582 A. HESSELBO 



Where the surroundings of the spring consist of siliceous sinter, 

 as is the case with the majority of the springs of the Geysir-com- 

 plex, and in Reykirdalur, all species of Sphagnum are absent, or 

 are to be found only as a subordinate component, and the moss 

 vegetation is, on the whole, scanty, and consists of the same species 

 as are to be found on clayey soil, together with some Hupnacece, 

 Philonotis, etc. on damper soil. 



Near the Sulphur Springs proper the Bryophyte vegetation 

 is extremely scanty, and the ground is often quite bare of vegeta- 

 tion as far as the hot vapours extend. Sphagnum and Hupnacece 

 are entirely absent, whereas the majority of the Hepaticce are to 

 be found, especially Haplozia crenulata, Fossombronia Dumortieri, 

 Gymnocolea inflata, Alicalaria scalaris, Preissia commutata together 

 with Archidium phascoides, Polytrichwn commune and a few other 

 mosses. Riccia spp. (bifurca, sorocarpa and crystallina) belong spe- 

 cially to the dry, warm ground in the neighbourhood of sulphur 

 springs. 



The following species have been found on warm ground: 



1. Species which occur only on warm ground. 

 Riccia crystallina L. Thorlakshver. 



Riccia sorocarpa Bisch. Laugarashverir. 



bifurca (Hoffm.) Lindenb. Myvatn; Reykjanes; Kverkfjall. 



Anthoceros punctatus L. Common. 



Fossombronia Dumortieri (Hiiben.) Lindb. Everywhere. 



Calypogeia Trichomanis (L). S. F. Gray. Myvatn; Reykholtdalur; 

 Englandshverir; Sydri Reykjahver; Geysir. 



Odontoschisma Sphagni (Dicks.) Dum. Reykholtdalur. 



Sphagnum imbricatum Hornsch. Thorlakshver; Laugarahverir. 



Sphagnum cymbi folium (Ehrh.) Hedw. Common. 



Sphagnum Dusenii C. Jens. v. falcatum Reykholtdalur. 



Archidium phascoides Brid. Very common everywhere. 



Enlosthodon ericetorum (Bals. et de Not.) C. M. Reykholtdalur; 

 Englandshverir. 



Campylopus flexuosus (L.) Brid. Reykholtdalur. 



Campylopus fragilis (Dicks.) Br. eur. Laugarashverir. 



Barbula fallax Hedw. var Icevifolia n. var. Thorlakshver. 



Catharinea undulata (L.) Ehrh. f. thermophila Thorlakshver; 

 Laugarashverir. 



2. Species which are mainly distributed over warm 



