576 



A. HESSELBO 



dium and Fossombronia which were growing here, the thermometer 

 showed as high a temperature as 34 on the surface of the ground. 

 On a slightly damp flat which was covered with a low -growing, 

 dense form of Climacium dendroides, the surface temperature of the 

 ground was 43. 



In the more low-lying tracts, where the ground was rather 

 damp, or partially inundated with hot water, there had, in several 

 places, developed a luxuriant vegetation of phanerogams and moss- 

 es, which was, however, often much trodden down. Here, in the 

 boggy parts, grew a low vegetation of Carex-Viola palustris, greatly 

 mixed with Bryophyta, of which the following species, which grew 

 intermixed, were observed: Hypnam stramineum , H. sarmentosum, 

 H.imponens, Hylocomium squarrosum , Sphagnum cymbifolium, Ca- 

 tharinea undulata, Calypogeia Trichomanis , Alicularia scalaris, Ha- 

 plozia crenulata, Scapania irrigua, Aneura pinguis and an undeter- 

 minable Pohlia. On damp clayey flats Archidium, Fossombronia 

 Dumortieri, Haplozia cremilata and Alicularia scalaris formed low, 

 dense mats in which Anthoceros punctatus occasionally occurred in 

 small rosettes. 



Below Great Geysir, Hypnum chrysophyllum grew on a clayey 

 flat inundated with tepid water. 



Laugarvatnshverir. By the shore of lake Laugarvatn, below 

 the farm of the same name and along the water's edge, there is 

 a row of springs containing boiling water saturated with sulphur- 

 etted hydrogen. The surrounding ground which consists of black 

 basalt gravel is, owing to its ex- 

 posed situation, quite bare of Bryo- 

 phyte vegetation ; and of higher 

 plants only a few specimens of 

 Polygonum Persicaria were found. 

 By the northernmost of the springs 

 only, which is situated at some dis- 

 tance from the lake shore, a warm, 

 damp clayey flat was covered with 

 a carpet of Sphagnum cymbifolium, 

 S. Girgensohnii, Polytrichum com- 

 mune, Hylocomium squarrosum, Hyp- 

 Fig. 24. Bryiim sp. , Older leaves deve- 



num stramineum, Archidium phas- loped beforelhcplant wasinundatedwith 



Coides, Pohlia grandiflora $, Aong- hot water ; b, leaves from shoot developed 



a 



a 



strcemia longipes, Gymnocolea inflata 



in hoi water (Geysir). 



