THE BRYOI'HYTA OF ICELAND 549 



appears to prefer smaller rivers with large loose blocks of rock al 

 the bottom. 



Several other Bryophyta occur either mixed with the above or 

 occasionally as dominants in the Bryophyte vegetation. Schistidium 

 rivnlare is very common and often occurs abundantly. Hypnnm 

 dilatatum, H. alpinum and H. alpestre are common in the northern 

 and eastern parts of the country, but are absent from or are rare in 

 other parts. In the river Ellidara near Reykjavik the bottom was 

 in several places covered with Fontinalis androgyna. In shallower 

 water, and especially on inundated rock- surfaces in waterfalls, 

 several other species also occur. Almost everywhere in such localities 

 are found: Haplozia cordifolia, Scapania undulata, Brachythecium 

 rivnlare, Rhynchostegium rnsciforme , Hypnnm pcdustre, H. falcatnm, 

 Philonotis fontana, Mniobnjnm albicans var. glacialis, Brynm Diwalii 

 and Brynm ventricosum together with some of the species which 

 thrive best in places where they are outside the water during a part 

 of the year. 



Siones and rocks which protrude above the surface of the 

 water and are inundated only during specially high water-levels 

 are usually covered with a dense moss-carpet consisting of nume- 

 rous species. In addition to the majority of the species of river- 

 bottoms there occurs also an abundance of those belonging to damp 

 rocks. Among the species which are rarely absent from such lo- 

 calities may be mentioned: Hypnum falcatnm, H. filicinnm , Schisti- 

 dium riuulare, S. gracile, Rhacomitrium aciculare, R. sudeticum, Blindia 

 acuta, Dichodontium pellucidum, Amphidinm Mougeottii, Haplozia 

 atrouirens and Mnium pnnctatnm., and in North and East Iceland, in 

 addition to the above-mentioned, Philonotis seriata and Hypnum 

 decipiens are to be found. A somewhat different vegetation occurred 

 in the river Rekyirdalsa in SW. Iceland, which is so well supplied 

 from hot springs that in the beginning of June the water had a 

 temperature of about 12, while that of the streams flowing into 

 it on both sides was only 4 5. Hypnnm ochraceum, which is else- 

 where so common, was entirely absent, and Schistidium rivnlare 



*j 



occurred very scantily. On rock-surfaces and larger stones Hypnnm 

 palustre, Brachythecinm riuulare and Rhynchostegium rnsciforme grew 

 abundantly, the last had also set fruit. Fontinalis longifolia covered 

 the bottom in many places, and on stones protruding above the 

 surface of the water Hypnum filicinnm and Schistidium gracile were 

 growing. In the cold tributary streams the usual vegetation occur- 



