737 



gans, Rhodochorlon Rothii, Pelvetia canaliculata, Ceramiiim acantho- 

 notiim, Prasiola crispa *marina, Prasiola furfuracea and Prasiola stipi- 

 tata. There are moreover several littoral algæ which grow but rarely 

 in littoral pools, and when found there, are only imperfectly devel- 

 oped. In littoral pools belween Thorshavn and Hojvig I have often 

 found e. g. Gigartinn mamillosa, which was hardly more than one 

 inch long. Species of Fiicus, e. g. Fucus spiralis and Fiiciis inflatus 

 become paler in the littoral pools, the thailus likewise becoming 

 thinner, and the piants are relatively small. This is the case \vilh 

 several littoral algæ. Evidently, some of them do not thrive when 

 they are constantly in water; it seems as if they require to be laid 

 bare for a shorter or longer space of time. Ros en vinge is also 

 very probably right, when he supposes (71, p. 191) that certain lit- 

 toral algæ perform part of their work of assimilation at low tide. 



In the highest pools with their more or less fresh, luke-warm, 

 and often half polluted water, where circumstances are very un- 

 favourable to the algæ, only an Enteromorpha-xegetai'ion is found, 

 mainly consisting of forms of E. intestinalis. It is the only alga which 

 can live imder such unfavourable circumstances. It may be found 

 far above the level of the sea, e. g. at Bosdalafos on Vaago where 

 it grows luxuriantly in small pools which are more or less inundated 

 by small fresh water streams. In this connection it may also be 

 mentioned, that I have found forms of Enteromorpha intestinalis at 

 a height of about 600 feet (cf. 7, p. 242—245 and 8, p. 492). 



A little lower, where the water is cleaner, other forms of En- 

 teromorpha occur, e. g. var. compressa, var. prolifera and species of 

 Cladophora e. g. C. gracilis and C. sericea. Hildenhrandia gradually 

 gives a reddish hue to the sides of the pools, and several brown 

 algæ appear, e. g. forms of Fucus spiralis and Fucus inflatus f. line- 

 aris; the latter has hitherto only been found at Famien on Sydero. 

 Forms of Ectocarpus litoralis, Scytosiphon lomentarius, Phyllitis fascia 

 and others moreover occur. Still farther down, where the water 

 is regularly renewed at high tide, large, uneven brown crusts of 

 Ralfsia verrucosa are found intermingled with the red Hilden- 

 hrandia. The bottom may also be covered by a dense matting of 

 Corallina officinalis, sometimes mingled with Phijmatolithon poly- 

 morphum. On Corallina one may also find crusts of Dermatolithon 

 macrocarpum f. Corallinæ. Mingled with Corallina, several different 

 algæ may be found e. g. Dumontia filiformis, Rhodoniela lycopodi- 

 oides, Polysiphonia urceolata and P. Brodiæi, Lonientaria clavellosa. 



