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continuous, almost pure growths on rocks (Ramalina-he\\.) on the 

 cliffs of Bornholm. Species of Roccella appear to form similar carpets 

 on the cliffs of the suh-tropical and perhaps tropical regions. 



Of Fruticose rock-lichens the following are found in Iceland : - 



Alectoria ochroleuca. 

 Coenogonium ebeneum. 

 Ephebe pubescens. 

 Lichina confinis. 

 Racodium rupestre. 

 Ramalina scopulorum. 

 subfarinacea. 



Sphaerophorus coralloides (?). 



fragilis (?). 

 Stereocaulon coralloides i . 



denudatum. 



cvolutum. 

 Usnea melaxantha. 



With regard to these it should be remarked that it is some- 

 what doubtful how far Racodium and Coenogonium should, on the 

 whole, be reckoned among the fruticose lichens : they have a thread- 

 shaped, somewhat procumbent-ascending thallus. Also a query has 

 been placed against several of the other species, to indicate that it is 

 doubtful whether they are true rock-lichens occurring on bare rock 

 because, at any rate when older, they are rarely, in fact very rarely, 

 attached to the rocky substratum. 



5. SYNOPSIS OF THE CHIEF BIOLOGICAL CONDITIONS 

 OF THE LICHENS OF ICELAND. 



