THE BRYOPHYTA OF ICELAND 563 



of the surface decreases, the most hygrophilous species disappear 

 and some other species, chiefly mesophilous, take their place.. Some 

 of the latter are especially connected with this soil. The most 

 marked species of peaty soil are Psilopilum Icevigatam, Polytrichum 

 gracile, P. jimiperinum , Pogonatum polytrichoides, Mnium hornum, 

 Catharinea undulata (also in warm soil) and Dicranella ceruiculata. 

 Some species which occur on other soils, but most abundantly on 

 peat, are Philonotis tomentella , Pogonatum urnigerum, Funaria hy- 

 grometrica, many Bryum spp. (especially B. inclinatum, B. affine, 

 B. arcticum, B.lacustre and B.pallens), Pohlia nntans, Leptobryum 

 pyriforme, Distichium inclinatum, Ceratodon pnrpureus and Dicranella 

 crispa. The above-mentioned species are all mesophilous, a few 

 are xerophilous also (for instance P. jumper in am and Ceratodon), 

 and the majority of them occur also in sandy soil, but in Iceland 

 the peat is often abundantly mixed with fine sand , transported by 

 the wind. The two rare species, Trematodon ambiguus and Pogo- 

 natum capitlare var. dentatum, have also been found on peat. 



The most decided character-plant of peaty soil is Psilopilum 

 Icevigatam, which occurs everywhere on peat-fla\s which have been 

 laid bare, and may, for instance, entirely cover the piled-up heaps 

 of cut peat with its numerous capsules, often in association with 

 Funaria hygrometrica. Another characteristic vegetation of localities 

 like these consists of extensive bluish-green mats of low-growing, 

 sterile Pogonatum urnigerum, interwoven with Alicularia scalaris. 



The following examples will show the composition of the peat 

 bogs in the different parts of Iceland: 



1. Seydisfjordur. In a peat bog intersected by ditches: 

 Psilopilum Icevigatum, Leptobryum pyriforme, Pogonatum urnigerum, 

 Polytrichum jimiperinum and P. alpinum grew abundantly. Inter- 

 mixed with the above occurred Bryum inclinatum, B. arcticum, B. 

 purpurascens, Distichium montanum, Ceratodon purpureus, Scapania 

 curta, Alicularia scalaris and Lophozia Wenzelii. 



2. Akureyri. Behind the town, at the foot of the mountain, 

 were large expanses of bogs from which great quantities of peat 

 had been removed. The bared flats and the piled-up heaps of cut 

 peat were often entirely covered with Psilopilum and Funaria. 

 Commonly occurring species were Polytrichum gracile, P. alpinum, 

 P. juniperinum , Leptobryum pyriforme, Bryum inclinatum, B. affine 

 B. lacustre, B. arcticum, Philonotis tomentella, Ceratodon purpureus. 

 Dicranella crispa, Didymodon rubellus and Scapania irrigua. 



