426 A. HESSELBO 



Grl.")!; Esja!, coninion up to about 400 metres above sea-level; Hafnar- 

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

 Seljaland!; Austerhlid near Gej^sir!. 



This species has ils 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 Ihe margin 

 of streams. Thus, near Sej'disfjordur it occurred abundantly along several 

 rivers. In such localilies 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 Gjå it usually grew at the bottom of the com- 

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

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

 paratively drj' localities have alwaj'S deeply-toothed leaves while the 

 aquatic forms have less deeplj'-toothed, sometimes almost entire leaves^ 

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

 are however ahvays more highly thickened than in the latter s|)ccies, 

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

 and narrower obovate (in S. undnlata almost circular). (^ piants and 

 fruit are of frequent occurrence. 



84. Scapania undulata (L.) Dum. 



Very common on stones and gravellj' soil in rivers, occasionallj^ 

 also on inundated ground in swamps and moss bogs. 



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

 300 metres, and forms there, cspecialh' creeping over stones in the 

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

 scyphns polyanthns var. frayilis and Haplozia cordifoUa. Not rarely it is 

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

 grew abundantly on slopes irrigated jjy melting snow, 400 — 500 metres 

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

 abundanth' in a stream even at an altitude of about 600 metres. Tlic 

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

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

 It is frequently found in fruit. 



The leaves are entire or have a few obtusc tccth 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. dcntata and from the large 

 aquatic forms of 5. irrigua. The latter, however. have always cells more 

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

 walled leaf-cells. 



85. Scapania curta (Mart.) Dum. 



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

 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 



