510 A. HESSELBO 



rarer. It is most frequent in rather damp situations, for instance on 

 rocks near waterfalls. Only sterile specimens have been found. 



220. Leskea nervosa (Schwiigr.) Myrin. 



SE. Iceland: Hofl, on roelus in company with Metzgeria fiircata, 

 sterile. S. Iceland: Drångshlid!; Hrutafell!, sterile. In both the latter 

 localities it occurred abundantly on dry tuflf-faces or on large fallen 

 blocks. 



221. Leskea catenulata (Brid.) Mitten. 



Nupsdal (Stp.)!. 



Here, Gnupsdalur near Dyrafjordur in NW. Iceland is probably meant. 



222. Anomodon viticulosus (L.) Hook. et Tavl. 



S. Iceland: Hrutafell!; cave near Skogafoss!. VestmannaejM. 



On Vestmannaey it grew at the foot of a dry, stony slope below 

 Stora Klit; near Hrutafell it grew sometimes on rocks, sometimes on 

 soil-covered rock-ledges. Only sterile specimens have been found. 



223, Pterigynandrum filiforme (Timm) Hedw. 



Very common everywhere. 



The most frequent form is var. decipiens (W. et M.) Limpr., which 

 occurs abundantly everywhere on drj' rocks, especially on perpendicular 

 basalt-faces, where it often forms very large cushions 5—6 cm. deep. 

 Here all transitional forms are also met with between the type and the 

 variety. The type is developed in deeper shade and occurs especially 

 in clefts and crevices, where it forms thin. adherent mats on the sur- 

 faces of stones. Only sterile specimens have been found. 



Both forms are common up to about 300—400 metres above sea-level. 



224. Lescuræa decipiens (Limpr.) 

 Ptychodhiin decipiens Limpr. 



E. Iceland: Berufjordur !^, at an altitude of 80 metres. 



var. crassirefe n, var. 



Leaf-cells very thick-walled, highly porous and distinctly papillose 

 in the upper half of the leaf. Nerve very strong, 0.040-0.045 mm. 

 broad for almost its entire length. 



NW. Iceland; Gnupsdalur, at an altitude of 280 metres!. 



L. decipiens is closely alUed to L. saxicola and is often difficult to 

 distinguish from the latter species. Peculiar to both are the narrow, 

 highly thickened and porous leaf-cells, which in L. decipiens are more 

 or less distinctly papillose with a papilla at each of the uppermost 

 cell-angles, at the back towards the leaf-apex; while L. saxicola almost 

 always has quite smooth leaves. In L. saxicola the upper half of the 



