20 POPULAR GEOGRAPHY OF PLAINTS. 



getation, whenever it is investigated, will be very different 

 from those parts which have already been explored ; because 

 the wind, which in the higher latitudes generally blows 

 from the west, grows colder by travelling over great tracts 

 of land ; so that the temperature of the more eastern coun- 

 tries must be considerably lower than that of the western, 

 which the wind reaches after passing over the warmer sea. 



One great feature which distinguishes this zone from the 

 last, is the first appearance of trees ; some almost reach 

 North Cape, at the very extreme of the Scandinavian penin- 

 sula. If we had to guess what these hardiest of all trees 

 are, we should probably fix on Firs (Abies) ; and we should 

 have made a very intelligent guess, but a wrong one after 

 all. The elegant, delicate-looking Birch (Betula) it is, 

 with its light waving foliage and silvery bark, that stands 

 foremost to face the cold; it is said moreover to be the 

 most predominant of all the plants of this zone. It is the 

 nature of its thick bark which enables the Birch thus to 

 encounter the cold; for being a non-conductor of heat, 

 none of the vital warmth of the tree is able to escape. It 

 was not at all a bad guess about the Firs ; for, next to the 

 Birch, some species of the Fir appear in the greatest num- 

 bers. (Plate III.) There are even extensive forests of the 



