Studies of Photo -synthesis in Marine Algce. 



57 



carbou dioxide can enter through the muslin and partially re-neutralise the 

 normal carbonates of magnesium and calcium formed. 



Table I. — Fixation of Nitrogen by Marine Algai. Experiment of 

 March 28-April 5, 1919 (seven days' interval). 



1. 



Nature of exposure. 



2. 



Titration in 

 c.c.'s of N/lOO 

 acid in 100 c c. 

 of sea water 

 required to 

 neutralise to 

 phenolphthalein. 



3. 



Wet weight at 

 end. Initial 

 weight in eacli 

 case, 2 grm. 

 in 800 c.c. 

 'sea water. 



4. 



Dry 

 weight at 



end in 

 grammes. 



5. 



Total 

 nitrogen by 

 Kjeldahl. 

 In milli- 

 grams. 





Sunlight, in xAuf jars, 





April 2. 



April 5. 









1. 



out. 



13 -3 



9-7 



2 '57 



0-476 



11 -3 





doors 















2. 



Sunlight, in open jars, 



out- 



6-7 



9-7 



2-38 



-457 



12-4 





doors 















3. 



Diffuse light, no direct 



sun. 



0-4 



3 -4 



1 -71 



0-284 



8-7 





on shelf indoors. Shut iar 













4. 



Same exposure as No. 3 



but 



-0 



+ 1-7 



1 -47 



0-285 



8-0 





jars open 















5. 



Darkness, in cupboard. 



Shut 



-1-7 



-1 -4 



1 •4.5 



0-259 



9-4 





jars 















6. 



Same as 5, but jar open 





-1-2 



-0-3 



1 -50 



0-275 



9-5 



It is of some interest to make a rough calculation of the quantities of fixed 

 carbohydrate, protein or fat that these amounts of fixed carbon dioxide, as 

 estimated from the titrated increases of alkalinity, would account for during 

 the period of experiment. Taking the mean of the two amounts of 

 alkalinity upon the two days observed, viz., 13-3 and 9-7, one obtains 11-5. 

 Deducting 2-5 c.c. for the level of normal sea water at this period of the year 

 the result is 9-0 c.c. of centi-normal alkali resulting from photo-synthesis per 

 100 c.c. This change occurred in 800 c.c. in each set for a period of seven 

 days. This works out at 500 c.c. of centi-normal alkali during the period. 

 Now 1000 c.c. of normal alkali corresponds to 12 grms. of carbon fixed, and 

 on this basis the carbon fixed is 60 mgrm. This would correspond, on the 

 basis of 45 per cent, of carbon in carbohydrates, 60 per cent, in proteins and 

 75 per cent, in fats, to a fixation of 130 mgrm. of carbohydrate, 100 mgrm. of 

 protein or 80 mgrm. of fats. 



Turning now to the increased moist weight during the experiment from 

 2-00 grm. to 2-57 grm. and taking the dry weight at the end of 0-476 grm., the 

 increase in dried weight works out at 106 mgrm. 



There is thus a close correspondence between the increase in weight and 

 that which would be expected, viz. : increase lq dried weight found 106 mgrm. ; 



