INTRODUCTION. 
I 1913, after deliberation with Professor E. Warming, I made 
a journey to Iceland to investigate the island lichenologically, 
as far as this could be 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 
