STUDIES ON THE VEGETATION OF ICELAND 101 
vegetation, and the Philonotis dy), rock pools and Grimmia heath. 
Since the Grimmia heath does not occur in North Iceland, this type 
may be left out of consideration, and of the remainder only the 
myri and the rocky pools are identical. Judging from the description, 
H. Jonsson’s fell-field comprises Stefansson’s melar, mo, and 
snow-patch, gravelly flats and screes corresponding to melar and mo, 
while the Anthelia crust and the Salix herbacea and Sibbaldia ve- 
getation must be regarded as snow patch vegetations. Thus for the 
highlands we get the following vegetation scheme which, in its main 
lines, is the same as on Lyngdalsheidi, viz. 1) melar (and, in addition, 
for South and East Iceland, Grimmia heath), 2) mo, 3) myri (in- 
cluding dy), and snow-patch (including the Salix herbacea and Sib- 
baldia vegetation and the Anthelia crust). In the following each 
of these types will be dealt with in more detail. 
As previously mentioned, the investigations to be described in 
the following were carried out on Arnarvatnsheidi. The latter forms 
part of the large plateau north-west of Langjökull which divides the 
Hüna Flöi area of valleys in the north from the Borgarfjöröur area 
of valleys to the south. The surface of the plateau consists of de- 
posits of the glacial period and appears as a landscape with count- 
less downs, depressions, and lakes. 
Of more conspicuous types of vegetation we find: melar, Betula 
nana mo, the knolly mo, jadar, myri and flöi, and geiri. The melar 
vegetation attains development at the top and on the ridges of 
the downs, occasionally some distance down the slopes. The Betula 
nana mo (or the level mo) occurs on large flats at high levels among 
tracts of melar. The mo (the knolly mo) occurs in small hollows 
in the Betula nana mo, along the slopes of the downs, in large flat 
depressions at high levels, and in the margins of the snow patches. 
Jadar occurs especially in the depressions between the downs and 
on the borders of the myrar, while the myri vegetation occurs 
in the larger and deeper depressions and around the lakes. The 
moister parts of the myri are occupied by the flöi. The geiri 
vegetation attains its finest development in large shovel-formed 
depressions in the hills, most frequently, though not so typically, 
developed along the slopes of the hills. 
As elsewhere in Iceland, the melar and geiri vegetations are 
dependent respectively on a slight and a deep snow-covering. The 
