116 FORESTRY OF NORWAY. 



of the vegetation of the polar seas, and are particularly 

 abundant in the colder temperate zone. The green colour 

 is characteristic of those algue which grow either in fresh 

 water or in the shallower parts of the sea ; the olive- 

 coloured algae are most abundant between the tide-marks; 

 while the red-coloured species occur chiefly in the deeper 

 and darker parts of the sea. 



' As regards perpendicular direction, Forbes remarks, that 

 one great marine zone lies between high and low water- 

 marks, and varies in species according to the kind of coast, 

 but exhibits similar phenomena throughout the northern 

 hemisphere. A second zone begins at low water-mark, and 

 extends to a depth of from 7 to 15 fathoms. This is the 

 region of the larger laminarias and other fuci. Marine 

 vegetation, including the lower forms, extends to about 50 

 fathoms in the British seas, to 70, 80, or 100, in the Medi- 

 terranean and the ^Egean sea. Ordinary algae, however, 

 seem scarcely to exist below 50 fathoms. Diatomaceae 

 exist in the deep abysses of the ocean and nullipora and 

 corallines increase as other algae diminish, until they 

 characterise a zone of depth where they form the whole 

 obvious vegetation. . . . . . 



'The vertical range of terrestrial vegetation has also 

 been divided into similar zones in altitude. The relation 

 is called hypsometrical. As we ascend from the plain to 

 the top of a mountain we pass through different belts 

 of plants, to such zones of elevation is of vegetation, 

 the extent and variety of which differ in different 

 countries. When Tournefort ascended Mount Ararat 

 he was struck with the circumstance, that, as he left 

 the low ground at the base of the mountain, he passed 

 through a series of belts, which reminded him of the 

 countries he had passed through in travelling from the 

 south to the north of Europe. At the base the flora was 

 that of the west of Asia ; as he ascended higher he 

 reached the flora of the countries on the north of the 

 Mediterranean, then that of northern Europe, and when 

 he reached the summit he found the Lapland plants. 



