320 The Scottish Naturalist. 



month. The mean temperature for fifty-four years is 45°.8i ; 

 the highest in shade for the last four years, 73 ; the lowest in 

 shade for the last four years, 7°.8; and the lowest by exposure 

 in 1 88 1, and also for the last fifty-four years, 2°.$ below zero. 



The winter, though usually mild, is a succession of westerly 

 gales, laden with salt-spray, and accompanied with drenching 

 showers, which blast the very heather-bushes on their western 

 side, except in the more sheltered situations. Heavy falls of 

 snow occur in hard winters. 



The summer is deficient in heat, and therefore trees do not 

 now succeed well in Orkney. The new growth being seldom 

 thoroughly ripened, they die back almost as much in winter as 

 they had gained during the warmer months. 1 



Hazelnuts and stems of trees, apparently birch, are fre- 

 quently found in the peat, showing that a warmer climate must 

 have prevailed in Orkney at one time. These trees rarely ex- 

 ceed six inches in diameter, and, judging from their remains, 

 must have been more or less stunted. 



They were probably confined to comparatively sheltered local- 

 ities. Dr Clouston mentions having seen a tree-stump in Berrie- 

 dale in Hoy several feet in diameter, one of its roots having a 

 diameter of about a foot at a distance of twelve feet from the main 

 stem. Doubtless the largest trees grew in the sheltered valleys 

 of Hoy, almost the only place where their descendants still 

 linger. 



Vegetation is from a fortnight to three weeks later than in the 

 middle and south of Scotland. 



It may be worthy of note that Fuchsia Mage/latiica thrives in 

 the open air in Orkney, though it does not attain the same size 

 as on the south-west coast of Scotland ; and Veronica decussata 

 succeeds even better, while Phonnium tenax flourishes with Dr 

 Traill in North Ronaldshay. 



Much remains to be done, especially in the North Isles, in 

 the way of recording the localities of plants. 



In the following list, the authority for a species or locality is 

 given immediately after it. B. stands for Dr J. T. Boswell of 

 Balmuto; D. for Dr A. R. Duguid ; and H. for Mr Robert 



1 I believe that the cause of trees not thriving in Orkney is that the gales 

 laden with chloride of sodium destroy the leaves where they are exposed to 

 the sea-winds and become incrusted with salt. Where trees are protected 

 by houses or walls, they grow much better than where exposed to the direct 

 action of winds from the sea. — T. T. B. 



