Rit (Vísindafélag Íslendinga) - 01.06.1939, Síða 19

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distribution of Ch and the arctic plants, i.e. they are some-
what commoner in the lava, and this is easily understood
when we consider that the lava peat formation is compara-
tively young and has not formed a set association of plants.
The close relationship to the gravels is apparent, and they,
as was mentioned above, are scattered among the lava.
Formerly for instance Dryas octapetala L. was very wide
spread in the lava, but in the last 5—10 years it has
entirely disappeared. It is not unlikely that other gravel
formation plants that formerly grew in the lava dis-
appeared in this manner, though nothing is known for
certain about this. Also individuals from the neighbouring
plant formations will always be appearing as the condi-
tions in the lava change. A clear proof of this can be seen
in the northernmost part of the lava where Galium verum
L., Linum catharticum L., Brunella vulgaris L., and Sagina
procumbens L. are gaining a greater and greater spread,
and where the vegetation is most continuous. Here, there-
fore the climate and life-forms are at work to form on the
groundwork of the lava those life-forms which correspond
to the climatic and geographical position of the area.
There is in this country no material for comparison
with the lava formation but for the true peat formation
there are observations from Lækjamót, A = 61.5 and Ch
= 28.9 and from Björk, A = 42.7, Ch = 31.3 cf. M.H.
1930, p. 83. Now Lækjamót is in the north but Björk in
the south of the country and the average temperature,
summer temperature, winter temperature and annual
temperature rise in the south and are highest in the West-
mann Islands (cf. Climate, p. 10). Here we can clearly see
that the A group of species is a better reagent to the
climate, i.e. stands in inverse ratio to the rainfall and
temperature, Ch seems on the other hand to react better
to the soil, though there is a limit to the variations of
temperature it will stand.
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