176 H. MØLHOLM HANSEN 
to distinguish between a series of zones, a lower and an upper high- 
land zone, and a nival zone. 
The lines between these zones can be drawn approximately as 
follows. The lower highland zone extends from the 300 m curve 
to the 600 m curve and has a Ch percentage of from 20 to 25; 
the upper highland zone extends from the 600 m curve to the 800 m 
curve and at its upper limit has a Ch percentage of 40; the nival 
zone is the zone between the 800 m curve and the snow-line; it 
has a Ch percentage of 40—50. Even though the position of the 
limits of the zones must be taken with some reservation, they agree 
well with conditions in the adjacent countries. Thus in Scotland 
the 20 p.c. Ch biochore lies at c. 800 m above sea-level, in the 
Faeroes at c. 500 m, in Greenland the 20 p. ec. Ch biochore lies at 
the level of the sea in 60—61° N. 
4. An investigation of the peculiarities of the flora in the separate 
parts of the country and the altitudinal zones shows that the differ- 
ences are especially due to differences in temperature. The differ- 
ences in the vegetation are likewise due to this factor. 
The temperature of the soil differs according to the degree of 
snow-covering and water-covering, though in different ways. In the 
winter the geiri vegetation with its constant snow-covering as well 
as the flöi vegetation with its constant water-covering are protected 
from the frost. Hence the result in both cases is a vegetation con- 
sisting principally of southern species, even though the two areas 
have not one species in common, while the snow-bare vegetation, 
melar and mosathembur, which is most exposed to the cold of 
winter, consists principally of arctic species, and the intermediate 
areas, mo, jadar, and myri, both as regards environment and bio- 
logical conditions, occupy an intermediate position. 
In the summer the flöi vegetation has a constant covering of 
water, the specific heat and evaporating heat of which does not 
allow of so high a degree of heating as an equal amount of heat 
produces in the geiri vegetation. The result is, then, that a series 
of the most heat-loving species do not occur on water-covered soil, 
but only in the geiri. Soil with a constant water-covering is warm 
in winter, but cold in summer. The soil with a constant snow- 
covering in the winter is warm both summer and winter; both these 
circumstances are strikingly manifested in the composilion of the 
vegetation. | 
The sequence dry, moderately moist, and moist soil, or mo, 
