STUDIES OF PHOTO-SYNTHESIS IN MARINE ALGM 110 



Marine Biological Station, Port Erin. This weed is well suited to 

 the purpose because it is easily divided and can be accurately 

 weighed out in definite amount. A quantity of the enteromorpha 

 was gathered and relieved of excess of sea water by pressing gently 

 between folds of filter-paper. It was then weighed out into 0-5 grm. 

 quantities, and one of these quantities was placed in 200 c.c. of 

 fresh sea water in each Kilner jar. Nothing save the weed and 

 water was added to any jar. The first dozen jars were started on 

 the morning of March 28, and the second set on the afternoon of 

 the same day; they were pickled together in absolute alcohol as 

 preservative on the morning of April 5, and also the waters in 

 which they had grown were taken away for analysis, with the results 

 given below. 



The two sets were treated identically as to exposures, and the 

 first set may be taken as an example for both : 



Nos. 1 and 2. Kept with lids tightly screwed on in such day- 

 light and sunlight as were available outdoors. 



Nos. 3 and 4. Ditto, but instead of tightly screwed-on lids, 

 these were covered above only with a double layer of muslin, so that 

 there was free access of atmosphere. 



Nos. 5 and 6. Exposed to diffuse light only indoors on shelf in 

 laboratory, with lids tightly screwed on. 



Nos. 1 and 8. The same as to light, but open, with muslin covers 

 only. 



Nos. 9 and 10. Kept in complete darkness in cupboard with lids 

 tightly screwed on. 



Nos. 11 and 12. Also kept in darkness in cupboard with muslin 

 cavers only. 



At intervals, as noted in the subjoined table, a quantity of 

 100 c.c. of sea water was taken from one jar of each type of exposure, 

 4 drops of 0-5 per cent, of phenolphthalein were added, and the 

 water was titrated to neutrality with the results shown. Then 

 100 c.c. of fresh sea water were added to restore the former volume, 

 and the jar restored to statu quo as to exposure. The samples of 

 weed in each set of four jars with identical exposures did not during 

 the experiment ever receive more than 1000 c.c. of sea water in all. 

 Samples of fresh sea water, and of that from the jars open in sunlight, 

 were analysed for amino-nitrogen by Kjeldahl destruction and 

 Nesslerising at the termination of the experiment, and the amount 

 in each case was found to be 1-3 mgrms. per litre. Also, in each case, 



