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 lævigatum, Polytrichum 

 gracile, P.juniperiniiin, Pogonatum polytrichokles, Mnium hornum, 

 Catharinea iindiilata (also in warm soil) and Dicranella cerviciilata. 

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

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

 grometrica, many Bryuni spp. (especially B. inclinatiim , B. affine, 

 B. arcticiim, B.laciistre and B. pallens) , Pohlia nntans, Leptobryum 

 pyriforme, Distichium inclinatum, Ceratodon purpureus and Dicranella 

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

 are xerophilous also (for instance P.juniperinuni 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 capillare var. dentatum, have also been found on peat. 



The most decided character-plant of peaty soil is Psilopilum 

 lævigatum, which occurs everywhere on peat-flats 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 lævigatum, Leptobryum pyriforme, Pogonatum urnigerum, 

 Polytrichum juniperinum 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 flåts 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. affme 

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

 Dicranella crispa, Didymodon rubellus and Scapania irrigua. 



