'^C^i JOHS. BOYE PETKHSKN 



horcdlis. aiul on llic lidyc bolwot'n IsaljiMAui' ;iii(l IhiU'vri, clost- lo 

 llu' liij^lu'sl bearon , on loose hlocUs ol" lava, I louiid several line 

 green giowihs ol" Prnsiola crispn willi a lillle Ilonnidiiini fhucidiuu 

 antl a nninber ol' Dialoni species, the coninionesl ol' whicli was 

 Pinnularid horenlis (sample 2().S). Il is veiv peculiai' thai such a ricli 

 algal vegelalion ean l)e l'oniui in Uiese two, evidenlly verv dry, 

 piaces, (jnite open lo Ihe witul. 



Stenes near llic shore have no douhl a spccial associalion ol' 

 algie. As an exaniple 1 ean only nienlion a laii^i' slone near llie 

 shoie on Heiiiiaey wliicli was covered \vitli a green pulveridenl 

 layer of Pseudendocloninm submarinum and Prnsiola sp. 



e. Bild Cli/fs (406, 407, 408, 409, 410). 



The slcep roclvy walls l'acing Ihe sea which are so common in 

 Iceland are generally inhahiled by connllcss seabirds and are then 

 cailed bird clill's. I have only been able to examine one such clilT, 

 on Heimaey (Veslmannaeyiar). Rising steeply from the low neck ol' 

 sand connecting Heimaklellur with the rest of the Island, it forms 

 a grassy slope to about 50 melres' height, and thence rises perpen- 

 dicularly to double the height (Fig. 2). On the small ledges and in 

 the cracks in the perpendicular \vall the birds build, and their 

 droppings manure the rocks and the grassy slope below. The samples 

 of algæ were gathered at the bottom of the perpendicular wall, Ihus 

 at a height of about 50 m. As might have been expected, some 

 nilroj)hiIous species were l'ound,viz. Prasiola crispa, P. fiirfuracea. 

 Phoriiudiiim nntnmnale, 1^. snbfuscmn, Nauicnla Atomiis, Nanicnia 

 mulica f. Cohnii and /". minima. The presence of some brackish 

 water species must presumably be ascribed to the j)roximity of the 

 sea. These were: Phizoclonium lapponicnm, Vauchcria sijnandra, 

 Xaniciila cincla, N. (jregaria, Nitzschin vitrea v. s(dinarum. Furlher 

 a series of indilferent species were found, such as Desmococcus nid- 

 (jaris. Achnanfhcs coarclala, A. kaueolaia, Caloneis fasciaia, Hantzschia 

 amjihioxi/s, Nanicnia contenta, N. perpnsilla, \. pnsilla, Xitzschia debilis, 

 N. Sif/ma v. CJansii, Pinnnlaria intermedia , P. parva v. Lagerstcdlii 

 f. inU'irnjda. 



3. The Algal Vegetation round Hot Springs. 



IIol springs are found in nearly all parts of the island. A very 

 peculiar algal vegetation occurs in llu- water itself and olien sj)rea(ls 

 to the surroundings of the spring where il is not direclly welled 



