SEA-MEADOWS 89 



nence to the part played by the down-sinking of 

 minute (Plankton) organisms killed or worn out 

 at the surface, and there is no reason to disregard 

 this factor. It is probably of fundamental impor- 

 tance for the immense areas which may be called 

 more or less abyssal, for these, being far beyond the 

 limit of illumination, cannot have any autoch- 

 thonous plants able by photo-synthesis to build up 

 complex carbon-compounds from simple constitu- 

 ents in the water. But in the relatively shallow 

 illumined waters near shore the economy is different, 

 and it seems that great importance must be ascribed 

 to what may be called " sea-meadows/' the dense 

 growths of sea-grass (Zostera), a veritable flower- 

 ing plant, and of attached seaweeds, large and small, 

 from the great bladder-wracks and laminarians to 

 the small tufts of the palatable " carrageen " or 

 Irish moss. Without depreciating the role of the 

 minute Plankton organisms which may sink down 

 from the surface, we wish to state the case which 

 Professor C. G. Joh. Petersen has recently presented 

 in an interesting report (1918) to the Danish Board 

 of Agriculture, which at any rate shifts the emphasis 

 to the sea-meadows. It need hardly be said that 

 Danish waters are much less heterogeneous than 

 those around British shores. 



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 



