134 H. MØLHOLM HANSEN 
in summer, though in less degree than Zone I. Hence the same 
types of plants occur here. 
C. Jadar (Zone IV). As previously indicated, this zone must 
be regarded as relatively warm in winter and warm in summer, 
owing to the variations in the level of ground-water. Hence the 
result is that the vegetation consists in marked degree of southern 
types, EL Th, and E species. 
D. Myri (Zones V—VI) is warm in the winter but cold in 
the summer. Hence southern plants requiring much heat (E 2+1 
species) and northern plants requiring much cold (A 3 species) thrive 
badly or are unable to thrive here. As a matter of fact the vegeta- 
tion consists of southern plants requiring little heat (E 4+3 species) 
and northern plants requiring little cold (A 2+1 species). 
E. Flöi (Zone VII). Here the vegetation is covered by so deep 
a layer of water that the frost hardly reaches it in the winter. 
Hence it is never exposed to the conditions required by arctic plants; 
consequently these are absent at any rate in the lowlands and as 
compared with the myri formations. In the summer, too, the vegeta- 
tion is covered by water. The heat which benefits the plants on 
drier soils is latent in the water here. The result is a relatively 
low temperature which excludes the southern plants requiring more 
heat. Hence the species group spectrum is compressed to the central 
parts of the spectrum. 
Between halla myri and för myri there is a peculiar difference 
in regard to the species group spectrum. 
As previously mentioned, the difference between the halla myri 
and the för myri is this, that halla myri appears where the ground 
water comes to the surface, while the för myri is dependent for 
its moisture on the surface precipitation water. While the tem- 
perature of the water is to a certain extent dependent on the tem- 
perature of the air in the latter case, the temperature of the water 
in the halla myri is dependent on that of the ground-water, which 
again is equal to the annual mean temperature of the locality in 
question. In the winter there will be a constantly varying amount 
of relatively warm water in the halla myri to be cooled, whereas, 
in the för myri, there will be a constant amount of water to be 
cooled, and the result must be that the temperature of the 
halla myri in the winter must be higher than that of the 
for myri. In the summer the reverse must be the case. The 
heat in the halla myri will have a constantly varying amount of 
