494 A. HESSELBO 



Fam. BARTRAM i ACEÆ. 



186. Bartramia ityphylla (Haller) Brid. 



Very common. 



One of the most frequent niosses, both on a dry and on a some- 

 what damp substratum, from the lowlands to far up in the Alpine 

 region. It grows in soil-filled rock-clefts, on dikes and house-walls, on 

 peat and on the top of knolis in bogs. As a rule, it grows in small, 

 unmixed tufts, but occasionally also mixed with other mosses. The 

 fruit, which ripens during Augu.st, occurs plentifully everywhere. 



187. Plagiopus CEderi (Gunn.) Limpr. 

 Bartramia CEderi (Gunn.) Sw. 



E. Iceland: Berufjordur!, fr. N. Iceland: Hof near Eyjatjordur O. 

 D.)!; Reistarargil (O. D.)!, fr. 



Near Berufjordur it grew abundantly on a wei rock-face with a 

 northern exposure, in cushions, about 3 cm. high, with numerous cap- 

 sules which were ripe at the end of June. 



188. Philonotis fontana (L.) Brid. 



Very common over the whole of Iceland. 



One of the most frequent and abundantly occurring species which 

 grows everywhere on a wet substratum, in marshes and moss bogs, 

 along streams, and on wet rocks, but is also common on a more dry 

 substratum, for instance in grass fieids or on humus-covered rocks. It 

 is of almost equal frequency at all elevations upwards to the limit of 

 vegetation. The fruit, which is found very frequently, ripens in the low 

 land about August Ist. 



Philonotis fontana is extremely variable, and conditions pertaining 

 to dampness especially exercise great influence over the appearance of 

 the plant. The usual bog forms are highly tomentose, with erect or 

 more or less falcato-secund leaves (f. falcata Warnst.). On a more dry 

 substratum the tufts usually become denser and more highly tomentose, 

 and the piants more slender. 



In the cold water in moss bogs and on inundated ground along 

 rivers where the temperature during summer is often only 4'^— 6^ this 

 species, in association with Pohlia albicans var. glacialis, Brachytheciiim 

 rivulare and species of Mniiim, often forms the main part of the vege- 

 tation. Here it forms very high and loose, in faet hardly cohering, 

 tufts, which often resemble P. seriata in habit. The stems are flaccid 

 and hardly tomentose; the leaves are short and appressed or slightly 

 secund, and often obtuse or cucullate at apex. The nerve is very broad 

 and widened at the base. Such cold-water forms agree exactly with 

 Loeske's P. fontana-adpressa (L. Loeske, Kritische Bemerkungen iiber 

 einige Formen von Philonotis, Hedwigia, vol. 45, p. 100, and Kritische 

 Ubersicht der eur. Philonoten, Hedwigia, vol. 45, p. 195). That it is the 

 cold water which checks the growth of the radicles and causes the 



