The Botany of Iceland - 01.12.1914, Page 147

PHYSICAL GEOGRAPHY
331
with blown sand. Where the sand-covered tracts reach the shore
their outermost border supports a halophilous vegetation which, at
a short distance from the coast, is replaced by the common plants of
sandy soil and rocky flats. On gravelly tracts of sand in the low
lands the following plants are the commonest: Silene maritima, Ar-
meria maritima, Festuca rubra, v. arenaria, Carex incnrva, Agrostis
alba, Juncns balticns, Elymus arenarius and Potentilla anserina; also
Galium verum and Thymus serpyllum, often occurring in patches.
Although the vast stretches of glacial sand in South Iceland have
a fairly variable surface yet they are extremely poor in plant-life;
owing to “glacier-bursts,” and to glacier-rivers constantly causing
floods and changing their courses, the vegetation has rarely the chance
of development. On Skeidarársandur (cf. H. Jónsson, 1905, pp. 20—22)
the following plants occur widely scattered: Chamœnerium lalifolium,
Arabis petrœa, Silene maritima, Saxifraga oppositifolia, S. cœspitosa
and Poa glanca, also small patches of Grimmia hypnoides; but there
are, in addition, large stretches quite naked and entirely destitute
of plant-life. The main part of Myrdalsandur is a desert almost
devoid of vegetation; far apart occur a few specimens ol' Arabis
petrœa, Silene maritima and Elymus arenarius; usually there is no
vestige of plant-life, and one may ride for hours without seeing a
single plant. In a few localities in Breidamerkursandur and Skei-
darársandur there is open grass-vegetation in small oases wliere the
sandy gravel from some cause or another lias for sorne length of
time escaped inundation by the ice-cold glacier water; in such
ptaces, in addition to Chamœnerium latifolium there occurs usually
Agrostis alba, Poa alpina, P. glauca, Aira alpitia, Calamagrostis stricta,
Festuca ovina, F. rubra v. arenaria, Carex incurva, Juncus balticus,
J. Iriglumis, Luzula spicata, Salix lanata, Oxyria digyna and others.
As may be seen, there is nothing specially characteristic in the
vegetation of these tracts of glacial sand and if they were rescued
from the destructive eflect of the glacier-rivers, they would quickly
becoine covered by the various plant-formations of the level country;
\ve have already mentioned one such instance, when Brunasandur
in 1783 was rescued from the inundations ot glacier-rivers bv a
lava-stream, which pushed a large river aside.
Blown sand supports a somewhat more peculiar flora, the
characteristic plant being Elymus arenarius-, but where it is very
mobile, as e. g. on the plateau in the neighbourhood of Fiskivötn
and between Tungná and Skaftá, no plant-life can thrive on it.
I'he Iiotnny of Iceland. I. 22