The Botany of Iceland - 01.12.1930, Page 30
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H. M0LHOLM HANSEN
gree that no satisfaetory result was obtainable. I had then no other
alternative but to attempt a classification myself. In working out
this, an acquaintance with the groups of other authors has of course
been of great use to me.
The best way would no doubt be to delermine the course of
the Ch biochores in the arctic regions and in Europe and next to
determine between which biochores the individual Icelandic species
most frequently occur, and then classify the flora on the basis of
these data. This work I began but had to give it up again as it took
so much time that I dared not at the present juncture embark upon it.
The principles which I then adopted, and on which the clas-
sification of the flora given below is based, are the following. First
I divided the flora inlo two larger groups A and E, according as
the species were of common occurrence in arctic and subarctic
regions but were absent or rare in temperate zones (group A), or
the species were common in or typical of the more southerly regions
(group E). The A group corresponds approximately to the “arctic
species”, “alpine species”, “mountain plants” etc. of the various
authors, while the E group corresponds to the “British species”,
“European species”, “Northern species”, “Southern species”, “Low-
land species” etc. The distinction between these two groups does
not cause any difficulties, these do not appear until we attempt to
subdivide thein. In the following the A group is subdivided into
three minor groups according to the northern limits of the species,
or their ability to withstand cold, in such a way that group 3 ex-
tends farthest north or highest up the mountains while group 1
stops íirst, and group 2 occupies an interinediate position. On the
same principle group E is subdivided into 4 minor groups, group 4
including the species occurring farthest north and group 1 those
oecurring farthest south. The Icelandic flora is thus divided into
7 groups according to the distribution of the species and more pre-
cisely according to tlieir “temperature demands”.
The distribution of the species has been investigated in the
following countries: — Ellesmereland, North Greenland, Spitsbergen,
West and East Greenland, Iceland, the Faeroes, Norway, Sweden,
Finland, Novaia Zemlia, Ireland, Scotland, England, Denmark, the
Baltic States, and north-eastern Germany. The works on the re-
spective floras will he found in the bibliography. — In fig. 1 tempe-
rature curves for a series of stations along the western coasts of
Greenland and Scandinavia are shown.