THE BUYOPHYTA OF ICELAND 547 



Orthotrichum lilijttii occuis liere and there on coast rocks, or at 

 anv rate in the imniediale nei^hbourhood of the coast. Pottui Heimii 

 is coninionly distributed along all flat coasts and Amblystegiiun 

 liilorale occurs here and there on damp sandy soil. 



Besides these liltoral species proper, there are severai others 

 which occur especially abundanlly on Ihe coast, but are also distri- 

 buted in niany other localities. Brijuin (ircjenteum and B. aipiUare 

 grow especially below clitTs inhabiled by sea-fowl. but their pre- 

 sence there is, no doubt, as niuch due to the abundant supply of 

 organic manure at lo the proximity of the sea. Desmatodon lati- 

 foliiis, Leptobrijiim pyriforme and Tortilla niralis are also typical of 

 damp sandy soil and Hijpniim polygamiim of saline, boggy soil. 

 On damp sandy soil on Ihe beach low, scattered moss-cushions 

 consisting of stunted individuals of many different and more casual 

 species are often met with, for instance, Distichiiim montaniim, Di- 

 dymodon riibellus, Ceratodon piirpiireiis , Encalypla rhabdocarpa, 

 Myurella jiilacea, Bryiim spp., etc. 



Hydrophilous Bryophyte Formations. 



The water originating from rain and mist or from melting 

 snow will, according to the local conditions and the inclination, 

 eilher spread out over the ground and — if it consists of humus 

 or sand — sink into it, or seek outlets in brooks and rivers. Where 

 the water remains standing without being able to find a sufficient 

 outlet, a bog vegetation is developed, or, in deeper hollows, a lake 

 is formed. Part of the water which sinks down to the solid rocky 

 substratum continues ils way downwards along the latter until it 

 sooner or later issues as a spring. Stagnant water conlains humus 

 substances, is not well aeraled, and is warmed by the sun, while 

 running water, both in streams and springs, is pure and clear and 

 conlains oxygen and carbonic acid. Running water has a very low 

 temperature during the summer, at the most 4° — 6°. Therefore 

 the composition of the vegetation on boggy ground ditTers entirely 

 from Ihat on ground along streams and near springs, inundated or 

 saturated bj' the pure water. 



The hydrophilous formations may be classified as follows: — 



