INTRODUCTION. 



IN 1913, after deliberation with Professor E. Warming, I made 

 a journey to Iceland to investigate the island lichenologically, 

 as far as this could he done during the course of one summer. I 

 had visited the island once before, (1906) and had become interested 

 in its lichen-vegetation, which impressed me as presenting many 

 features of great interest. At that time I had, however, very little 

 opportunity of making investigations, therefore I eagerly seized the 

 opportunity of investigating the lichens, which offered itself in 1913. 

 Already, before this last journey, I had studied the lichen-vegetation 

 more thoroughly in the different plant-associations of Denmark, and 

 had published my investigations on this subject in 1908; afterwards 

 (in the early summer of 1913) I published my "Forberedende Under- 

 sogelser til en almindelig Likenokologi" ("Introductory Investigations 

 concerning a general Lichen-Ecology"), and was therefore now highly 

 interested in extending my investigations to a country, which was 

 not situated in the same climatic zone as Denmark, because I might 

 expect to find there essentially different vegetational and floral con- 

 ditions; and I was not disappointed with regard to this point. I 

 made collections and notes as assiduously as the somewhat dif- 

 ficult conditions of travelling permitted, but I am sorry to say 

 that I must admit, in my own case and probably in that of 

 others also, that Iceland is too large to survey fully during one 

 summer's travel. 



However, I hope, and also believe, that the descriptions I have 

 been able to give below, will not be altered essentially by investiga- 

 tions, which may possibly be made by future travellers. 



The districts which I investigated most thoroughly were those 



