BOOK III 

 FLORIST1C REGIONS 



CHAPTER I 



THE NORTHERN ZONE 



THE surface of the globe is, as we have seen, divided 

 into three main zones, so far as the incidence of light 

 and heat are concerned, Northern, Tropical, and 

 Southern. The differing capacities for light- and heat- 

 absorption of land and water, and the interference of 

 land-massls modifying the courses of ocean-currents, 

 prevent these zones from coinciding with lines of latitude. 

 In area of land they are very unequal, the Northern 

 comprising most of the great belt of almost continuous 

 land surrounding the Arctic Ocean, whilst the Southern 

 includes only the narrowing southern portions of South 

 America and Africa, half of Australia, New Zealand, and 

 the now barren Antarctica. 



The most striking features in the Northern Zone as 

 a whole are its pure forests of needle-leaved Conifers, 

 catkin-bearing and other deciduous Dicotyledons, and 

 numerous herbaceous species. Still mainly considering 

 temperature, we may divide it primarily into three sub- 

 zones, the Arctic, Northern Temperate, and Southern 

 Temperate. Of these, the Arctic Sub-zone constitutes one 

 fairly homogeneous floristic region extending down to 

 lat. 52 N. in Labrador, but ending rather north of the 

 Arctic Circle in Europe, its southern boundary being the 

 northern limit of trees. 



AJRCTIC REGION. The Arctic Region is characterised 

 by its long cold winters, when the sky is clear, there is 

 but little precipitation, and strong dry winds sweep away 

 the scanty snow ; and by its short summers, when, owing 

 to the low altitude of the sun, the temperature is cool, 

 but fogs are frequent. The whole period of vegetation 



95 



