20 H. MØLHOLM HANSEN 
gree that no satisfactory 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 determine 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 into 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 them. 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 first, and group 2 occupies an intermediate 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 
occurring farthest south. The Icelandic flora is thus divided into 
7 groups according to the distribution of the species and more pre- 
cisely according to their “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 be 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. 
