The Botany of Iceland - 01.12.1914, Síða 148

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THORODDSEN
Where the sand becomes more stable, or there is shelter, Elymus
arenarius appears, often associated with Festuca rubra v. arenaria;
not until the sand becomes somewhat fixed do other species appear,
e. g. Juncus balticus, Carex incurva, Agrostis alba, Festuca ovina,
Silene maritima, Salix lanata, S. glauca and occasionally Halianthus
peploides in localities not too far away from the coast. Extensive
Fig. 32. Salix lancita and, in the background, Betula odorata growing in black blown-sand
(volcanic asli) near Jökulsá, betwccn 'As and Svinadal; July, 1909.
(Phot. A. Hesselbo.)
tracts are covered with different Salices, especially in Fjallasveit,
where in some places on sandy flats Carex incurva also occurs in
abundance; moreover, in Myvatnsöræfi, Sudurárbotnar, Rangárvellir,
and several other places. Where the soil is broken up and re-
moved by sand-storms as deep down as to the underlying gravel,
as in several places in the southern lowlands in the neigbourhood
of Hekla, small tufts of Festuca rubra and F. ovina are the first to
appear, then come Juncus balticns, Equisetum arvense, Agrostis alba,
Silene maritima, Salix lanata and S. glauca-, then gradually several
species of grasses make their appearance until at last a grassy wil-
low-flat is formed which makes an excellent sheep pasture. Here
and there on the plateau are damp flats of old blown-sand inter-