THE BRYOPHYTA OF ICELAND 575 



gathers into a broad brook which flows into the river. The whole 

 hill, which consists of reddish clay, is warm throughout, and at 

 the top the temperature was 06 3 40 just below the surface of the 

 ground. 



On the slope stretching down towards the springs Hlasia pu- 

 silla grew abundantly, occasionally in companj r with Fossombronia 

 Dumortieri. The dry ground on the top of the hill was covered 

 with large patches of Campijlopus flexuosiis and Hypinim imponens 

 intermixed with scattered tufts of Catharinea undalata and Oligo- 

 trichum hercynicum and entirely interwoven with Gymnocolea in- 

 flata. At the foot of the hill, but on the opposite side to that on 

 which the springs lie and where the ground was damper, grew, in 

 addition to the above-mentioned species, Sphagnum cymbi folium 

 and Polytrichum gracile. Here some 5 6 small plants of the fern 

 Blechnum spicant were also found. 



The warm brook below the hill divides into several branches, 

 which flow round some large islands saturating them with the 

 warm water. Here Sphagnum papillosum, S. angustifolium and Po- 

 lytrichum commune grew in enormous cushions, which were every- 

 where covered by the orbicular leaves of Hydrocotyle vulgaris and 

 entirely enshrouded in hot vapours. 



Geysir. On a low mound about one kilometre long and 

 about Vs a kilometre broad, situated about 100 metres above sea- 

 level, there are a great number of hot springs (about 40) besides 

 the well-known Great Geysir. The majority of these springs con- 

 sist of a larger or smaller hole, but sometimes of a basin, several 

 metres in diameter, in which the boiling water usually reaches to 

 the upper edge and flows over the somewhat raised rim, or is 

 ejected at shorter or longer intervals. The soil consists of reddish 

 clay, or nearest to the springs especially to Geysir of sili- 

 ceous sinter. The water in the majority of the springs smells 

 slightly of sulphuretted hydrogen. The whole district around the 

 springs is warm, and in many places the temperature is so high 

 that the tenants of the neighbouring farm (Laug) bake their bread 

 by putting the dough into a pot and burying it about 30 40 cm. 

 below the surface of the ground. 



The siliceous sinters are quite bare of vegetation. The warm 

 clay-flats situated on a higher level are, as a rule, dry, and either 

 bear a greatly scattered Bryophyte vegetation or are quite bare. Un- 

 der the scattered, low cushions of Ditrichum homomallum, Archi- 



