The Botany of Iceland - 01.12.1930, Page 52

42
H. M0LHOLM HANSEN
in the moss. Other species met with are especially Carex rigida,
Polygonum viviparum, Silene acaulis, Armeria and Empetrnm. Pro-
ceeding still higher, Salix herbacea is the only more conspicuous
phanerogam in the moss carpet.
At its lower limit tlie mosathembur vegetation passes over into
the Elyna mo.
Above we have described the appearance and composition of
the mosathembur vegetation on Lýngdalsheiði. If we enquire into
its occurrence in other parts of Iceland, we find it described by
Helgi Jónsson for East Iceland (1895, p. 70), for South Iceland
(1905, pp. 40—42), and for Snæfellsnes (1900, p. 68 and p. 85). It is
most abundantly developed in East Iceland where it covers large
stretches of the mountain slopes in several of the fiords, and it is
particularly well developed at high levels. In South and South-West
Iceland it does not occur so plentifully, and apart from the lava
fields, covers only small areas. Its appearance and composition, how-
ever, are in close agreement in the various localities and correspond
to what was given above for Lýngdalsheiði.
In North Iceland and the highland tracts the mosathembur does
not seem to occur as a stable typical vegetation. Ostenfeld does
not refer to it in “Skildringer af Vegetalionen i Island” III—IV
(1905) either from Vestfirðir or from Melrakkasljetta. Personally I
have looked for it in vain in Húna Flói, in the highlands at Arnar-
vatnsheiði, and on Holtavörðuheiði. Typical mosathembur was not
seen in any of these localities; it had been replaced by the melar
vegetation.
The moss mo observed by St. Stefánsson on Grimstungnaheiði
which “should most probably be understood as a transitional form
between heather mo and pond vegetation”, the surface being uneven,
more or less tufted, and the soil moist, at any rate in the first part
of the summer, must not be confused with the mosathembur vege-
tation wliich only occurs on the relatively dry stretches. Thus,
the mosathembur vegetation in Iceland seems to be pe-
culiar to the higher levels of the rainy and foggy east,
south, and south-west country, that is to say, tlie coun-
try south of the jökull line. North of this line, where the cli-
mate is more continental, it does not occur as the typical vegetation,
being replaced by the melar vegetation here.
If we enquire into its distribution in the surrounding countries,
wæ find it developed botli to the north and to the south. Kolderup