624 A. HESSELBO 



On somewhat damper gravelly ground, especially where large 

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

 comes richer, so that liere we sonielimes find 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 foUowing species: Hyloconiiiim 

 proliferum, Hypniim iincinaium, Brachythecium reflexum, Lesciiræa 

 Breidleri, Rhacomitrium hypnoides, R. fasciculare, R. sudeticum, R. 

 canescens, Schistidium apocarpum, S. gracile, Bryiim ventricosiuu, Pohlia 

 commiitata, P. cuciillala, P. gracilis, Pliilonotis fontana, Conostomum 

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

 trichiim sexangnlare, Oligotrichum hercynicnm, Lophozia alpestris, L. 

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

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

 Jiiratzkana and Gymnomitriiun concinnatum besides some rare or 

 more casual species, for instance Enrhynchiuni diversifolium, Brachy- 

 thecium glaciale, Aulacomniniii tiirgidinn, Bryiiin elegans, Bartramia 

 ityphylla, Pohlia Lndwigii, Didymodon rnhellus, I), riifiis, Desmatodon 

 latifolius, Distichium montanum, etc. Usually several species grow 

 intermixed, bul 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 flåts. Flowering 

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

 spp. and Stereocaulon condensatum) may occur abundantly in this 

 moss carpet. In the more low-ljdng 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. Lescurcca Breidleri is a com- 

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

 the most abundant constituent of the vegetation on stony slopes. 

 Conostomum boreale is also common, especially in NW. Iceland 

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

 vening spaces between the stones are filled up with its compact 

 tufts. Brachythecium glaciale 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 w^ater is drained 

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

 covered with Mniobryum albicans var. glacialis, and in damp spots 

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

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



