The Botany of Iceland - 01.12.1930, Side 153

STUDIES ON THE VEGETATION OF ICELAND
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the Arctostaphylos mo. Ljmgdalur a, b, c, d, and e are respectively
mosathembur, melar, transitional forms between mosathembur and
mo, mo and geiri. Thrasaborgir a, b, and c are respectively mosa-
thembur, mo and geiri. Lækjamót a and b are melar and tbe high
mo. Norðtunga a, b, and c are the mo, the vegetation in the forest
glades, and the vegetation on the forest-ground. Arnarvatnsheiði
a, b, c, d, and e are respectivelv melar, Betula-nana rno, the knolly
mo, the vegetation on the sides of the snow patches, and the
vegetation on the bottom of the snowr patches with a northern
exposure.
A comparison of the mean values has been attempted and is
likewise given in the table. The scale is divided into three divisions.
I represents the types of vegetation bare of snow, melar (I b), and
mosathembur (I a). II represente types with normal snow-covering,
viz. the mo. III represents types of vegetation with a constant
snow-covering, i. e. geiri and forest. In the calculation of the mean
values the deviating localities have been omitted, viz. Bjork a and
b, Lýngdalur c, and Norðtunga c. The ligures under I a are thus
the mean values of Lýngdalur a and Thrasaborgir a; I b the mean
values of Lýngdalur b, Lækjamót a, and Arnarvatnsheiði a. II re-
presenls Lýngdalur d, Thrasaborgir b, Lækjamót b, Norðtunga a, and
Arnarvatnsheiði b and c. III, linally, represents the mean values
of Lýngdalur e, Thrasaborgir c, Norðtunga b, and Arnarvatnsheiði
d and e.
The distribution of species in the scale of snow-covering is as
the distribution of species in the scale of moisture. Some species
attain their maximum F.-percentage in class I, others in class II,
others again in class III. Some species have a high frequency per-
centage in one of the classes, others in two classes, either I and II
or II and III; only a small number of species occur with a high
frequency percentage in all classes.
A comparison betwreen the different scales of snow-covering
shows in what uniform proportions the species occur in the different
localities. It may be laid down as a main rule that the species
react uniformly to the same changes in respect of snow-covering.
A species which, in- one locality, attains its maximum F.-percentage
where there is a normal snow-covering but decreases if the snow-
covering changes no matter in what way, will behave in the same
'vay in all the other localities.