INS OLAl (1AI.L0E 



where along the sides of the fjords. Owing to their great water- 

 contents they are always devoid of lichens. 



Grimmia-heaths are found, as mentioned, at all altitudes right 

 up to the sno\v-line, but differ somewhat according to the altitude. 



The substratum which supports the f//'//mm'a-carpet is some- 

 times solid rock, sometimes loose soil. Mv own observations are 



KI 



derived almost exclusively from carpets upon lava. 



On mountain heights (fell -fields) the carpets are often small 

 in extent, but further down in the low land they may cover large 

 continuous tracts. 



The plant-carpet is a few centimetres high and the moss-shoots 

 stand erect. Whatever may be the nature of the deeper-lying sub- 

 stratum, at the bottom of the carpet there is always found, as a 

 matter of course, a peat-formation consisting of the dead remains 

 of the mosses, as soon as the moss-covering is only a few years 

 old. The deeper-lying soil is evidently of no direct importance, or 

 concern to the lichens; they are connected with the peat and the 

 dust-particles, which always occur on it, and amongst the mosses. 



With regard to the amount of w r ater contained amongst the 

 mosses, very little is mentioned in the literature. It may, however, 

 be taken for granted that all Grnmm'a-vegetation in Iceland is dry 

 enough to bear lichens. My own observations show this distinctly 

 enough. For the rest, there is, as usual, the great defect, that we 

 h:ive no fixed method to indicate the degree of dampness of the 

 plant-association, as far as emergent associations are concerned. We 

 are constantly reduced to the entirely relative, and consequently 

 almost useless terms, "dry," "damp," etc., without any fixed state- 

 ment as regards measured amount. 



Jonsson states that there is an essential difference in the ac- 

 companying phanerogams in high and in low land, in that only a 

 lew occur on the rocky flat, whilst they are found far more numer- 

 ously further down. He states, in addition, as a general fact, that 

 lichens are found more abundantly in the (iV/m/ma-carpets of the 

 rocky flat, than in those of the low land. How far this is quite 

 right can only be proved by frequency-numbers, and statements of 

 mass-occurrences (in weight), and such are not found in sufficient 

 numbers. I must, however, say that Jonsson's statement sounds 

 \ery reasonable, and is supported by Hesse Ibo. It can undoubtedly 

 be explained by the fact that the climatic conditions are more un- 

 favourable to the mosses in the high land, and relatively more 



