1915] 



WILLE — FLORA OF NORWAY 63 



and Sorbus Aucuparia, 7.7°C. ; Populus tremula, 7.6°C. ; 

 Betula odorata, 7.5°C. ; Juniperus communis var. nana, 5.3° 

 C. ; and Betula nana, 4.3°C. 



As the mean temperature of summer decreases with in- 

 creasing height above sea-level very nearly 0.6° C. per 330 

 feet, the distribution of plants is greatly influenced by the 

 circumstance that Norway is a mcuntainous country, its 

 highest mountain, Galdhopiggen, being 8,095 feet in height, 

 and thus within the region of perpetual snow. But a pecu- 

 liarity of the Norwegian mountains is that they form broad 

 (as much as sixty-two miles broad}, undulating mountain 

 plateaus, which are intersected by deep or shallow valleys, 

 where there are narrow lakes or small rivers. The edge of 

 these mountain plateaus, in the south of Norway, lies at a 

 height of from 2,950 to 3,280 feet above the sea, so that Picea 

 excelsa and Pinus sylvestris disappear slightly below this 

 height, the edge of the plateaus and the lowest valleys that 

 intersect them being covered with Betula odorata. The great 

 mass of the mountain plateaus, which rise above the birch- 

 limit, is thus treeless. 



It has been calculated that there are 26,333 square miles 

 of forest land in Norway, of which 73 per cent consists of 

 Picea excelsa and Pinus sylvestris, while the remaining 27 

 per cent is mainly Betula odorata with a little Betula verru- 



cosa, Quercus pedunculata, and Q. vessiliflora, and a very 

 little Fagus sylvatica in the south. 



The vegetation limits are lower not only toward the north, 

 as one would expect, but also towarc. the west, as they are 

 lower near the sea than inland. This will be seen from the 

 following height-limits in feet : 



Snow-line Birch-limit Pine-limit 

 ft. ft. ft. 



Gausta in Telemarken (south of 



Norway) 



• • 



3450 3024-3113 



Vos (west of Norway) 3936 3359 1994 



Snehaetta, in the Dovre Mountains 



(central Norway) 5375 3464 2880 



Rodo in Helgeland (just within 



the Arctic Circle) 3280 .... 777 



Alten in Finmark (70° N. Lat.) . 3516 1476 777-1023 



