(564 A. HESSELBO 



The difference in the climate is also apparent from the fact 

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

 down 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 rivulare, Oncophorus Wahlenbergii, 0. virens and Dicra- 

 nnm congestnm 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 differs somewhat considerably in character 

 (p. -)61). 



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 hand, however, there are some few 7 

 species which are widely 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. 



Dicramim fuscescens, D. majus and D. molle are very common 

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

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

 otherwise rare in Iceland. Pohlia nntans and Bryum cirratum are 

 also common, especially in the birch coppices. Polytrichum piliferum 

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



Lophozia Flcerkei is very common as far upwards as about 

 5(J() 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 squarrosum is frequent on damp 

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

 ground Scapania nliginosa, S. paludosa, Harpanthns Flotowianus and 

 Philonotis seriata are very common and often form either sepa- 

 rately or collectively the bulk of the vegetation. Hypnnm fluitans 

 var. falcatum occurred abundantly north of Isafjordur. 



