CHAPTER IX. 



SEAWEEDS AND THE WATER-FLORA. 



The surface of the earth is generally covered by a 

 nearly continuous green carpet of vegetation, which 

 differs greatly in character according to the soil, and to 

 exposure. This green covering is even continued 

 through fresh or salt water ; for the vegetation simply 

 alters its character as soon as it is influenced by 

 moisture ; and a new flora appears, which extends 

 through and under the water, rendering the barren 

 waves anything but lifeless and useless in the world's 

 economy. 



This water-flora may be divided for convenience into 

 three groups, (i) The Plankton^ the free swimming or 

 floating vegetation which occupies the surface, and goes 

 down to a depth of 2-3 metres. As a rule the Plankton 

 consists of very minute Algae or Seaweeds, which are 

 only visible with a microscope; but sometimes there are 

 also large Seaweeds, such as Sargasso Weed, or flowering 

 plants like the Duckweed {Leimia)^ and the Florida 

 Hyacinth. (2) The plants which cover the bottom of 

 fresh-water lochs, rivers, and streams, and others which 

 form the submerged flora of the coast-line, and are 

 attached to the rocks, shingle, or other soils below 

 the sea. These also are chiefly Seaweeds or Algae. 

 (3) The transitional series, which includes many plants 

 found in marshes, on mud, and by the seaside. These 



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