700 ZONES OF MARINE VEGETATION. 



similar to that which high mountains have on land plants. Some 

 species, as the Laminarise, are confined to the colder regions of the 

 sea, whUe others, as the Sargassa, are only found where the mean 

 temperature is considerable. The colour of Algae may be regarded 

 as being in a measure indicative of their depth of growth, the Algse of 

 green colour being generally found either in fresh water or in the shal- 

 lower parts of the sea ; the olive-coloured Algae abound most between 

 tide-marks ; those of a red colour occur chiefly in the deep and dark 

 parts of the sea. 



Marine vegetation is found to vary both in its horizontal and 

 vertical range. This difference is less decided than that which is 

 observable amongst land plants, owing probably to the greater uni- 

 formity of the ocean's temperature. The ocean has been divided into 

 the following provinces of marine vegetation: — 1. The Northern 

 Ocean, from the Pole to the 60th parallel of north latitude. 2. The 

 North Atlantic, between the 60th and 40th parallels, the province of 

 the species of Fucus proper. 3. The Mediterranean, which is a sub- 

 region of the warmer temperate zone of the Atlantic, lying between 

 the 40th and 23d northern parallels. 4. The tropical Atlantic, in 

 which Sargassum abounds. 5. The Antarctic American regions from 

 Chili to Cape Horn, and the whole circum-polar ocean south of 50° of 

 latitude. 6. The Australian and New Zealand province. 7. The 

 Indian Ocean and Ked Sea. 8. The Japan and China seas, besides 

 certain provinces in the Pacific. 



Forbes remarks of the vertical range, that one great marine zone 

 lies between high and low water mark, varying in species according to 

 the nature of the coast. This zone is generally uniform throughout 

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

 and extends to a depth of 7 to 15 fathoms. The first of these, or the 

 littoral zone, has been divided into sub-regions, in which certain marine 

 species are found to prevail. 1. The sub-region of Fucus canalicu- 

 latus. 2. The sub-region of Lichina. 3. The sub-region of Fucus 

 articulatus, F. nodosus, and Corallina officinalis. 4. The sub-region 

 of Fucus serratus. The second or Laminarian zone includes the great 

 Tangle sea-weeds and deep-water Fuci. The lowest forms of marine 

 vegetation are alone met with in the deepest waters. 



Marine vegetation is equally various in its latitudinal or horizontal 

 range. In the North Sea and the British Channel Chorda Filum is 

 found to constitute beds of 15 to 20 mUes in length, and about 600 

 feet in breadth. Sargassum bacciferum constitutes the Grulf-weed of 

 the Atlantic. The Sargasso sea occupies the eddy caused by the 

 revolution of the Atlantic current, and extends over a space of 260,000 

 square mUes. There are two principal banks of Gulf-weed ; — one, the 

 largest, extending from 25° to 36° of north latitude, and a little west 

 of the meridian of Fayal ; the other, a short way west of the Bahamas, 



