CHAPTER VIII 

 STUDIES OF PHOTO-SYNTHESIS IN MARINE ALGM 



1. FIXATION OF CARBON AND NITROGEN FROM INORGANIC SOURCES 

 IN SEA WATER. 2. INCREASE OF ALKALINITY OF SEA WATER 

 AS A MEASURE OF PHOTO-SYNTHESIS. 



THE results of a series of observations upon marine algae confirm and 

 amplify those obtained with fresh- water algae, which, as recorded 

 in the preceding chapter, show a convincing uptake of nitrogen from 

 the air, but on account of the change of the medium of growth from 

 fresh to sea water there are several important modifications in the 

 medium itself as well as in the growing algae, which appear to 

 possess considerable importance in the annual life of the sea, and 

 in the inductance at certain definite periods of the year of increased 

 processes of cell division and reproduction of species, and possibly 

 may guide the development of variations in species, and the process 

 of evolution. The details of seasonal variation in growth are 

 furnishing to us at present most interesting results, but here will 

 be recorded only work now completed dealing with light action 

 apart from seasonal variation. 



There is in the case of marine plants none of that uncertainty 

 which obtains in the case of the higher terrestrial plants as to how 

 much of the nitrogen being built into organic compounds comes from 

 the roots. Even in the case of such massive plants as Laminaria 

 and Fucus it is obvious that the roots are merely modes of attach- 

 ment to the rocks, and that the whole plant is built up from the sea 

 water. It is an impossibility that nitrogen could be extracted from 

 the hard stones to which the plants are anchored, and in the case of 

 the floating diatoms, and other minute green cells, which form the 

 phyto-plankton, floating free in the sea, it is clear that the whole 

 organism is formed from the sea water. Hence the entire plant life 

 of the sea is produced by the action of sunlight upon the water of the 

 sea and its dissolved constituents. In so far as sources of ready- 

 formed and easily absorbable nitrogenous compounds are concerned, 

 the sea water is remarkably poor, and the volumes of sea water 



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