THE OCEAN AND THE LAND 



On land there is vegetation everywhere except in the most 

 arid regions, and even there a heavy rain is immediately fol- 

 lowed by the appearance of plants of many kinds. The plants 

 are always the most conspicuous living features of every land- 

 scape; but they grow only on the surface of the land, rooted 

 in the soil or, more rarely, attached to some support or floating 

 in the water. 



In the open sea no plants are ever visible save for an occa- 

 sional dying rockweed torn from its moorings, though some- 

 times streaks and clouds indicate masses of diatoms or other 

 minute plants individually invisible to the unaided eye. The 

 visible life of the sea is wholly animal; but the microscopic 

 plants, all of which freely drift about, exist in incredible num- 

 bers and occupy a broad stratum reaching a maximum of about 

 650 feet in thickness in the clearest waters of the tropic seas, 

 but decreasing to a much less thickness north and south where 

 the water is less transparent and where the light is less. 



Very few animals feed directly upon the sea plants, and of 

 these only the minute crustaceans are of first importance. 

 These, possessed of only feeble swimming powers, drift aimlessly 

 about and may be said to furnish the chief, though a purely 

 secondary, basis of marine life; though animals, they are to the 

 economics of the ocean what the green plants are to the eco- 

 nomics of the land. 



In contrast to land animals, most of the smaller and many of 

 the fairly large sea animals, such as the jelly-fishes and the 

 younger stages of such fishes as the ribbon- fishes and the eels, 

 are more or less transparent, some quite so, looking like glass 

 models of themselves. 



195 



