The Botany of Iceland - 01.12.1945, Blaðsíða 120

462
STEINDÓR STEINDÓRSSON
almost devoid of vegetation. Often fissure systems forming polygons
occur in the melur, and some of these polygon flats may cover several
square metres. Altogether the melur is formed in the most exposed
places, but may extend for several miles, in depressions as well as on
hills.
The vegetation of the melur is always very scattered, and often it
is almost absent, so that the melur is a complete desert; however, it
is rarely as barren as the areas of blown sand. The travelling reports
speaking of the entirely barren melur deserts devoid of vegetation in
the interior of Iceland should rarely be taken too literally, for often
we find there, perhaps at intervals of several scores of metres, perhaps
of a hundred metres, small and insignificant plant individuals which
brave the unfavourable conditions afforded by the melur. As a rule
the plants form small tufts, and grow preferably in the lee of stone
blocks or in the small depressions formed along the polygon cracks.
The biggest stones of the melur have often accumulated along these
cracks, and as they give even more shelter, the plants are gathered
around them. The main vegetation consists of phanerogams, but mos-
ses occur also, and occasionally the lichen Stereocaulon denucLalum
dominates, forming grey vaulted cushions. The plants always form
small tufts, which are often destroyed on the side whence the wind
constantly blows (cf. Samuelsson 1917,pp. 129-136). The phen-
omena described by him are very often found on the melur in the
highland of Iceland.
The phanerogams most frequently found on the melur are: Silene
acaulis, Armeria vulgaris, Arabis petraea, Cerastium alpinum, Saxi-
fraga oppositifolia, Salix herbacea, and Poa glauca); furthermore,
especially where the melur is more sandy, Arenaria norvegica, Festuca
rubra, Silene maritima, and Carex incurva. The melur is described by
several authors, and the main features will be mentioned here. Thus
Stefánsson (1894, p. 195) describes the melur vegetation on the
mountains near Vatnsdalur as a vegetation “in which the plants occur
singly with large bare intervals” (translated from the Danish). The
plant list given by him (p. 195) comprises a greater number of species
than found on the most exposed highland melur, but on the other
hand it is in good agreement with my circling results; however, all my
analyses were made near oases, so they convey no impression of the
poorest melur vegetation. The same is the case with Stefánsson’s
description of the melur on Vatnsdalsháls (1. c. p. 199 et seq.), where
he also describes the influence of the wind on the mode of growth of