The Botany of Iceland - 01.12.1945, Blaðsíða 110

452
STEINDÓR STEINDÓRSSON
cords the Grimmia heath from Lyngdalsheiði at an altitude of c. 250-
400 m, here using the Icelandic name mosaþemba. The Grimmia heath
on Lyngdalsheiði exhibits a smaller number of species than the Grim-
mia heath described here, otherwise Molholm Hansen’s and my
results agree fairly well. I entirely subscribe to Molholm Hansen’s
view as to the distribution of the Grimmia heath in Iceland. This
formation is rare in the driest parts of northern Iceland; but where
the climate is more humid, it is always fairly widely distributed in the
highland as well as in the lowland. Thus I found it to be widely distrib-
uted on Melrakkasljetta (Steindórsson 1936), where it shows a greater
abundance of species than in the highland, but otherwise is a quite
similar formation.
The Grimmia heath is distributed within several of the northern
countries and has been described by different authors; thus from
Greenland (Kolderup Rosenvinge 1897, pp. 211-214), Jan
Mayen (Ostenfeld 1898), the Faroes (Ostenfeld 1906, p.
116) : “... on the higher-lying mountain plateaus (not below c. 400 m
above sea-level) if otherwise the conditions for its development are
present. The most important of these are: level or slightly sloping ter-
rain, not too great moisture of the soil, and fairly good shelter from
the gales” (translated from the Danish). This agrees wrell with the
conditions under which the Grimmia heath is found in the highland
of Iceland; I assume, however, that it may very well tolerate some
wind if it does not carry blown sand with it. From Bear Island S u m-
merhayes & Elton record a moss heath with dominant Rhacomi-
trium lanuginosum and the most important phanerogams Oxyria
digyna, Ranuncidus pygmaeus, Salix polaris, Saxifraga cernua, and
S. caespitosa (1923, p. 224). Tansley (1911) records a moss
heath from the Scottish highland. It seems to be very rare in
Scandinavia, though Du Rietz (1925, pp. 49-50) records it from
the northern part of the Norwegian west coast, but farther inland
Rhacomitrium hypnoides forms “nur kleine Polstern”. H. R e s v o 11
Holmsen (1921) mentions a Rhacomitrium lanuginosum moss
field, which never forms largc continuous areas, but the greater
number of the species recorded by Resvoll Holmsen from
grassy moss ficlds in eastern Norway (1920, p. 183) arc the samc
as are found in the Grimmia heath in Iceland. Molholm Hansen
(1. c. p. 43) assumes that „In Scandinavia the Grimmia heath seems
to have been replaced by the Lichen heath”, which is, no doubt, quite
correct. It is worth noting that the Scandinavian lichen heath and the