The Botany of Iceland - 01.12.1930, Page 42

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H.M0LHOLM HANSEN
A 1 comprises such species as must be termed arctic though
they do not extend very far north in Greenland. Their northern
limit in West Greenland lies south of 66° N. In Iceland the species
are équally distributed through all altitude zones, though with a
slight maximum in the lowlands. The A 1 species occur most com-
monly north of the “jökull line”, especially in North Iceland.
III. Investigation of the distribution of the species, partly in
the North European and the adjacent arctic countries, and partly
in Iceland, gave the result that the 7 subgroups show a fairly smooth
gradation from A 3, which is adapted to the coldest conditions, to
E 1, which requires the greatest ainount of heat. The increasing
adaption to arctic conditions may, however, be demonstrated in
another way, too, viz. by a comparison of the individual groups
with respect to their content of Raunkiær’s life forms. If the groups
and subgroups express an increasing degree of adaption to the
arctic climate, this must appear by the fact that that group or those
groups which are best adapted to the arctic climate shows or show
the greatest content of arctic life forms and fewest temperate life
forms, whereas the reverse must be the case with the remaining
groups.
Against each species in the above list is given the life form of
the species in question, and in table 7 are stated the biological
spectra of the groups.
According to Raunkiær (1908, 1912), Ch is the life form which
is best adapted to the arctic climate, while H and G are indiíferent,
and Ph, HH, and Th are adapted to non-arctic conditions. Ry com-
parison of the biological spectra of the A and E groups with the
spectrum of the entire flora, it will be seen that the A group is
more arctic in character, the E group more temperate in character
than the flora as a whole. The subgroups under A and E bear the
same relation to their respective main groups as tliese to the whole
flora. The high HH percentage in E 4 and partly also in E 1 is
however, worth noting.
On reviewing the biological spectra of the various parts and
zones of Iceland we saw that the Ch % was lowest (15 °/o) in the
south country where the amount of warm water at tlie coasts was
greatest, that it then rose gradually as the amount of Polar water