180 H. MØLHOLM HANSEN 
maximum development in jadar. 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 jadar, too, Th attain a relative 
though small maximum. Årctic species are more dominant in flag 
than in jadar or especially valllendi. The jadar vegetation seems 
to be confined to the Icelandic lowlands, to the jadar or the trans- 
ition from mo to myri. 
The myri 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 jadar. 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 than in mo and jadar. 
The types of myri occurring in Iceland are as follows. 
För myri, which develops in depressions with stagnant water. 
Halla myri, which develops in places where the ground water 
comes to the surface, thus especially at the foot of mountains. 
Fét myri, which occurs near running water, along the banks 
of rivers, near the sea etc. 
The flöi 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 flöi. 
The geiri vegetation is confined 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-form 
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. 
