970 



piaces where the watcr-supply is fairly abundant. As a rnie, both 

 mosses and lichens receive Iheir main supply of water from atmos- 

 pheric sources. 



The lichens cover the clilTs almost entirely, and give rise to a 

 series of colours ranging from nearly black to nearly white, with a 

 predominance of greyish tints of almost every conceivable hue (see 

 Fig. 182). Crustaceous lichens are most common, especially the 

 following genera: Lecanora (L. tartarea, L. atra, etc), Lecidea, Pla- 

 codiiim, Sqiiamaria (S. gelida) and Biiellia; foliaceous lichens also 

 occur among the dominant species, the commoner being, Parmelia 

 saxatilis, Xanthoria parietina var. aiireola and Gyrophora(G.cylindrica). 

 The following lithophile mosses are the most frequent: Andreaea pe- 

 trophila and Grimmia spp. (G. fasciciilaris, G. acicularis, G. heterosticha, 

 G. apocarpa, etc). To these might be added many other mosses 

 which occur wherever shelter and other conditions are favourable, 

 especially on isolated boulders and stones, and on talus-slips (Ur). 



The lithophyte vegetation of isolated blocks constitutes a special 

 association: the lithophyte association of the isolated stones 

 and boulders, and is different from the lithophyte association 

 of the solid cliffs. The characteristic species of isolated boulders 

 are Antitrichia cnrtipendiila and Isothecium myosuroides, also the 

 rare Hedwigia albicans^. 



^ C. Jensen has kindly given me the following complete list of lithophile 

 mosses on the Færoes: 



Frullania fragilifolia Grimmia pulvinata 



— Jackii — funalis 

 Lejeunea calcarea — torquata 



Radula commutata — maritima (coast cliffs) 



Porella Thuja — apocarpa 



— rivularis — gracilis 

 Hygrobiella laxifolia — alpicola v. rivularis 

 Metzgeria furcata Andreaea petrophila 

 Pottia crinita Hypnum rusciforme 

 Blindia acuta — viride 



Weissia maritima (coast cliffs) Lesquereuxia patens 



— americana Isothecium myosuroides 

 Orthotrichum rupestre — viviparum 



Zj'godon viridissimus v. rupestris Heterocladium heteropterum 



Glyphomitrium polyphyllum Stereodon resupinatum 



— Daviesii Porotrichum alopecurum 

 Grimmia fascicularis Fontinalis antipyretica \ Water- 



— heterosticha — gracilis / lithophytes 



— affinis Antitrichia curtipendiila 



— acicularis Hedwigia albicans. 



— trichophylla 



