The Botany of Iceland - 01.12.1930, Side 190

180
H. M0LHOLM HANSEN
maximum development in jaðar. Ch are of slight importance, while
the number of G is on the increase.
The valllendi vegetation is a variant developed on the cones
deposited by the streamlets of melting snow. There is no knoll
formation and the vegetation is that of a more southern environment.
The flag vegetation. The surface is a bare clayey flat with
scattered knolls and stones. The vegetation is characterised by its
high therophyte percentage, though in jaðar, too, Th attain a relative
though small maximum. Arctic species are more dominant in flag
tlian in jaðar or especially valllendi. The jaðar vegetation seems
to be confined to the Icelandic lowlands, to the jaðar or the trans-
ition from mo to mýri.
The mýri vegetation is peculiar to moist soil which must
not, however, be covered with water all the year round. The surface
is knolly. Here the vegetation likewise consists of an equal mixture
of arctic and southern plants, but the most arctic and the most
southerly either do not occur or their number is much reduced
compared with that of mo and jaðar. G are the dominant life-form,
Ch attain a relative maximum, while the number of H is much
diminished. The number and density of the species are appreciably
less tlian in mo and jaðar.
The types of mýri occurring in Iceland are as follows.
Fór mýri, which develops in depressions with stagnant water.
Halla mýri, which develops in places where the ground water
comes to the surface, thus especially at the foot of mountains.
Fét mýri, which occurs near running water, along the banks
of rivers, near tlie sea etc.
The flói vegetation develops where the soil is constantly
covered with water all the year round. The surface is level, without
knolls. The vegetation is very scattered and poor in species and
consists almost exclusively of southern plants. The dominant life-
form is G. The hydrophytes or helophytes likewise attain their
maximum development in the flói.
The geiri vegetation is confmed to soil with a constant and
deep snow-covering from early autumn to late spring. The surface
is always level, without knolls. The vegetation consists principally
of southern plants, notably those requiring the highest temperature
which are found in greatest quantity here. The dominant life-foi'm
is H, of less importance are Ch and especially G. Both the number
and density of species are relatively high, though less than in the mo.