THE BRYOPHYTA OF ICELAND 569 



moreover, Haplozia sphcerocarpa woven into the Catharinea-cushions. 

 All the mosses had developed to an unusual height and vigour, 

 especially Catharinea which occurred in a peculiar form (f. thermo- 

 phila) and formed large cushions more than 10 cm. deep. The same 

 vigorous moss vegetation, associated with grasses and sedges, was 

 also found on the flat above the steep bank, as far as the influence 

 of the warm vapours was felt. 



Where the banks were low, so that the hot water partially 

 flowed over and mixed with the cold water of the boggy ground, 

 the usual bog or stream -bank vegetation was developed, which 

 nearest to the outlet, in hot water of a temperature of about 25 

 30, consisted of a very slender form of Philonotis fontana, associa- 

 ted with some Hypnum stramineum and Catoscopium nigritum. 



The Hypnum-be\\. mentioned above gradually merged into the 

 usual grassland vegetation; most of the species of which (for in- 

 stance Rhacomitrium canescens, R.hypnoides, Philonotis, Mniobryum 

 albicans and Hypnum uncinatnm) were also found intermixed with 

 the thermophilous vegetation proper. 



A short distance from the main group of the hot springs, on a 

 small, flat piece of ground near the river, there are some small 

 holes, some of which emit boiling water, and some vapours im- 

 pregnated with sulphuretted hydrogen. The ground around these 

 holes consists of a rather dry, warm (30 -40), clayey soil, with a 

 very sparse vegetation. Archidium is common everywhere; Fossom- 

 bronia often grows around the holes, and here and there on the 

 clayey flats Riccia crystaUina and Anthoceros punctatns. 



Laugarashverir (Fig. 22) are situated in the southernmost part 

 of Biskupstungur, near the farm Laugaras. At the foot of the slope 

 on which the farm is situated, and in the boggy ground below, 

 there issue several boiling hot springs which, through several 

 channels, unite and form a large brook which flows into the Tun- 

 gufljot. The vegetation is very much like that in Thorlakshver. 

 Next to the water there is a belt of Fossombronia , Haplozia crenu- 

 lata, Alicularia and Archidium with a ground temperature of as much 

 as 43; then comes the Sphagnum-belt which is composed of S. sub- 

 nitens var. coerulescens , S.teres, S. an gusti folium, S. cymbifolium , S. 

 imbricatum and S. inundatiim in association with Hypnum strami- 

 neum. The warm ground between the channels was covered with 

 extensive mats of Hypnum imponens, H. Lindbergh, H. stramineum, 

 Hylocomium squarrosum , Climacinm dendroides, Thiiidium delicatu- 



The Botany of Iceland. Vol. I, part II. 37 



