624 A. HESSELBO 



On somewhat damper gravelly ground, especially where large 

 blocks lie scattered and afford shelter, the Bryophyte vegetation be- 

 comes richer, so that here we sometimes tind a continuous carpet 

 of mosses and liverworts, through which the tops of the stones 

 protrude. This carpet of mosses and liverworts is usually composed 

 of a larger or smaller number of the following species: Hylocomium 

 proliferum, Hypnum uncinatum, Rrachythecium reflexum, Lescarcea 

 Breidleri, Rhacomitrium hypnoides, R. fascicnlare, R. sudeticum, R. 

 canescens, Schistidium apocarpum, S. gracile, Rryum ventricosum, Pohlia 

 commutata, P. cucnllala, P. graciliSj Philonotis fontana, Conostomum 

 boreale, Dicranum Blyttii, D. molle, D. Starckei, D. congestum, Poly- 

 trichum sexangulare, Oligotrichum hercynicum, Lophozia alpestris, L. 

 quinquedentata, L. ventricosa, L. lycopodioides, L. Floerckei, L. quadri- 

 loba, Alicularia scalaris, A. geoscypha, Pleuroclada albescens, Anthelia 

 Juratzkana and Gymnomitrium concinnatum besides some rare or 

 more casual species, for instance Eiirhynchium diver si folium, Rrachy- 

 thecium glaciate, Aulacomnium turgidum, Rryum elegans, Bartramia 

 ityphylla, Pohlia Ludivigii, Didymodon rnbellus, D. rufus, Desmatodon 

 latifolius, Distichium montanum, etc. Usually several species grow 

 intermixed, but the moss carpet may also be formed by a single 

 species or a few. At elevations above 500 600 metres Rhacomitrium 

 sudeticum often forms extensive growths on gravelly flats. Flowering 

 plants are entirely absent, but lichens (Cetraria islandica, Cladonia 

 spp. and Stereocaulon condensatum) may occur abundantly in this 

 moss carpet. In the more low-lying parts of the rocky flat Rha- 

 comitrium sudeticum rarely occurs abundantly, but is replaced by 

 Schistidium gracile and Schistidium apocarpum, which form low, 

 blackish-brown or reddish-brown mats. Lescuraa Breidleri is a com- 

 mon species, especially in NW. Iceland, where it is in many places 

 the most abundant constituent of the vegetation on stony slopes. 

 Couostomum boreale is also common, especially in NW. Iceland 

 where, on the dry gravelly flats of the mountain heights, the inter- 

 vening spaces between the stones are filled up with its compact 

 tufts. Rrachythecium glaciate in company with Hypnum stramineum 

 covered the damp areas of the rocky flat near Isafjordur, at a height 

 of 450 500 metres. In the channels, in which the water is drained 

 away during the melting of the snow, the stones are often entirely 

 covered with Muiobryum albicaus var. glacialis, and in damp spots 

 and near springs Phitonotis fontana forms light-green cushions, as 

 it does near the "Dy" in the more low-lying tracts. In the following 



