THE BRYOPHYTA OF ICELAND f)39 



This specimen is not to be found in the collections ; on the other hand, 

 a specimen from Iceland, determined by Morch as Hypnum arcticum, 

 belongs to H. alpinum. 



Rather common in N. and NW. Iceland, where it grows on stones 

 in rivers, like the other species of Hygrohypnum. It does not ascend 

 higher than about 200 metres above sea-level (Isafjordur), and often 

 sets fruit which ripens in N. Iceland in the latter half of July. 



Hypnum alpinum varies considerably in leaf-form, leaf-tissue and 

 habit. ' 



The leaves, which are most often spreading, are occasionally fal- 

 cato-secund along the entire length of the stem, in which feature it 

 approaches H. dilatation in habit. The Iceland specimens of H. alpinum 

 approach, on the whole, H. dilatutum, both in habit, leaf form and struc- 

 ture of cell-tissue. The cells of the base of the leaves are often thickened 

 and slightly porous, and the alar cells are sometimes colourless and 

 thin-walled, sometimes yellowish with slightly thickened walls. The 

 leaf-form varies from almost orbicular to elliptic. The leaf-margin is 

 almost always finely toothed all round. 



I have, however, thought it more correct to refer all the Iceland 

 plants to //. alpinum, as at any rate the capsule and the perichgetium 

 corresponded exactly to those in this species. Thus, fully developed 

 cilia have never been found in the peristome. The leaf-cells are also 

 shorter than in H. dilatatum and in size agree most nearly with those 

 in H. alpinum. 



310. Hypnum ochraceum Turn. 

 Amblystegium ochraceum Lindb. 



Very common on stones in rivers up to 300400 metres above 

 sea-level, but only sterile specimens have been found. 



Varies considerably in size, habit, etc. 



Var. uni'ittafttni Milde often occurs in company with the type. 



Var. filifonne Limpr. is rather common in swiftly flowing rivers. 

 where it often covers the bottom for long distances. 



Note. Amblystegium polare Lindb. is recorded by Gronlund Tillaeg 

 til Islands Kryptogamtlora, Bot. Tids., 20, p. 113 to have been collected 

 near Vallanes by H. Jonsson. The specimen in question is in the 

 Botanical Museum in Copenhagen and is labelled "Dichodontium pellu 

 cidum, Polytrichum alpinum, Amblystegium polare, det. C. Jensen", but in 

 spite of a careful search it was not possible to find A. polare among 

 the specimens, so for the present the occurrence of this species in Ice- 

 land must be regarded as uncertain. 



311. Hypnum cordifolium Hedw. 

 Amblystegium cordifolium De Not. 



N. Iceland: Myvatn (Grl.)!. NW. Iceland: Grunnavikl, fr. 

 This species is also recorded from the Olfusa, Nesland, Litlu.Bor- 

 garkatlar and Thorodstadaengjar, but the plants from all these localities 



35* 



