CHAPTER V 



A WORLD IN THE WATER 



Crowded as is the earth with vegetation, we 

 shall find an even more extensive collection of 

 plants in the waters of the world. In the 

 element which probably first sustained the 

 beginnings of vital matter, there are still a 

 myriad forms of plant life, ranging from the 

 green slime, so often to be seen in stagnant 

 pools, to the large branched marine weeds. 

 Gathered together under the name algse, there 

 are a prodigious variety of plants, to sup- 

 ply a detailed description of which would be 

 the labour of a lifetime. All these organisms 

 are of comparatively simple structure, many 

 of them consisting of but a single cell, whilst 

 even the most elaborate are largely an aggrega- 

 tion of cellular tissue. Nearly all the forms 

 are more or less aquatic in habit, although it 

 must not be understood that they all exist in 

 water. A large number of algae are able to live 



upon the surface of rocks and trees in damp 



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