932 



the vegetation limited to fissures and small ledges, for the faces of 

 the Cliffs themselves become covered with cryptogamic piants, in- 

 cluding lichens, mosses and algæ. 



The cliff vegetation as a whole will be dealt with more com- 

 prehensively later, but this is the place to consider that particular 

 form of cliff-vegetation which belongs to the cliffs facing the sea. 

 Here the sea-water often lashes up in spray over the piants, and 

 this in conjunction with the salt-charged and vapour-laden atmos- 

 phere, produces special conditions which favour halophile species 

 and drive others away. 



In analysing the cliff-vegetation later, reasons will be given for 

 dividing the piants growing on the cliffs into Lit hop bytes and 

 Chomophytes. It will suffice for the present to defme the two 

 categories. Lithophytes are the piants which grow on the surface of 

 the cliff proper; cryptogams alone are represented in our temperate 

 countries. Chomophytes, on the other hånd, inhabit fissures and 

 small terraces among the cliffs where fine-soil has gathered. 



A helt of coast-cliff plant-formation is found all round the 

 coasts of the Islands. Downwards it merges into the Verrucaria 

 formation and the littoral algæ-formations, and upwards it is gra- 

 dually transformed into the ordinary cliff-vegetation. 



The lithophytes belonging to the coast-cliff formation are lichens 

 and mosses; the algæ becoming of minor importance as soon as 

 we pass above the zone liable to occasional inundation by sea- 

 water. 



The transition-formation between the submerged vegetation and 

 the aérial vegetation is the Verrucaria formation (see F. Bor- 

 gesen 1905, pp. 711 — 718, Hildenbrandia-Formation, Chlorophyceæ- 

 Formation and Porphyra-Association), the species of which form a 

 zone on the cliffs where sea-water occasionally lashes over. This 

 formation has been named the »supralittoral« region by E. W ar- 

 mi ng (cfr. Porsild and Simmons 1904, p. 173), a name which has 

 also been used by Lorenz (1863, p. 193), but not with quite the 

 same meaning. 



Above the Verrucaria formation we meet a number of other 

 lichens, characteristic of the coast-cliff' formation, the most important 

 and typical species are: Ramalina scopnlorum and Lichina confinis 

 (fruticose lichens), Physcia aqiiila and the rare Ph. ciliaris saxicola 

 (foliaceous lichens), and Placodia, Verriicariae, etc. (crustaceous li- 

 chens). Along with the lichens two species of mosses are very 



