426 A. HESSELBO 



(Grl.)!; Esja!. common up to about 400 metres above sea-level; Hafnar- 

 fjordur!. S. Iceland: Krisuvik (Stp.)!; Krokr (H. J.)!; Almannagja!; Holt!; 

 Seljaland!; Austerhlid near Geysir!. 



This species has its main distribution in E. and SW. Iceland and 

 it has not been found in NW. Iceland. It grows especially on wet rocks 

 and often in the water itself, but also on gravelly soil along the margin 

 of streams. Thus, near Seydisfjordur it occurred abundantly along several 

 rivers. In such localities it forms extensive reddish brown cushions 

 several centimetres deep. 



On damp soil and on rocks it forms low cushions, green, rose-red 

 or reddish-brown in colour. In the lava-fields near Hafnarfjordur and 

 Thingvellir and in Stora Gja it usually grew at the bottom of the com- 

 paratively dry caves and clefts in small, flat tufts of a peculiar 

 yellowish-green or beautiful rose-red colour. Such forms from com- 

 paratively dry localities have always deeply-toothed leaves while the 

 aquatic forms have less deeply-toothed, sometimes almost entire leaves, 

 in which feature they approach S. undiilata very closely. The cell-walls 

 are however always more highly thickened than in the latter species, 

 especially .at the angles, and the postical lobe of the leaves are longer 

 and narrower obovate (in S. midnlata almost circular). $ plants and 

 fruit are of frequent occurrence. 



84. Scapania undulata (L.) Dum. 



Very common on stones and gravelly soil in rivers, occasionally 

 also on inundated ground in swamps and moss bogs. 



This plant occurs most frequentty in the low land up to about 

 300 metres, and forms there, especially creeping over stones in the 

 shallow water along rivers, extensive growths in association with Chilo- 

 scyphns polyanthus var. fragilis and Haplozia cordifolia. Not rarely it is 

 also met with at higher levels, for instance near Dyrafjordur, where it 

 grew abundantly on slopes irrigated by melting snow, 400 500 metres 

 above sea-level; and near Holt below Eyjafjall, where it was found 

 abundantly in a stream even at an altitude of about 600 metres. The 

 aquatic forms are usually green; in swamps and moss bogs it often 

 forms extensive, thick carpets, reddish-brown or almost purple in colour. 

 It is frequently found in fruit. 



The leaves are entire or have a few obtuse teeth at the margin, 

 but forms sometimes occur with more deeply toothed leaves or even 

 with the leaf-margin entirely toothed, in the latter case it may be 

 difficult to distinguish the plant from S. di'ntata and from the large 

 aquatic forms of S. irrigua. The latter, however, have always cells more 

 thick-walled especially at the angles, while S. undulata has always thin- 

 walled leaf-cells. 



85. Scapania curia (Mart.) Dum. 



Common on rocks coated with soil, damp sandy or gravelly Around 

 and on peat, occasionally also on boggy ground up to about 400 metres 

 above sea-level. Near Isafjordur and in Esja it was collected at an 



