636 A. HESSELBO 



cording to Thorodd se n's statement, the birch coppices ascend to 

 550 metres. In North-west Iceland the birch coppices in D^rafjordur 

 ascend to about 270 metres, and around Isafjardardjup probably 

 not very far above 200 metres. In South Iceland the upper limit 

 of the heather moor generally lies at an altilude of 300 — 350 metres, 

 but in sheltered valleys both birch coppices and heather moor may 

 be met with at an attitude of above 500 metres. On the whole, 

 the upper limit of the heather moor may, however, be reckoned to 

 lie, on an avcrage, at an attitude of about 300 — 350 metres. 



All that is situated above this limit is in the following designa- 

 ted the Alpine region, since the willow region \vhich occurs in the 

 mountains of Scandinavia and Central Europe is not tj'pically de- 

 veloped in Iceland"; not, at any rate, in the coastal districts. The 

 reason for this must in a great measure be sought in the geological 

 structure of the country. The gradually-ascending or terrace-formed 

 land near to the coast rises to a height of 200-300 metres, and 

 from liere the mountains almost everj'where shoot abruptly upwards 

 to a height of 600 — 700 metres, right up to the plateau on the 

 mountain summit, from which again a few peaks or rock-masses 

 protrude. This leaves very little room for vegetation between 300 and 

 600 metres, with the exception of the valleys, which are, as a rule, 

 very narrow. This is very decidedly noticeable in North-west and 

 East Iceland, where almost everywhere along the coasts, from a 

 quite narrow coast-land, the mountains rise abruptly to an almost 

 constant height of (500 metres, so that only at the head of the val- 

 lej's do terraces occur at various levels as far upwards as the 

 mountain heights. In Norlh Iceland, especially towards the east, 

 the country rises more gradually up towards the interior high land, 

 and there — at any rate somewhat inland — willow coppices and 

 willow swamps occur also, but their Bryophyte vegetation has been 

 very little investigated. 



Taking the above as a basis the vegetation may be classified 

 into zones, according to attitude. 



A. The Lo w land region which reaches to the upper limit of 

 the heather moor and the birch. 



B. The Mountain region which includes slopes and flåts to 

 a height of about 600 metres. 



C. x\lpine Heights (the Snow region) to which is reckoned 

 all that is situated higher than about 600—700 melres. The 

 vegetation there is very poor in species, and is strongly atTected 



