827 



zosterifoUa, hthmoplea sphærophora, Hinmnthalia lorea, which is, 

 however, most likely hapaxanthic (see 8, p. 480), several species of 

 Ectocarpus and others; of green algæ may be mentioned several 

 species of Entcromorpha , Monostroma Greuillei and M. undiilatiim, 

 (whereas M. fiisciim, as pointed out by Ro sen vinge (p. 238) can 

 most likely live for more than one year), the species of Ulothrix, 

 Acrochæte repens, Bolbocoleon piliferum, Pringsheimia scutata, Uro- 

 spora mirabilis and U. Wormskioldii , Codiolum , Cladophora sericea 

 and Cl. gracilis, Acrosiphonia (-?) and others. 



Several of these species are certainly capable of producing more 

 than one generation in a year; as pointed out by Gran (37, p. 9), 

 those short-lived species (e. g. Porphyra umbilicalis, forms of Entcro- 

 morpha intestinalis, species of Ulothrix, possibly Monostroma Greuillei 

 etc.) only belong to the littoral region, the reason probably being 

 that only algæ growing in full daylight are able to go through all 

 stages of development in so short a time; we may likevsåse sup- 

 pose with some reason that the rapid development of the short-lived 

 algæ, as pointed out by Gran, is an adaptation to the often very 

 unfavourable biological conditions under which the littoral algæ live, 

 especially those growing at the highest level, just where the short- 

 lived algæ are met with. 



With regard to Greenland, Rosen vinge has remarked that 

 the low temperature of the sea prolongs the lifetime of many an- 

 nual algæ, and just in the same way the low summer temperature 

 of the Færoes, together probably with the small amount of direct 

 sunshine, has a preserving and prolonging influence on the annual 

 algæ of spring and summer. For example, a great many species, 

 which are only found towards the end of winter and during the 

 months of spring in the Danish and adjacent seas, grow luxuriantly 

 during the whole summer in the Færoes. 



Thus Porphyra umbilicalis forms well developed associations dur- 

 ing the whole summer, whilst, according to Kjellman, it only forms 

 associations in winter on the coasts of Rohuslån. Vigorous specimens 

 of Diimontia fdiformis, which in the Danish seas grows in spring and 

 beginning of summer, are found during the whole summer on the Fær- 

 oese coasts. Fuciis inflatns f. disticha is found in the summer at Hauge- 

 sund according to a report from Mr. Norum; but the specimens are 

 only badly developed at that season, though vigorous when found 

 during the months of December to March. At the Færoes, however, it 



Botany of the Færoes. 53 



