148 H. MØLHOLM HANSEN 
This distribution is especially very plainly seen in the highland 
scale. As everywhere else A 3 attains its maximum in the highest 
class, which is relatively unfavourable to A 2. The maximum of 
this group is the second or third highest class, while A 1 does not 
attain its maximun until yet another degree lower in the scale. In 
the lowest class there is a rise in the A percentage which would 
seem to suggest that too large an amount of snow restricts the 
growth of the southern species but promotes that of the arctic 
species. The Salix herbacea, Sibbaldia procumbens and Anthelia 
societies previously cited must be assumed to be a development 
resulting from this fact. 
The change in the proportion of A and E species as we pass 
from snowbare to increasingly snow-covered vegetations is the same 
whether expressed in frequency sum numbers or in the species num- 
bers alone. This is very plainly evident from the species groups spectra 
in table 8 which have been calculated from Ingimar Oskarsson’s 
species lists from Vestfirdir. The series melar — heather and mo > 
herbfield and birch copse corresponds to the above-mentioned snow- 
covering classes I—II—III. The percentage amounts of A, A 3, and 
E 3+2+1 species in the various groups of vegetation are as follows: 
A per- A3per-- E342-+1 
centage centage percentage 
Hishland'melar: ......... 82 24 4 
Iawlandmelar . 20.5... 60 22 23 
Heather and mo veg. ... 50 13 32 
Herbfield and birch copse 23 fl 48 
FLOR ISPHIMES ete Lei: » > 75 
Even though the values do not coincide with those given in 
table 30, the correspondence in the variations of the series of figures 
is beyond doubt. 
A comparison between the species group spectra for the various 
types of vegetation, partly in the different parts of the country, 
partly at different heights above sea-level, will be of interest. 
Thus the melar vegetation in the south country has a lower 
A percentage and A 3 percentage, but on the other hand a higher 
E 3+2--1 percentage than the corresponding vegetation in the north 
country and the highland tracts. The numerical values are as follows. 
