997 



bogs are absent or rare in the bogs in the moiintains (e. g. Caltha, 

 Narthechim, Heleocharis, etc.) The real character-species of the 

 swamps and bogs persist however in the alpine region, namely 

 Eriophonim, Scirpus caespitosiis, Junciis sqiiarrosiis and Nardus. 



c. The Grimmia-heath formation. 

 The typical Grimmia-heath consists of a soft greyish-green 

 (when wet a somewhat yellowish-green) carpet of Grimmia hyp- 



pig. 191. Gi 



lia-heath on the top of Skjællingfjæld, Stromo (768 

 (From photo. by F. Borgesen). 



noides or, more rarely, of Grimmia ericoides. Throughout this carpet 

 a few phanerogams occur, and with some other mosses and lichens 

 break the monotony, without being very conspicuous. The forma- 

 tion developed in this manner is found on the more elevated moun- 

 tain-plateaux, never below 400 m., provided the conditions for its 

 existence are present. The edaphic conditions most needful, in ad- 

 dition to the climatic ones, are a flat surface or a gentle slope 

 with a soil not excessively wet and a fair amount of shelter from 

 storm. 



The typical Grimmia-heath never occupies extensive areas on 

 the Islands, for the simple reason that few large areas suitable for 

 its development exist at altitudes of 400 — 500 m. 



The formation appears on all the larger islands, but attains its 



64* 



