444 A. HESSELBO 



it often occurs abundantly. It grows on wet boggy ground in loose 

 tufts as much as 6 cm. high, either pure or mixed with Sphagna and 

 Hypniim stramincum and interwoven with Hepaticse such as Lophozia 

 quinquedentata, Scapania irrigua, Cephalozia pleniceps, etc. Only sterile 

 specimens have been found. 



This species is most widely distributed in the lowlands and has 

 only once been collected at an altitude of 400 metres on Asolfskalaheidi, 

 where it grew plentifully in a bog. 



Hag en (Musci Norv. Borealis, p. 22) states that D. angustum differs 

 from all nearly allied species, and especially from D. scoparium, in having 

 thin-walled cortical cells; but this distinction does not suffice as regards 

 bog-forms of D. scoparium as in the latter species all transitional stages 

 are found from the thin-walled, hyaline cortical cells of plants from 

 wet ground to the thick-walled, brown cells of xerophilous forms. 



29. Dicranum majus Smith. 



NW. Iceland: Dyrafjordur!; Sugandafjordur!; Isafjordur!. W. Iceland: 

 Neshraun (H. J.)!; Budahraun (H. J.)!. 



In the two habitats in W. Iceland, both of them on Snsefellsnes, 

 the plants were collected in depressions in the lava-field. In NW. Ice- 

 land, where it is commonly distributed, it grows on the ground on 

 slopes covered with birch coppice, Vaccinium, etc., as far upwards 

 as about 300 metres above sea-level. 



The majority of the plants collected have slightly secund leaves 

 and entirely resemble D. scoparium in habit. A vigorous form with 

 strongly falcate leaves was found in a birch coppice near Dyrafjordur 

 at an altitude of about 150 metres. Only sterile specimens have been 

 found. 



30. Dicranum scoparium (L.) Hechv. 



Very common. 



D. scoparium is most widely distributed in the more low-lying parts 

 of the country up to a height of about 400500 metres, but also ascends 

 frequently to about 700 metres above sea-level. In S. Iceland it appears 

 to be more rare and, as for instance on Fljotshlid and south of Eyja- 

 fjall, was only found in a few localities and very scantily. It grows 

 both on rather dry and on damp ground, and also on rocks and on 

 knolls in bogs, and varies considerably. Orthophyllous forms are the 

 most common, especially on damp ground, while more or less distinctly 

 drepanophyllous forms grow by preference in dry localities, for instance 

 in lava-fields and on rocks. In bog-forms the leaves are slightly undulate 

 at the apex, in which feature it approaches D. Bonjeani. The leaf-apex, 

 especially in orthophyllous forms, is usually short and broad, and 

 faintly toothed, or even quite entire, at the margin, at the same time 

 the lamellse on the back of the leaves develop more slightly or dis- 

 appear almost entirely. Such forms agree well with var. in leg ri folium 

 Lindb. 



Fruit is found rather rarely; in Nordredalur it was fully developed 

 on August 2nd, but was still green. 



