380 71. AMENTIFER^. 



the sunny side of rocks, where it may be considered par- 

 tially in a condition approximating to that of the fruit trees 

 which are trained on walls in our garden. Its usual upper 

 limit otherwise would seem to be at about 400 yards of ele- 

 vation, in the Highlands, nearly on a line with the Pteris 

 and com cultivation. Is it a native in the Hebrides ? 



992. Alnus GLDTINOSA, imw. "^ AS~^y 



Area general. 



South limit in Cornwall, Isle of Wight, Kent. 



North limit in Hebrides, Sutherland. 



Estimate of provinces 18. Estimate of counties 80. 



Latitude 50 — 59. British type of distribution. 



Agrarian region. Inferagrarian — --Mrdagrarian zones. 



Descends to the coast level, in the Peninsula. 



Ascends to 550 yards, in East Highlands. 



Range of mean annual temperature 52 — 41. 



Native. Sylvestral, Paludal. Absent from the Floras 

 of Shetland and Orkney ; nor am I prepared to cite any 

 authority for its occurrence in the Isle of Man. At the 

 height of 1500 feet, in Aberdeen and Moray, I have seen 

 trees of the alder full three feet in girth, and smaller ex- 

 amples at rather a higher elevation. Both this tree and 

 the Corylus might be considered to attain the inferarctic 

 zone. But if so, they are so local within the arctic region, 

 as barely to belong to it. 



993. Betula alba, Linn. 



Area general ? 



South limit in Cornwall, Isle of Wight, Kent. 



