THE BHYOPHYTA OF ICELAND 643 



albescens, Scapania remota, Ditrichum nwale, Pohlia polymorpha, P. 

 Liidwigii and Brachijthecium glaciale) have not been found below 

 tlie upper limit of the birch. 



In the Mountain region the number of species is as foUows: — 



42 Hepaticæ 



5 Sphagna 



134 Musci veri 



181 Total species. 



Of these, however, 10 Hepaticæ and 31 Musci veri have been 

 found only in the lowest part, at the boundary towards the Low- 

 land region, whereby the number of species \vhich in realitj^ be- 

 long to the Mountain region, is reduced to 140. Of these, 2 He- 

 paticæ, viz. Gymuomitriiim varians and Scapania remota and 3 Musci 

 veri, viz. Ditrichum nivale, Pohlia polymorpha and P. Ludwigii have 

 been found only in this region. 



In the Snow region the number of species is as follows: — 

 16 Hepaticæ, 42 Musci veri, total 58, of which, 6 Hepaticæ and 10 

 Musci have been found only in a few localities and cannot be re- 

 garded as belonging to this region. In all, 42 species remain, of 

 which, however, only 8 Hepaticæ and 20 Musci veri are fairly fre- 

 quent, while the others have been found only in a few localities. 

 The majority of the species belong to those which are of equal 

 frequency at all attitudes, and only 4 species (Plenroclada albescens, 

 Dicranum falcatum, Pohlia cucullata and Polytrichnm sexangulare) 

 can be designated true Snow'-region species. 



The number of species decreases rapidly as the height above 

 sea-level increases, and even at the upper limit of the heather moor 

 the number falls to about 40 % of the total number of species. 

 Above a height of about 600 metres the number scarcely reaches 

 15 % of all the species. 



