566 A. HESSELBO 



boiling point, they are called in Icelandic "hver" (plur. "hverar"), 

 if the temperature is lower, they are called "laug" (plur. "laugar"). 



The Sulphur Springs (Icelandic "brennistenshverar") are most 

 numerous in districts where the effect of the volcanic activity is 

 still felt, for instance near Myvatn and in many parts of South 

 Iceland. The water contains sulphuretted hydrogen. These springs 

 deposit sulphur, and the soil around them is greatly decomposed 

 by the acid vapours which arise, and is transformed to red or 

 yellowish clay-masses. Sometimes, as for instance in Reykirdalur, 

 they also deposit siliceous sinter. As a rule, a group of springs 

 consists of either the one or the other kind of spring, occasionally, 

 however, a few springs containing sulphuretted hydrogen may be 

 found together with the alkaline springs. The vegetation around 

 sulphur springs is ahvays very scanty, since only a few species of 

 piants can thrive were they are exposed to hot vapours containing 

 sulphuretted hydrogen. 



The "Laugar" near Reykjavik. The vegetation has been described 

 by Ostenfeld (Bot. Tid. , vol. 22, pp. 233 et seq.), who has not, 

 however, mentioned the moss vegetation. When I visited the 

 springs in 1909 and 1912 I found no characteristic moss vege- 

 tation. Since the warm water had been used for washing purposes 

 the ground surrounding the spring had been much trampled upon, 

 and further downwards tow^ards the warm outlet only the usual 

 bog species were found. Here Philonotis fontana alone formed the 

 elongated slender form known also from other hot springs. 



The Springs on Biskupstungur. On the low boggy tract of 

 land between the rivers Bruarå and Tungufljot in South Iceland 

 (Biskupstungur, so called because the old episcopal residence — 

 Skålholt — was situated there), there are, on both sides^ along the 

 rivers several hot springs of considerable size, or groups of hot 

 springs of which Thorlåkshver and Laugaråshver in the southern- 

 most part, near Skålholt, and Svdri Reykjahver, further northwards 

 near the Bruarå, have been investigated. They all contain pure 

 water free from sulphuretted hydrogen, with the exception of a few 

 small holes near Thorlåkshver. 



Thorlåkshver (Fig. 21) is situated a few kilometres west 

 of Skålholt, close to the east bank of the Bruarå. It consists of 

 one larger and several smaller holes, from whence the boiling 

 water flows out and gathers together inlo a rather large brook, 

 w^hich tlows into the Bruarå. The vegetation along the sloping 



