NATURAL HISTORY STUDIES 



It should be noticed, however, that considerable 

 evidence is accumulating in support of the view that 

 the minute floating plants are even more important 

 in their death than in their life. For when they are 

 killed by changes of temperature and the like, or 

 when they reach the end of their natural tether, 

 they add to the valuable organic debris which 

 remains in suspension in the water or sinks to the 

 floor of the sea. To this accumulation of organic 

 debris very important contributions are also made 

 from the shore belt of seaweed and sea-grass. 

 Indeed, recent investigations by two Danish natural- 

 ists, Petersen and Jensen, show that the organic 

 matter of the sea-floor in the sheltered waters of 

 fjords and bays is mainly due not to the sinking 

 down of the minute surface creatures, but to the 

 detritus of the sea-grass and its associates in shallow 

 water. This is of great practical importance, since 

 it is in man's hands to cultivate, if need be, the 

 littoral vegetation, and thus cast bread upon the 

 waters, to be gathered again after many days. 



Sea -Meadows 



In the relatively shallow Danish waters the sea- 

 bottom consists of vast plains of sand, mud, or clay, 

 with transitions between these ; and almost every- 

 where except in the deepest and calmest hollows 

 there are scattered stones of all sizes carrying a 

 distinctive population of their own. From the 

 shore to a depth of two or three fathoms are the 

 meadows of the sea-grass, with true roots and flowers 

 and very long ribbon-like leaves, familiar as a pack- 



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