1915] 



WILLE FLORA OF NORWAY 65 



It was formerly supposed that the largest rainfall was on 

 the outermost islands off the west coast of Norway, and that 

 this was the cause of the Atlantic vegetation that is found 

 there, with such characteristic plants as Hymenophyllum 

 peltatum, Erica cinerea, Scilla verna, Vicia Orobus, etc. But 

 more recent investigations have shown that the rainfall is 

 greater a little way in from the coast, where the mountains 

 begin. In Hovlandsdal, near the Sogne Fjord, a mean rain- 

 fall has been observed of 3,178 mm., and at Skaanevik, near 

 the Folgefon, 2,945 mm., whereas the outermost islands off 

 Bergen show a rainfall of only 1,300 mm., and off Fiord of 

 1,900 mm. It is, therefore, clear that the occurrence of the 

 above-mentioned Atlantic plants on the outermost islands is 

 due not to a larger rainfall, but to a milder winter tempera- 

 ture. 



There are, of course, species of plants that cannot thrive 



in the great humidity of the West Coast; but as there are 

 also localities with comparatively dry soil, it may be rather 

 the low summer temperature than the large rainfall that pre- 

 vents them from thriving. 



The importance of the soil for vegetable growth appears 

 to depend, in Norway, mainly upon whether the soil is rich, 

 or deficient, in lime. In addition to its chemical influence, a 

 calcareous subsoil, especially when consisting of calcareous 

 slate or limestone, is of consequence from the fact that it 

 forms a warm soil. In Norway, therefore, most of the 

 southern species are found only in the limestone country 

 surrounding the Skien Fjord and the upper part of the Kris- 



tiania Fjord. 



The terrestrial plants of Norway may be divided into five 



zones, according to the ability of the plants to ascend the 



mountains and extend northward in their growth, that is to 



say, according to their dependence on the mean temperature 

 of the summer. These zones are here indicated by the upper 

 limit of a characteristic species of plant. 



I. THE QUERCUS PEDUNCULATA ZONE 



In the east of Norway this tree is found as far as Lake 

 Mjosen (60° 45' N.), and in the west up to Nordmore (62° 



