.?r)8 .loiis. uovi; i'i;ri;i<si:N 



intliK'iu't's ils vcf^clalion. 1 hnve visilcd Ihi' lilloial nioadow at IJorg 

 espeoially relenod lo by .lonsson, aiid, likc liini, I find llial V<ni- 

 chcria si)lHvrosi)oni is tlie most widespread species ol" alj^a iii tlie 

 nieadow ilself and parlicularly »\vliere tlie carpet ol' (iraniineæ 

 abutled on the elay, which was partly overgroNvn ^vith 7'/7V//or/j//i 

 marilimuiU'i. I lound lliat, especially on the clayey hanks ol the 

 stream nicntioncd at p. 4 (H. Jonsson l.c), it formed very lai-^e 

 tufted growths (Fig. 1). Among its filaments and, I think, covering 

 the whole surface of the meadow, there weie numerous species ol' 

 Dialoms, which can liardly, however, he assumed lo Ihrive jjarti- 

 cularly well on the surlace. More probahly they must be i'egarded 

 as halophilous species. Hence I shall make no f'urther mention of 

 them here. On littoral meadows there will likewise occur washed 

 up marine algæ, especially green algæ, in small depressions. 



2. Rocks and Loose Stones. 



The bed-rocks of Iceland consisls for the most part of basalt 

 and palagonite-breccia. There is no essential dilTerence in the chem- 

 ical composition of these two kinds of rock, the breccia being formed 

 of fragments of basalt mixed with volcanic tulT and other volcanic 

 rocks of more recent date. There is, however, a ditlerence in the 

 physical composition, the basalt being much more compact than 

 the breccia. The basalt contains some calcium, but bound in such 

 a way that it is not easily soluble, and it may therefore be supposed 

 that the piants that grow on it do not derivc much benefit from 

 its content of calcium. Finally, a considerable part of the surface 

 of the island is covered by lava-streams of earlier or later date. 

 As regards the algal vegetation on these, which is on the whole very 

 sparse, I can only give liltle information, as will appear from the 

 succeeding part. 



In Nature rocks will no doubt always contain a greater or less 

 amount of moisture which may be derived directly from the rain 

 partly absorbed by the rock. Another part of the rain runs down 

 the rock, especially in cerlain j)laces where furrows make a way 

 for il. lii many piaces a considerable amount ol" waler is produccd 

 throughout the summer by Ihe snow melting on the highest peaks, 

 and finally, in many piaces, water issues from the mounlain sides 

 in smaller or larger springs. Thus there will often be found piaces 

 in the rocks, particularly the basaltic rocks, where the moislure is 

 considerable. For the algal vegetation the amount of moisture is 



