827 



zoster if olia , Isthmoplea sphcerophora , Himanthalia lorea, which is, 

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

 Ectocarpiis and others; of green algae may be mentioned several 

 species of Enteromorpha, Monostroma Greuillei and M. undiilaliim, 

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

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

 Acrocluvte repens, Bolbocoleon piliferum, Pringsheimia sciitata, Uro- 

 spora mirabilis and U. Wormskioldii, Codiolum, Cladophora sericea 

 and CI. gracilis, Acrosiphonia (9) 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. Porphijra umbilicalis, forms of Entero- 

 morpha intestinalis, species of Ulothrix, possibly Monostroma Grevillei 

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

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

 stages of development in so short a time; w^e may likewise sup- 

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

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

 unfavourable biological conditions under which tlie littoral algae live, 

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

 lived algae are met with. 



With regard to Greenland, Rosen vinge has remarked that 

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

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

 of the Faeroes, together probably with tlie small amount of direct 

 sunshine, has a preserving and prolonging influence on the annual 

 algae 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 wiiole summer in the Faeroes. 



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 Bohuslan. Vigorous specimens 

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

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

 oese coasts. Fucus in flatus 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 Faeroes, however, it 



Botany of the Faeroes. 53 



