124 H. MØLHOLM HANSEN 
We may distinguish between an area in which the moisture of 
the soil is entirely dependent on the precipitation throughout the 
year, an area whose moisture throughout the year depends also on 
the ground-water, and an intermediate area in which the moisture 
of the soil depends on the precipitation in the summer, while in the 
winter it is also dependent on the ground-water. This area is re- 
presented by the jadar vegetation. 
If, on a gently sloping surface, we pass upwards from the jadar 
vegetation, we may distinguish here between three different zones 
of moisture: a lower zone in the mo, where the influence of the 
ground-water is still demonstrable, the mo itself, where this influence 
no longer exists, and an upper zone (the melar vegetation), which, 
on account of its open vegetation, is exposed to a stronger desicca- 
tion than the more densely covered mo. 
If, from the jadar vegetation, we pass downwards, we can like- 
wise distinguish between three different zones of moisture: an upper 
myri formation, not very damp in the summer, a lower myri for- 
mation saturated with water, and finally the flöi, which is covered 
with water throughout the year. 
Thus we may distinguish between 7 different zones of moisture 
in Iceland. 
Zone I comprises the Elyna mo at Bjørk and the melar vege- 
tation on Lyngdalsheidi, at Leekjamot, and on Arnar- 
vatnsheidi. 
Zone II comprises the Arctostaphylos mo at Bjørk, the ordinary 
mo at Lyngdalsheidi, the high mo at Lækjamåt, the mo 
at Nordtunga, and the Betula nana mo on Arnarvatns- 
heidi. 
Zone III comprises the Calluna-Empetrum mo at Bjork, the moist 
mo on Lyndalsheidi, and at Lækjamôt, and the knolly 
mo on Arnarvatnsheidi. . 
Zone IV comprises the jadar vegetation at Bjork, on Lyngdals- 
heidi, and on Arnarvatnsheidi. 
Zone V comprises the Salix myri at Bjork and on Lyngdalsheidi, 
and the knolly myri on Arnarvatnsheidi. 
Zone VI comprises the Betula nana myri at Lækjamôt and Bjork 
and on Lyngdalsheidi, and the level myri on Arnar- 
vatnsheidi. 
Zone VII, finally, comprises the flöi vegetation at Bjork, on Lyng- 
dalsheidi at Lækjamôt, and on Arnarvatnsheidi. 
