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XIII. — The Plant Remains in the Scottish Peat Mosses. By Francis J. Lewis, 

 F.L.S., Lecturer in Botany, University of Liverpool. Communicated by 

 Professor Geikie, LL.D., F.R.S. (With Four Plates.) 



PART II. 



The Scottish Highlands. 



(MS. received June 8, 1906. Read June 18, 1906. Issued separately October 19, 1906.) 



An investigation of the peat mosses in some districts of the Scottish Highlands was 

 made in 1905, with a view of comparing the features found there with those already 

 recorded from the Southern Uplands in 1904. The salient feature met with in the 

 Southern districts was the existence in all the older mosses of an upper and lower 

 forest-bed, with a zone of Arctic plants intercalated between. The existence of this 

 Arctic plant bed, stretching at the same horizon through the peat in districts widely 

 separated, indicates a lowering of temperature which must have obtained over much 

 greater areas ; for the conditions implied by the presence of an Arctic vegetation at low 

 levels in the South of Scotland would suffice — precipitation being great enough — to 

 produce glaciation in the Highlands. It was desirable to find evidence in the North 

 for or against that view. The work has also been taken up with the object of 

 ascertaining the changes in distribution of the British Flora since late glacial times. 

 In order to do this, systematic investigations must be made, not merely in a few 

 districts, but throughout Great Britain generally. Observations made farther north, in 

 the Shetland and Faroe Islands and in Iceland, might be expected to throw light upon 

 the origin of the flora of Greenland. The Alpine members probably survived on 

 nunataks through the glacial period, but lowland plants must almost certainly have 

 been destroyed by the rigours of that period. Warming (1) brings forward observa- 

 tions which tend to disprove the existence of a land bridge through Scotland, by 

 Shetland, Faroe, and Iceland, to Greenland, and the immigration of the European 

 elements in the Greenland flora along that bridge. Investigation of the peat in those 

 islands would show whether they have formed a link in that hypothetical highway of 

 plant immigration to Greenland. 



By the researches of Clement Reid (2) on deposits in Norfolk and the South of 

 England our knowledge of the pre-glacial and early inter-glacial flora has been con- 

 siderably increased, but nothing is known of its history later than the mid-glacial 

 period. Yet the geological evidence for considerable climatic changes during late 

 glacial and so-called post-glacial times is weighty, and we can hardly doubt that such 

 climatic changes must have produced corresponding changes in the distribution of the 

 TRANS. ROY. SOC. EDIN., VOL. XLV. PART II. (NO. 13). 47 



