502 A. HESSELHO 



foiind at i\ liigher level than 200—300 metres. Near Akurej'ri the f'ruit 

 was ripe at tlie end of July. 



Var. amnualnm (Milde) Hagen. 



Hof near Eyjafjordur (O. D.)!. NW. Iceland: Hesteyri!. 



In both tliese piaces it was collected scantily only. Near Hof it 

 occiirred as a few scattered individuals in a specimen of the vegetation 

 taken from wet boggy ground. Near Hesteyri it grew on very wet boggy 

 ground. The piants were about 3 cm. high and sterile. Some of them 

 agreed Nvith var. anomahim ; in some the leaves at the base of the stem 

 rcsembled in structure those of the variety in having thin-walled cells 

 0.020—0.025 mm. in size, while the leaves in the upper part of the 

 stem resembled in structure those of the type in having cells 0.015— 

 0.020 mm. in size. 



Var. anomahim is undoubtedly a hygrophilous form of P. gracik. 

 which develops when the habitat is inundated. 



203. Polytrichum sexangulare Fioercke. 



Iceland (Morch)!. N. Iceland: Ljosavatn!; Reykjaheidi!; common near 

 Eyjafjordur (O. D.;!). NW. Iceland: Very common!. W. Iceland: Esja!; 

 Kolvidarhol!. S. Iceland: Seljaland!; Holt!; Thingvallahraun !. 



Var. ntlcanica C. Jens. 



"Sela perbrevis usque ad 4 mm. longa; apophysis valde indistincta; 

 ca|:)sula non angulata, vetusta nigrescens et irregulariter 4— 5-gona ; 

 Cetero typo simile." 



S. Iceland: The volcano on the road to Holt (Stp.)!. 



Var. teneUtim n. var. • 



Piants 1—2 cm. high, more slender than the type, with shorter, 

 narrower, more slighth' incurved and not secund leaves, when dry; the 

 nerve excurrent in a short mucro; otherwise exactlj' like the type. 



S. Iceland: Barkarstadr!; Drangshlidl; Seljaland!. 



Polytrichum sexangulare has a ver}'^ peculiar distribution in Iceland. 

 The type is a decidedly Alpine plant which does not feel quite at home 

 until near the snow line, on the gravelly flåts soaked by the melting 

 snow. In N. Iceland it has been collected only at elevations of above 

 500 metres. In NW. Iceland, where the species is very common, it is 

 met with everywhere from about 200—300 metres upwards. On northern 

 slopes where the snow lies long it sometimes descends as far down as 

 to the sea-level. Near Kolvidarhol it was common at about 400 metres, 

 and on Esja everywhere at elevations of above 500 metres. 



P. sexangulare has not j^et been collected in E. Iceland, but the 

 reason can hardly be that it does not occur there, it must rather be 

 due to the faet that the mountain heights were almost everywhere snow- 

 covered at the time of the year (June, 1909) when there was an op- 

 portunitj' of making collections there. This species has an area of dis- 

 tribution not only on the mountain heights, but also in the lowlands. 



