THE BRYOPHYTA OF ICKLAND 483 



The leaf-base, at any rate in the lower leaves, is decurrent, with 

 elongated, narrow alar cells. The close-set uppermost leavcs are usuall}' 

 not decurrent, and then have the base rounded, with quadrate, some- 

 what widened alar cells. 



The structure of the leaf-base evidently depcnds on the degree of 

 dampness of the habitat. Bryiim caspidatiim usually grows on boggy 

 ground and forms liere tufts, 1—3 cm. high, with rather long innovations. 

 On such elongated shoots the leaves are always decurrent. On a more 

 dry and exposed substratum, for instancc on rocks, the tufts become 

 lower in growth and denser, and then the leaves are only slightly, or 

 not at all, decurrent, and in connection with this the alar cells are 

 Short as in Brijum cirrdtiim. 



148. Bryum cirratum Hoppe et Hornsch. 



Rather common. 



Grows in drier localities than does B. affine, for instance in gravelly 

 soil, on slopes and among grass. It is especialh' common in NW. Iceland, 

 and occurred abundantlj^ for instance on stony slopes near D\rafj6rdur. 



The forms which are here referred to B. cirratum have 9, $ and 



nunierous (^ flowers. The leaves are not decurrent, taper to a very long 

 point, with narrow, almost linear cells in the upper portion. The spores 

 are 0.014—0.020 mm., yellow, and finely papillose. Brijam affine and 7i. 

 cirratum form a continuous series of forms, in which B. affine represents 

 the hygrophilous and B. cirratum the xerophilous adaptation-form. 



149. Bryum intermedium (Ludw.) Brid. 



N. Iceland: Grimsej' (O. D.^!; VidimVri!; Stadr near Hrutafjordur !. 

 S. Iceland: Merkjåfoss (F.)!. 



Rather rare and scanty on damp soil. Near Stadr the fruit was 

 ripe on August Ist, but the lid still jjersisted. 



150. Bryum pallescens Schleich. 



Widely distributed. 



One of the most frequent species everywhere up to a height of 

 about 300 metres above sea-level. It usually grows on damp rocks, 

 where it often forms very large and deep cushions, with numerous 

 capsules; but it also occurs on damp soil. In South Iceland it is very 

 common everywhere on faces of tuff rocks. The plant is, as a rule, 

 monoicous, but very often hermaphrodile flowers are also met with, 

 containing many antheridia and a few archcgonia. 



151. Bryum subrotundum Brid. 



S. Iceland: Uxavatn F.)l. 



