8oo ZONES AND REGIONS [Pt. Ill, Sect. V 



exceeds in size all other plants, attaining a length of 300 meters ; but it 

 occurs again in the northern Pacific, on the American coast (Fig. 4H9). 

 A second species of Macrocystis, M. angustifolia, Bory, is confined to the 

 temperate west coast of South America. 



v. THE ARCTIC BENTHOS. 



The algal flora of the Arctic Ocean is poor in species, and covers smaller 

 areas than in more southern seas ; on the other hand, it exceeds that of all 

 other seas, except the Antarctic, in the dimensions of a great part of its 

 species, and precisely of those that grow socially and form the main mass of 

 the vegetation at all seasons of the year. Kjellman 1 , whom we have 

 chiefly to thank for a knowledge of the Arctic algal vegetation, says: 'We 

 stand as it were before an insoluble enigma when our dredge- net brings 

 from the depths of the sea these plants whose robustness testifies to their 

 unrestrained vital vigour, whilst a massive sheet of ice covers the sea and 

 the temperature of the air is extremely low, and whilst nocturnal darkness 

 reigns even at midday.' This flora is principally composed of Phaeophyceae 

 (Laminarieae, Fucaceae) and Florideae (particularly Corallinaceae), whereas 

 the Chlorophyceae are few, and, when compared with those of southern seas, 

 poorly developed. The topographical distribution is limited to a smaller 

 variety of habitats than on temperate coasts. Sandy and muddy soils, 

 except on scattered stones, are bare of vegetation ; there are no sea-grasses. 



The emerging belt is occupied by vegetation in subarctic seas only, for 

 instance on the coast of Norway and the west coast of Greenland. Else- 

 where it possesses either no vegetation or only a poor one, because the masses 

 of ice, which the breakers and tides keep in continual motion, arrest all 

 plant-growth by shearing the rocks. Wherever the emerging belt is 

 not exposed to the destructive action of ice, it bears chiefly Fucaceae, 

 as in temperate seas. The subarctic seas may even be termed Fucaceae- 

 seas. The real Arctic Ocean, however, is the sea of Laminariaceae. Here, 

 at depths of 3-10 fathoms, species of Alaria (Fig. 490) and Laminaria 

 build up extensive formations in the shade of which photophobous forms 

 thrive. In places, instead of the Laminariaceae, there appear broad 

 banks of Corallinaceae, particularly composed of species of Lithothamnion 

 (Fig. 491) and Lithophyllum, which attain relatively large dimensions. 

 The poverty of the flora as regards Chlorophyceae is due to the weak 

 illumination, as the members of this group are generally photophilous. 



The lower limit of the photic region appears to lie at a depth of 20 

 fathoms. The dysphotic region in the Norwegian polar sea contains no 

 macrophytes, but at Spitzbergen Kjellman has found Delesseria sinuosa 

 at a depth of 85 fathoms, Ptilota pectinata in Smeerenberg Bay at 150 



1 Kjellman, II. 



