V. THE VERTICAL DISTRIBUTION 

 OE THE LICHENS. 



Thoroddsen, in vol. I of this work, has given an account of the 

 little which is, as yet, known as regards the vertical distribution 

 of the phanerogams. It must unfortunately be admitted, that our 

 knowledge of the lichens is, in this respect, still more scanty. The 

 object which it was desirable to attain, viz., a thorough knowledge 

 of the occurrence of each single species, from sea-level upwards on 

 the mountains, is still unattained, but something is known on the 

 subject. 



It is not known with certainty, as regards any single species, 

 how far it has any other upper limit on the mountains, than the 

 snow-line, with the sole exception of the decidedly maritime species 

 Verrucaria maura and Lichina confmis, which are connected only 

 with localities washed by the spray of the waves. 



Nor is it known with any certainty as regards a single species, 

 how far it has any other lower limit than the sea-level; several 

 species are, however, known, regarding which it is, at any rate, 

 probable that they are associated with cold mountain heights, and 

 avoid the milder climate of the low land. This is the case, for in- 

 stance, with Usnea melaxantha and Solorina crocea, which hardly 

 ever descend anywhere into the lowlands, without its being possible 

 to give a tolerably definite lower limit. 



In order, however, to give a small contribution to our knowledge 

 regarding this point, I shall proceed to enumerate the lichens found 

 in a few localities situated on high ground : 



On Hliflarfjall, which is mentioned under the rock-lichen-asso- 

 ciations, under "Liparite," there grows a scanty vegetation consisting 

 of the following species: 



Hhizocarpon geographicum. Gyrophora cylindrica. 

 Lecanora polytropa. arctica. 



alpina. hyperborea. 



Gyrophora erosa. Parmelia lanata. 



