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 réle 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 
