Botanical Excursions into the Highlands. 357 



Schoenus nigricans, \ ^-Various moors in the north of Sutherland. 



Sedum album, I y 2 Roofs in Forfar, where it was introduced by Mr Don. 



Silene acaulis, var. flor. alb. I In considerable quantity on the summit of 



Ben-na-muic-dui, and on the south side of Glen Dole. 

 Sonchtts aipimis, 1, 2 Found in five new stations in Glen Dole and Glen 



Isla by Dr Wight, Dr Greene of Boston, U. S., and Dr Greville. The 



first party found it only in the old station, where, from being constantly 



plundered, it is becoming weaker every year. Fortunately some of the 



new stations are wholly inaccessible. 

 Stratiotes aloides, 1 In the Loch of Forfar, where it was introduced by Mr 



Don. 

 Thlaspi alpestre, 2. — New to Scotland. I gathered a few specimens at the 



foot of the rocks in Glen Isla. 

 Veronica alpina, 1, 2, — Exceedingly common all over the banks of the White 



Water, in Glen Dole, upon the Fee, in Glen Isla, Glen Callader, and 



the Aberdeenshire mountains near Castletown. It is not common in 



the other parts of Scotland which I have visited. Mr Watson found a 



few specimens on Cairn Garidh. 

 saxatUis, 1, 2 Common in Glen Dole ; but in much larger quantity, 



and of much greater size, in Glen Isla. 



Woodsia hyperborea, 2 A single tuft was found by Dr Greville in Glen Isla. 



ilvensis, 1.— Found by Mr Watson sparingly on the cliff with Ooeytropis 



campestris. 



Observations of Mr Hewett Watson *. 



Absolute altitude is of so little importance in the geography 

 of plants, that my attention was for the most part hmited to 

 the observation of their relative heights in regard to each other. 

 For this purpose, however, it was necessary to determine the 

 heights of a few species most commonly met with, as points of 

 comparison and reference. The following are the averages of 

 various observations made near the places mentioned ; the nu- 

 merals denoting the altitudes above the sea-level in feet "I-. 



• We trust Mr Watson will continue his interesting investigations, and 

 in his next communication inform us how his heights of stations were ascer- 

 tained — Edit. 



•\ Arbutus alpina does not grow in Clova or Braemar. Its southern li- 

 mit in Britain is probably near Fort William. There its lowest limit (ave- 

 rage of three observations, several miles distant) is at 1970 feet ; on the north 

 side of Ben Shith (pronounced Ben Hee), near Tongue, 970, and by Loch 

 Erriboll, fourteen miles west of Tongue, about 250. (These last measure- 

 ments give a good example of the influence of longitude, particularly when 

 taken in conjunction with the descent of Thalictrum alpinum to the shores of 

 Keoldale, a few miles to the westward of Loch Erriboll, as noticed in the ex- 

 cursion in 1827. Mr Watson did not find it so low in his route, but was par- 



