472 A. HESSELBO 



with everywhere on damp ground. oflcn forming the bulk of the 

 vegetation, for instance in sevcral piaces in NW. Iceland. It is, howevcr. 

 aJso comnion in the more low-lying districls, where it grows especiall}' 

 on damp soil along streams. 



Pohlia vommntata is a most variable species, and occurs in Iceland 

 in nnmeroiis forms. The tufts are, as a rule, loose, and as niuch as 

 (3 cm. high. In more particularly sheltcred localities, for instance in 

 lava-clefts near Thingvellir, the piants are very vigorous, and form deep, 

 not-coherent tufts which are hardly tomentose. But in damp depressions 

 on the mountain heights they often form extensive, deep and dense 

 cushions which are brownish grey in the interior and yellowish green 

 only at the top; compact forms like this occurred abundantly on damp 

 gravelly flåts, 400—500 metres above Isatjordur. The single piants are 

 slender, with a thin fragile stem, and with leaves appressed, shorth' 

 jiointed, slightly toothed towards the apex and longly decurrent. The 

 leaf-cells are shorter, sometimes thin-walled, sometimes rather highly 

 thickened and porous, but both the form of the leaves and of the cells, 

 and the thickness of the walls may vary considerably in the same tuft 

 or even on the same plant. 



The fruit, which occurs rathcr frequently, was usually ripe at the 

 end of July. 



127. Pohlia gracilis (Schleich.) Lindb. 



Very common. 



In the lowlands this species grows, as a rule, on damp ground 

 along streams, either in unmixed tufts or, more often, associated with 

 Aliciilaria scalaris, Lophozia quinquedentata, Cephalozia biciispidata, Pohlia 

 commutata, etc. On cold, wet gravelly ground it is sometimes the most 

 abundant constituent of the vegetation; thus it was growing in enormous 

 ([uantity bclow the "'Jokull" in Kaldalon (XW. Iceland). In the Alpine 

 legion from about 300—700 metres, Pohlia gracilis is one of the most 

 frequentlj" occurring species, and grows everj^where on damp gravelh^ 

 flåts, chiefly scattered among other mosses such as Anlhelia Juratzkana. 

 Aliciilaria spp. , Polytrichiim sexanyiilare and Oligotrichiim hercynicum, 

 more rarely in larger, unmixed growths. 



The fruit, which occurs very frequently, ripcns on the mountain 

 heights usually at the end of July, in the lowlands a month earlier 

 (Kaldalon, June 22). 



128. Pohlia Rothii (Correns) Broth. 

 Pohlia annotina (^L.) Lindb. 



■ 



N. Iceland: Husavik c?!; Stadr near Hrutafjordur !. 



It was growing in both piaces on damp sandy soil, associated with 

 Dicranclla crispa , Aonyslræmia longipes and Hepalicæ. The gemmæ, 

 which occurred only few in number, were quite typical. 



Wehera annolina Hedw. is recorded from the peninsulas of NW. 

 Iceland (Stp.) and from Hafnarfjordur (Grl.\ but as the collections con- 



