664 A. HESSELBO 



The difference in the climate is also apparent from the faet 

 that species, which in North and East Iceland are common as far 

 (lown as the low land, in South Iceland are first met with in 

 abundance at a higher altitude. This is for instance the case with 

 Schistidinm riviilare, Oncophoriis Wahlenbergii, O. virens and Dicra- 

 niim congestiiin which are not common until at a height of 200 — 

 300 metres. The Bryophyte vegetation in the higher-lying bogs (200 

 — 500 metres) also corresponds closely with the bog vegetation of 

 the lowlands of North and East Iceland, while the bog vegeta- 

 tion of South Iceland ditfers somewhat considerably in character 

 (p. 561). 



North- west Iceland. The Bryophyte vegetation differs in 

 several points from that of the other districts. From a narrow belt 

 of coastal land the country rises abruptly to a height of about 500 

 metres, so that there is only room for the boggy tracts, so common 

 in the other districts of Iceland, in those valleys which, from the 

 head of the fjords, ascend towards the high land. Here the number 

 of species is essentially smaller than in the other districts of Ice- 

 land, since many of the common species, as well as of the rare 

 ones, are absent, on the other band, however, there are some few 

 species which are wideh' distributed in North-west Iceland, but are 

 absent from, or rarer in the other districts. This, among others, 

 is the case with regard to several of the species belonging to the 

 heath formation. 



Dicraimm fiiscescens, D. inajns and D. molle are very common 

 in NW. Iceland and, in association with other species (especially 

 Hepaticæ), form Dicramim heaths (p. 591): a formation which is 

 otherwise rare in Iceland. Pohlia imtans and Bryiim cirratum are 

 also common, especialh' in the birch coppices. Polytrichiim piliferum 

 is tolerably frequent and has been found in fruit in several piaces. 



Lophozia Flærkei is very common as far upwards as about 

 5(J0 metres above sea-level. It has, however, only been found in a 

 lava-field in SW. Iceland. 



There are also several hygrophilous species which are charac- 

 teristic of NW. Iceland: Sphagnum sqnarrosuni is frequent on damp 

 slopes and S. riparium is rather common in pools. On inundated 

 ground Scapania nliginosa, S. palndosa, Harpanthns Flotowianns and 

 Philoiwtis seriata are very common and often form — either sepa- 

 rately or collectively — the bulk of the vegetation. Hijpnum fluitans 

 var. falcatnm occurred abundantly north of Isafjordur. 



