56 Prof. B. Moore, Messrs. E. Whitley, and T. A. Webster. 



Nesslerising at the termination of the experiment, and the amount in each 

 case was found to be 1*3 mgrm. per litre. Also, in each case, analysis for 

 nitrite and nitrate gave in both cases 1 in 10 million to 1 in 15 million 

 expressed as nitrogen. It follows that the nitrogen converted by the growth 

 in light of the algee could not be obtained from combined nitrogen as 

 ammonia, nitrite or nitrate. The only other available source is dissolved 

 nitrogen in the sea water derived from the air.* 



A glance at the fifth column of the Table given below shows that the four 

 jars, closed air-tight but kept in sunshine, fixed nitrogen almost as rapidly as 

 the open jars in sunshine. This furnishes proof that the source of the 

 nitrogen fixed is not the nitrogen peroxide, or so-called ozone, of the air, but 

 the elemental nitrogen. This does not, of course, exclude nitrogen peroxide 

 as a nutrient and a stimulant ; experiments in the preceding communication 

 by Moore and Webster on fresh water algae have shown that dilute nitrogen 

 peroxide can so functionate. But both series of experiments agree in proving 

 that, given an ample supply of carbon — either as carbon dioxide or as 

 bicarbonate, and the presence of light-energy, then elemental nitrogen from 

 the air in solution in the nutrient medium can be fixed and built up into 

 organic compounds. At the conclusion of the series of experiments, the four 

 samples of weed in each set of four bottles were separated from the sea 

 water, united, pressed between filter papers, and the moist weight taken. 

 As at the outset, 0'5 grm. was weighed out into each jar ; the initial weight 

 in each set was 2 grm. 



After weighing, each set of weed was placed in a wide-mouthed glass- 

 stoppered bottle, and preserved in a quantity of about 80 c.c. of absolute 

 alcohol. 



When the analyses were started, the preliminary step in each case was to 

 evaporate off the alcohol in a weighed capsule, add the preserved weed, and 

 dry to constant weight ; these dried weights are recorded in Column 4 of the 

 Table. Then each dried weight was analysed for nitrogen by the usual 

 Kjeldahl method, and the results are given in Column 5. 



Commentary on Table I. — The figures given in Column 2 show the alkalinity 

 developed by the photo- synthesis. Notice how much greater it is in full light 

 than in diffuse light, and that in complete darkness it becomes negative 

 because the carbon dioxide discharged in oxidative processes in darkness 

 renders the sea water acid to phenolpthalein. The normal sea water at this 

 period possessed an alkalinity to this indicator represented by about 2"5 c.c. 

 per 100 c.c. of sea water. The alkalinity tends to rise higher in the " shut " 

 jars in sunshine, because in the " open " jars in sunshine the atmospheric 



* See note at end of paper. 



