318 The Scottish Naturalist. 



cient time is allowed, it requires no great stretch of imagination 

 to suppose that these changes of circumstances and surround- 

 ings may produce such modifications as gradually to evolve 

 different species. 



After all, it is difficult to define what a " species " is : there is 

 infinite variety in nature. But having got into a slight digres- 

 sion, we will conclude by summing up the answers to the three 

 questions of our third head — viz., whence and when was our 

 alpine flora introduced, and how distributed? 



At the close of the glacial era, our country having no flora, 

 the Scottish alpine flora was introduced into the country across 

 the dry bed of the German Ocean from the south of Europe; 

 and climate has been the principal agent in its distribution and 

 dispersal. 



A NEW LIST OP THE FLOWERING- PLANTS AND PERNS 



OF ORKNEY. 



Edited by W. IRVINE FORTESCUE. 



ALTHOUGH more than one catalogue of Orkney plants 

 has been published, it is now many years since the last 

 of these appeared, and therefore another may not be without 

 interest. About thirty years ago Dr A. R. Duguid of Kirkwall 

 and Mr Robert Heddle compiled a MS. list of all the Orkney 

 plants they had met with, and this has been recently corrected 

 and added to by Dr J. T. Boswell of Balmuto, whose name is a 

 sufficient guarantee for the authenticity of all that has come 

 under his notice. 



Thanks are due to Dr Clouston for some interesting observa- 

 tions ; and Dr H. H. Johnston and others have added many 

 localities to the list ; and several plants which have been either 

 named or verified by Dr Boswell. 



The 59 N. latitude and the 3 W. longitude pass almost 

 through the centre of the Orkney Islands, while a parallelogram 

 47 miles from N. to S., by 37 miles from E. to W., will include 

 the whole group. The Pentland Firth, only 5^ miles wide at 

 its narrowest point, separates them from Caithness, while a gap 

 of 50 miles divides them from Shetland. The Mainland, which 

 is by far the largest island, occupies the centre of the group, the 

 islands to the north and south of it being called respectively the 

 North and South Isles. The total area of the Orkneys amounts 



