71. AMENTIFERiE. 381 



North limit in Orkney, Sutherland. 



Estimate of provinces 18. Estimate of counties 80. 



Latitude 50 — 60. British type of distribution. 



A. A. regions. Inferagi'arian — Midarctic zones. 



Descends to the coast level, in the Peninsula. 



Ascends to 700 yards, or upwards, in East Highlands. 



Range of mean annual temperatiue 52 — 40. 



Native. Sylvestral, Ericetal. Omitted from the lists 

 for Shetland, Hebrides, Isle of Man, and some tracts of 

 small extent in England ; so that possibly the estimate of 

 75 might come nearer to the tnie number of counties than 

 is that of 80. This tree is frequent on the Highland moun- 

 tains up to 600 or 700 yards ; but rare at any greater ele- 

 vation ; although, as was remarked in my earliest volume 

 on plant-geography. Outlines, 8fc., I think to have seen it 

 much higher than 2000 feet, — certainly so, in form of a seed- 

 ling plant of it on the acclivity of Ben Nevis. The Betula 

 alba of authors has been subdivided into several species, 

 under the names of glutinosa, pubescens, pendula, &c. 

 There certainly are great variations in the forms of the 

 leaves and fruit, but I have been unable to satisfy myself 

 about the distinctness of the alleged species on examining 

 a large series of specimens, and likewise very numerous liv- 

 ing trees in England and the Highlands. The extreme 

 forms of B. pendula and B. glutinosa are very different ; 

 but the intermediate forms are numerous, and look like 

 links of connexion. 



/u. /^ /// y/. f^y 994. Betula nana, Linn. 



Area * ^u ******** 11 * 13 14 15 16 17. 

 South limit in Northumberland, Berwick, Lanark. 

 North limit in Ross, Aberdeen, West Inverness. 



