-] 
Il. Sources for the organic matter in the sea. 
Just as on the dry land, the lifeless organic matter in the sea must in 
the first instance originate from living, carbon dioxide assimilating plants, since 
as known it is only through their agency, that the inorganie materials in nature, 
particularly carbonic acid, are transformed to organic substances. 
On close examination we may divide the organic matter in the sea into 3 
groups according to the place where they are produced. 
1. The organic matter produced in the sea itself. 
2. The organic matter brought down by rivers and streams. 
3. Organic matter carried out from the land into the sea by the agency 
of the wind. 
For a quantitative consideration it is evident that the last source is of no 
importance, in comparison at any rate with the first two; but without committing 
any great error we can also eliminate the second source, so far as the waters are 
concerned with which these investigations chiefly deal. As is known, there is 
only one river of any size which flows out into the Limfjord, namely, the Karup 
River which runs out into Skivefjord. We cannot say how large are the quanti- 
ties of organic materials which this river carries down, but we may certainly 
assume that these materials are deposited in Skivefjord and are of no importance 
for the rest of the Limfjord. 
There only remains for consideration the materials produced in the sea 
itself, in other words, the vegetation of the sea. 
Å review of the plant-formations occurring in water is given by W ar- 
ming: Oecology of plants, 1909, p. 155 et seg. Taking account only of the 
autophytice formations which occur in salt water, we obtain from this review the 
following subdivisions of the vegetation in the sea. 
I. Free-floating or free-swimming plants: 
The plankton formation. 
I. Fixed plants (benthos formation) : 
A. Fixed to stones or rocks: 
The marine algae formation. 
B. Fixed to loose soil: 
Grass-wrack formation. 
Again, the saltwater plankton (haloplankton) is subdivided into 
oceanic and neritic plankton, according as it occurs out in the open sea or at the 
coasts.. The principal forms of the plants occurring in the plankton are various 
diatoms (Chætoceros, Rhizosolenia etc.), Peridineae, Flagellata ete. 
In contrast to the plankton, the benthos formations are bound to the 
coasts. The marine algae grow most luxuriously on rocky coasts, e. g. the 
coasts of Norway, of Great Britain, the Færoes and Iceland. Darwin's descrip- 
tion of the algal forests on the coasts of Patagonia is well-known. In their wealth 
and extent he compares them to the primeval woods of the tropics. The brown 
algae are predominant, in southern seas for example Macrocystis and Sargassum, 
in nothern seas various species of Laminaria, Fucaceae and many more. The 
