THE BRYOPHYTA OF ICELAND 581 



fontana, Anlacomnium palustre or of an abundance of species inter- 

 mixed. The commonest of these species are: Hypniun imponens 

 and //. Lindbergii, which are often the most abundant constituents 

 of the carpet, H. stramineum, Hylocomium squarrosiim, Acrocladium 

 cuspidatum, Thiiidium delicatulum, and numerous other bog-mosses 

 such as Hypnum reuoluens, H. molluscum, Catoscopium nigritum, 

 Fissidens osmundoides, Scapania irrigna, Pellia Neesiana, Anenra 

 pinguis, etc. Especially the first six species, however, occur every- 

 where in abundance, and often attain an unusual size and development. 



As an intermixture in this moss carpet some species, for in- 

 stance Mnium hornum, Catharinea undulata and Polytrichum gracile, 

 are occasionally met with which partly occur also in other localities 

 and are partly characteristic of warm ground, and in Iceland only 

 occur in such. To the latter group belong in addition to Hyp- 

 nnm imponens, which is rare elsewhere Enthostodon ericetorum, 

 Calypogeia Trichomanis, Aneura multifida (found scantily in one spot 

 on cold boggy ground) and Odontoschisma Sphagni. Some species 

 develop special warm-soil forms: Catharinea undulata f. thermophila 

 is exceedingly vigorous, as much as 10 cm. high, with long, ex- 

 tremely wavy, secund leaves right up from the base. Philonotis fon- 

 tana becomes thread-shaped in warm ground, with long, branchless, 

 barely tomentose shoots (Fig. 8), Hypnum Lindbergii develops a similar 

 form with almost branchless, erect stems with scattered leaves, and 

 Hypnum imponens is also, as a rule, much elongated and slightly 

 branched. Comp. further Bryum sp. (Fig. 24). On drier, clayey 

 ground the Hypnum carpet is replaced by other species. Archidium 

 phascoides is extremely common, and often forms extensive growths 

 both near alkaline springs and near springs containing sulphuretted 

 hydrogen. Here Campylopus flexuosus, C. fragilis, Oligotrichum hercy- 

 nicum, Catharinea undulata, Gymnocolea inflata and several other 

 species are also to be found. 



In damp clayey soil, especially along the outlets of the hot 

 springs, both where the water is pure and where it contains sul- 

 phuretted hydrogen in small quantities, without however depositing 

 sulphur, a low Bryophyte carpet occurs composed of specie smostly 

 Hepaticce the majority of which are only met with in warm soil. 

 Haplozia crenulata, Fossombronia Dumortieri and Oligotrichum hercy- 

 nicum are also common. Preissia commutata is common in Reyk- 

 holtdalur, Alicularia geoscypha and Aongstrcemia longipes and a few 

 other species occur here and there. 



