The Botany of Iceland - 01.12.1942, Side 43

THE PTERIDOPHYTA AND SPERMATOPHYTA OF ICELAND
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The Snow-line.
Thoroddsen (1911, p. 1—68) has given a comprehensive descrip-
tion of the Icelandic glaciers, and his work is fundamental for our
present knowledge of the topography and distribution of glaciers in this
country. Partly on the basis of Thoroddsen’s data Eythorsson has (1931,
p. 11) constructed a map showing the height of the firn-limit in dif-
ferent parts of the country. Eythorsson calls attention to the fact that
the firn-limit is absolutely lowest near the western coast of Húnaflói
(400 m above sea-level) where the summer temperature is comparatively
low, and humid north-easterly winds are frequent. In the southern part
of Vestfirðir the snow-line lies at about 400 m s. m., on the Snæfellsnes.
peninsula at 800—1000 m s. m., and in Austfirðir (E. Iceland) at
900—1000 m s. m. Near the south coast the firn-limit is fairly constant
between 900 and 1000 m s. m., and it attains its greatest height on the
highland to the north of Vatnajökull, in Fjallasveit, about 1600 m s. m.
In the latter region some mountain-massives rise up to 1000 metres.
without any glaciation, and summits 1000 metres high show only small
traces of glaciation. Approaching the north-eastern coast we again find
some glaciation, or at least large perennial fimfields between 800 and
1000 m s. m.
Like the snow-line, the level at which the glacier-tongues end also
differs greatly. Thus in Vestfirðir the glacier-tongues of Drángajökull
descend to about 25 m above sea-level, and in S. Iceland Vatnajökull
sends glacier-tongues down to about 9 metres above sea-level.
The Main Types of Vegetation in Iceland.
In several of the previous works on the Icelandic Flora attempts
have been made to classify the vegetation in a series of types (Gron-
lund 1877 and 1884, Stefán Stefánsson 1895, Helgi Jónsson 1895 b,
1900 and 1913, C. H. Ostenfeld 1899 and 1905, Th. Thoroddsen 1914,
Ingimar Óskarsson 1927, and Molholm Hansen 1930).
Thoroddsen, loc. cit., p. 317—343, gives a general view of the chief
plant-formations or types of vegetation occurring in Iceland, and for
each type adds a discussion of its special floristic features. Thoroddsen
sets up 14 different types of vegetation, mostly adopting Helgi Jónsson’s
divisions (cp. H.J., loc. cit.).