STUDIES ON THE VEGETATION OF ICELAND 11 
the difference between the coldest and the warmest months is thus 
great, 17.2° C. The precipitation is slight and storms are frequent. 
To this must further be added a probably very thick and at any 
rate constant covering of snow in winter. 
Of interest in connection with plant geography is further the 
situation of the jökulls and the snow-line. We have previously seen 
that most of the jökulls gather along a line connecting the two places 
where the waters of the Gulf Stream and the polar water meet, 
respectively to the south-east and the north-west of Iceland. The 
line begins with the large Vatnajékull on the south-east and extends 
north-westwards over Tungnafellsjökull, Hofsjökull, Langjökull, and 
Eiriksjökull until it terminates in Gläma and Drangajökull in Vest- 
firdir. To the north of the range of jökulls there are only a few 
small jökulls on the peninsula between the Eyja- and Skagafjördur 
while to the south we have the large Myrdalsjökull and some smaller 
ones, more especially Snefellsj6kull. 
The area of the jökulls is largest towards the cold, humid, and 
foggy eastern regions and decreases strongly towards the north-west. 
The area of Vatnajökull is about 8000 km”; of Hofsjökull about 
1350 km?, of Langjökull 1300 km”, of Glama about 60 km”, and 
of Drangajökull 350 km”. Vatnajékull’s greatest altitude above sea 
level is 2119 m., that of Hofsjökull 1700 m., of Langjökull 1400 m., 
of Glama and Drangajökull about 900 m. 
The snow-line lies at very different altitudes, coming down lowest 
on the south side, while on the north side it lies somewhat higher, 
the east and west sides occupying an intermediate position. On 
Vatnajökull the snow-line on the north side lies at a height of 
1300 m., on the north side of Hofsjökull at 1200 m., and on the 
north side of Langjökull at a height of 1100 m. On the south side 
the snow-line lies at a level of 900 m. In Vestfirdir the height of 
the snow-line above the sea is 400—650 m. On Myrdalsjékull the 
snow-line lies at a height of 1100 m. on the north side, and 800— 
900 m. on the south side. 
Below the snow-line proper comes a zone with snow-drifts 
which either never melt, the permanent snow-drifts, or only 
melt in very hot summers, the variable snow-drifts. It is 
difficult to set any lower limit to these two zones. On Arnarvatns- 
heidi north-east of Langjökull, where the snow-line lies at a height 
