A. HESSELBO 



Jnncus and Carex tufts, and this formation must most nearly be 

 termed a transitional form between moss-heath and meadow-land. 

 On the whole, Rhacomitrium canescens thrives best in Iceland on 

 somewhat damp ground, under quite similar conditions as Anla- 

 comnium turgid urn. 



The Mixed M o s s - h e a t h (Hylocomium - Rhacomitrium heath) 

 occurs especially on slightly inclined gravelly flats, under similar 

 conditions as the heather moor, and is, as a rule, a pioneer for 

 the latter. It may, however, also develop into a grass or herb 

 slope, where the ground is wetter. The chief species of this moss 

 carpet are Rhacomitrium canescens, R. hypnoides and species of 

 Hylocomium., but as a rule many other species are found intermixed 

 with these. 



In a moss-heath near Modruvellir (Esja), on a slightly inclined 

 gravelly flat, at an altitude of about 100 metres, the chief species 

 of the Bryophyte carpet w r ere Hylocomium proliferum, Rhacomitrium 

 hypnoides, R. canescens and Hypnum uncinatum; more scantily oc- 

 curred: Hylocomium loreum, H. squarrosum, Climacium dendroides, 

 Antitrichia curtipendula , Brachythecium albicans, Pohjtrichum alpi- 

 num, P. urnigeriim, Timmia austriaca, Pohlia cruda, Ditrichum flexi- 

 caule, Bartramia ilyphylla, Distichium montanum, Ptilidium ciliare, 

 Fmllania Tamarisci, Lophozia lycopodioides , L. quinquedentata and 

 L. quadriloba. Scattered in the Bryophyte carpet grew a few flower- 

 ing plants such as Anthoxanthum and Galium verum, and this 

 moss-heath will undoubtedly develop into grassland. 



On a flat interspersed with stones at an altitude of about 

 400 metres the Bryophyte carpet was composed of Rhacomitrium 

 hypnoides abundantly mixed with R. canescens, Hylocomium parie- 

 tinum , Hypnum uncinatum and Dicranum Starckei. As an inter- 

 mixture in the Bryophyte carpet occurred: Timmia austriaca, Pohlia 

 commutata, Distichium montanum, Lophozia quinquedentata, L. qua- 

 driloba., L. alf)estris, Plagiochila asplenioides , Blepharostoma tricho- 

 phyllum, Anthelia Juratzkana., Alicularia scalaris, Cephalozia pleni- 

 ccps and C. bicuspidata. Flowering plants were almost entirely 

 absent. 



On prominent knolls of earth occurring on heathland and 

 grassland, on dry ledges and slopes, a very peculiar Bryphyte 

 covering is often found: low, very compact cushions of Diphyscium 

 sessile in connection with several liverworts, especially Gymnomi- 

 trium concinnatum, arc found covering the soil with a very dense 



