THE BRYOPHYTA OF ICELAND 625 



pages some examples of the rocky-flat vegetation will be given, it 

 is, however, only in NW., SW. and in a few dislricts of N. and E. 

 Iceland, that this vegetation has been somewhat closely investigated, 

 whilst the ^vhole of the interior high land is quite unknown as far 

 as bryology is concerned. 



1. South Iceland. Barkarstadr, dry stony flat at an alti- 

 tude of 350 metres: Scattered ciishions of Schistidium apocarpum v. 

 riifescens, Rhacomitriiim hypnoides, R. fasciculare, Dicranoiveisia cris- 

 pula and Andreæa petrophila. 



2. Gravelly flat on Esja, at an altitude of about 550 metres: 

 Moss carpet, partly torn up by the wind, composed of Hypnum 

 iincincdiim and Schistidium apocarpum, scattered in which occur 

 rocky-flat piants such as Silene acaulis and Saxifraga oppositifolia. 



3. Akureyri, rather dry gravelly flat, at an altitude of about 

 900 metres: Moss carpet composed of Rhacomitrium hypnoides, Hyp- 

 num uncinatum, Hylocomium proliferum, Camptothecium nitens, Aula- 

 comnium turgidum, Dicranum congestum, Didymodon rufus, Eurhyn- 

 chium diversifolium , Lophozia quinquedentata and L. quadriloba. 

 Flowering piants entirely absent. On a dry slope at an elevation 

 of about 770 metres there grew Lescuræa Breidleri, Brachythecium 

 glaciale, B. reflexum, Dicranum Starckei, Lophozia lycopodioides and 

 L. alpestris, and on damp gravelly flåts near the snow line there 

 grew Pohlia gracilis (abundantly), P. cucullata, P. commutata, Poly- 

 trichum sexangulare, Oncophorus virens, Dicranum Starckei, Lophozia 

 alpestris, L. ventricosa, L. quinquedentata, L. quadriloba, Pleuroclada 

 albescens and Anthelia Jurcdzkana. 



Salix herbacea-Sibbaldia Vegetation (Hel g i Jonsson, 

 1900, p. 33) occurs everywhere in damp depressions and on slopes 

 where the subsoil consists of a layer of clay. This vegetation has 

 ils main distribution from 300 — 400 metres to about 700 metres, 

 and here, close to the snow line, it is replaced by pure moss-com- 

 munities, in which Salix herbacea occurs but scantily and at last 

 disappears entirely. The moss community consists of a low, dense 

 carpet of mosses and liverworts, interwoven with creeping stems of 

 Salix herbacea, so that only the tips of the shoots prolrude above 

 the carpet. The most abundant constituent of this moss carpet is 

 usually a low-growing form of Hypnum uncinatum or of Dicranum 

 Starckei in association with Rhacomitrium canescens. Dicranum molle, 

 Conostomum boreale, Polytrichum sexangulare, Anthelia Juratzkana, 

 Pleuroclada albescens, species o( Lophozia, and sometimes other species. 



