extending to the western coast of Shetland 

 points indubitably to the fact that the path of the Atlantic 

 cyclonic systems must then have been different from that of 

 the present day. Trees are now entirely absent from Shetland, 

 although many attempts have been made to form plantations 

 in sheltered spots. Planted in gardens, ash, rowan, and birch 

 grow as high as the surrounding walls, and are then stunted 

 by the winds, so that the trees appear to be shorn off at 

 the level of the protecting wall. If this takes place at the 

 inland and more sheltered spots, it is still more difficult to 

 account for the presence of the buried forest near the cliffs 

 of the west coast, where the full force of the Atlantic gales 

 is felt, as they succeed one another during the greater part 

 of the year. As the mean annual temperature of the Shet- 

 lands is perhaps higher than many parts of Britain which 

 are tree-clad, the absence of trees in these islands must be 

 due, not to temperature, but to the force of the salt-laden 

 winds. 



The accompanying flora of the Lower Forest contains many 

 plants of wide distribution which do not give any definite 

 evidence with regard to temperature. The zone also contains 

 other plants which are not usually found accompanying arctic 

 plant associations, such as Ajuga rcptans, Ranunculus lingua, 

 Lychnis diurna, Salix purpurea. 



But the most significant fact is that none of the characteristic 

 arctic plants of the first and second arctic beds are to be 

 found in the Lower Forest bed, though quantities of material 

 from the south of Scotland, the Hebrides, and the Shetlands 

 have been worked through. If it still be urged that there is 

 no direct proof that the Lower Forest bed was accumulated 

 under temperate conditions, one may ask what was the reason 

 for the disappearance of the characteristic plants of the first 

 arctic bed during this period, and why should these typical 



