126 H. MØLHOLM HANSEN 
the latter 45. On Arnavatnsheidi, at a level of c. 500 m., the same 
formation shows a Ch percentage of 52. 
Taking the mosathembur vegetation of Lyngdalsheidi from 
altitudes of c. 250 m., 332 m., and 400 m, we get the following 
scale for the Ch percentage: 10—55—68, with a corresponding rise 
of the A percentage: 75 —90 — 100. 
Thus the influence of the cold on the Ch and A spe- 
cies is beyond all doubt. 
Table 26 shows the distribution of the life-forms in relation to 
the scale of moisture, A remarkable circumstance appears in con- 
nection with the chamaephytes. From a comparative minimum 
in zone IV (the jadar vegetation) the Ch percentage increases in 
value, upwards as well as downwards. This applies equally to 
the Bjork series, the Lyngdalsheidi series, and the highland series. 
In the Lækjamôt series the increase does not appear in the lower 
part of the scale for the halla myri series, whereas the rule seems 
to apply to the för myri series here. 
It is difficult to find any plausible reason why Ch should thrive 
best in the mo and the myri, and badly in the intermediate jadar. 
Anyhow, it is a fact that the environment in the jadar is unfavour- 
able to Ch. Species such as Empetrum nigrum, Vaccinium uligi- 
nosum, and Betula nana occur with a higher F.- percentage above 
as well as below the jadar. 
Possibly the cause may be found in the annual variations in 
the level of the water. It is of minor importance to Ch whether 
the moisture is great or small, if only it is the same ali the time. 
If great variations take place, as is the case in jadar where the 
plants grow now on damp, now on dry soil, Ch decline. 
On the heaths of Jutland it may often be observed how great 
variations in the water level tend to kill the chamaephytes, and at 
the level of moisture corresponding to the jadar, viz. the edge of 
the bog, the following facts may be observed. In the middle of 
the heath where the variations are only small, the chamaephytes 
play a prominent part in the composition of the vegetation, near the 
valley of the river where the variations are greater, the chamae- 
phytes disappear. In a series of investigations on this zone of 
moisture at Norholm Heath the former formation showed an average 
Ch percentage of 55, while the latter formation had only a Ch per- 
centage of 4. 
