110 H. MØLHOLM HANSEN 
loped it is easily distinguished from the other types of vegetation 
by the very large knolls of which the surface consists. These often 
attain a height of 1 m. or more and 1 or several m in diameter. 
The distance between the individual knolls is up to 1/> m. The 
jadar vegetation belongs to moderately damp soil having a normal 
snow-covering in the winter. The composition of the vegetation 
can be shown to differ somewhat in the different localities, and 
possibly several types of highland jadar may with good reason be 
established in the future, according to the degree and kind of moi- 
sture of the soil, and the amount of shelter provided by the snow- 
covering. 
On an average, the density of species was c. 12, the number of 
species 35, in the jadar localities examined by me. Ch have become 
much less dominant, the Ch percentage is only 20.5 and attains a 
relative minimum with this value, whereas the H percentage attains 
its maximum here, the average H percentage being 51.3. The G 
percentage which has risen steadily has reached a value of 27; it 
is noteworthy that the Th percentage attains a relative maximum 
of 1.5 in the jadar vegetation. 
The peculiarities to be noted in the species group spectrum are 
a diminution of the A percentage due in the main to a diminution 
of the A 3 percentage, a slight rise in the E 3 percentage, and the 
appearance of E 2 species in a quantity of 3.3 per cent. 
The more conspicuous chamaephytes are Empetrum nigrum and 
the Salix species Salix herbacea, glauca, and phylicifolia; Salix 
phylicifolia is the characteristic dominant for jadar. In more scat- 
tered growth there occur Vaccinium uliginosum, Silene acaulis, Armeria 
vulgaris, and Cerastium alpinum. For the rest it is H and G which 
characterise the vegetation, notably Carex rigida, and in addition, 
on the wettest soil, Deschampsia alpina. The more prominent species 
are Polygonum viviparum, Thalictrum alpinum, Luzula spicata, Carex 
rigida, Equisetum arvense, E. variegatum, Festuca rubra, F. ovina, 
Deschampsia alpina, Poa alpina, Rumex acetosa, Galium Normanni, 
Cardamine pratensis, Taraxacum officinale, Potentilla verna, Poa pra- 
tensis, Calamagrostis neglecta, Viola palustris, and Saxifraga Hirculus. 
A number of these species are characteristic of the jadar. 
A couple of types which I had not time to examine more 
closely shall be briefly mentioned here. One is the moss mo which 
St. Stefansson has described from Grimstungnaheidi (1894, p. 201 
(cf. p. 10)). This type of vegetation was also found on Arnarvatns- 
