SECT. n. ZONES OF MARINE VEGETATION. 259 



the Channels ; while the northern flora is confined to 

 the Scottish seas, and the adjacent coasts of England and 

 Ireland. The second British zone begins at low water 

 mark, and extends below it to a depth of from seven to 

 fifteen fathoms. It contains the great tangle sea weeds 

 or marine forests mixed with fuci, and is the abode of a 

 host of animals. A coral-like sea weed is the last plant 

 of this zone and the lowest in these seas, where it does 

 not extend below the depth of sixty fathoms ; but in the 

 Mediterranean it is found at seventy or eighty fathoms, 

 and is the lowest plant in that sea. The same law 

 prevails in the Bay of Biscay, where one set of sea weeds 

 is never found lower than twenty feet below the surface, 

 another only in the zone between five and thirty feet, 

 another between fifteen and thirty-five feet. In these two 

 last zones they are most numerous ; at a greater depth 

 the kinds continue to vary, but their numbers decrease. 

 The distribution in the .ZEgean sea was found by Pro- 

 fessor E. Forbes to be perfectly similar, only that 

 the vegetation is different and extends to a greater 

 depth in the Mediterranean than in more northern 

 seas. He also observed that sea weeds growing near the 

 surface are more limited in their distribution than those 

 that grow lower down, and that with regard to vege- 

 tation, depth corresponds with latitude, as height does 

 on land. Thus the flora at great depths in warm seas 

 is represented by kindred forms in higher latitudes. 

 There is every reason to believe that the same laws of 

 distribution prevail not only throughout the ocean, but 

 in every sea. 



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