THE BRYOPHYTA OF ICELAND 499 



the stems. This form grew abundantly near the hot springs about 

 Skalholt, especially on the slopes stretching down towards the outlets 

 of the springs. 



195. Oligotrichum hercynicum (Ehih.) Lam. 



Oligotrichnm incurviim (Huds.) Lindb. 



Iceland (Morch). E. Iceland: Seydisfjardarheidi!. N. Iceland: Ljosa- 

 vatn!, common 350 metres above sea-level and upwards; Askja (Caroc)!. 

 NW. Iceland: Very common!. \V. Iceland: Stadarfell ;Stp.); Esja!, at an 

 altitude of 400 500 metres; Reykholtdalur (Grl.;!); Hafnarfjordur!. S. 

 Iceland: Common from about 350 metres and upwards!; Krisuvik (Stp.)!; 

 everywhere near hot springs!. 



This species has a very peculiar distribution in Iceland. It has 

 its main area of distribution on the mountain heights, where it doubt- 

 less occurs over the whole of Iceland, and often in masses. It grows 

 here on damp gravelly flats, especially in the neighbourhood of the 

 snow-patches, in association with Anthelia Jarat-kana, Pleiiroclada albes- 

 cens, Pohlia gracilis, Polytrichum sexangalare, etc., and as a rule sets 

 fruit. Scarcely anywhere has it been found until at a height of 350- 

 400 metres, and was most abundant at about 500 700 metres above 

 sea-level. Only in NW. Iceland, where it is exceedingly common, did it 

 descend to a lower altitude, in man} 7 places as low as to the sea-level. 

 In the greater part of the country it is quite absent from the low land; 

 in SW. Iceland it has been found only scantily in a lava cave near 

 Hafnarfjordur. 



This species has another area of distribution near the hot springs 

 in SW. and W. Iceland. Here it has been collected near a great number 

 of springs in Reykholt- and Reykirdalur, around Skalholt and in several 

 other places, where it often occurs abundantly on the warm clayey flats, 

 but only sterile. These warm-soil forms differ somewhat from the Alpine 

 forms. As a rule they are quite low in growth, about 510 mm. high, 

 with softer leaves, twisted or incurved when dry, with a few (56) 

 lamellae at the back. The leaf-cells are more thin-walled, chlorophyllous, 

 larger and more regularly quadrate and transversely elongated, usually 

 0.0150.018 mm., but occasionally also 0.025 mm. in diameter, shortly 

 rectangular at the base, 0.018 mm. broad. The nerve is often only half 

 as broad as in the Alpine form. Such forms grow especially on the 

 warm clayey flats, in company with Anthoceros, Fossombronia, Haplozia 

 crenulata and other hepatics. Near Deildartunguhver in Reykholtdalur 

 it grew on the warm ground among other mosses, in tufts about 3 cm. 

 high. Forms exactly resembling the Alpine forms occur also frequently 

 on the warm ground. 



In the majority of the localities in NW. Iceland the fruit was ripe 

 in the latter half of June, on the mountain heights early in July. 



