IN FRESH- WATER ALG^E 107 



will be given. It may be noted that in the course of growth the 

 experiment was demonstrated to many scientific friends, and 

 exhibits made at meetings of societies, such as the Biochemical 

 and Royal Microscopical Societies, and it was admitted 

 that the differences in growth existed; this is confirmed by 

 the nitrogen determinations now given at the conclusion of the 

 experiment. 



July 1, 1918. No. 1, no growth; No. 2, slight green growth; 

 Nos. 3 and 4, no growth; No. 5, growth in clumps; No. 6, one spot 

 of growth only; No. 7, strong dark green growth all over bottom 

 and sides, best of series; No. 8, slight growth; No. 9, slight growth, 

 better than No. 8; No. 10, no growth; No. 11, fair growth; No. 12, 

 no growth. 



July 20, 1918. No. 1, no growth; No. 2, fair growth, quite 

 obvious difference between Nos. 1 and 2 ; Nos. 3 and 4 (in darkness), 

 no growths; No. 5, good growth in thick discrete clumps; No. 6, only 

 one colony, commencing to degenerate; No. 7, the best of the series. 

 Abundant dark green growth and many gas bubbles; No. 8, fair 

 growth, but distinctly less than in Nos. 7, 9, 11 ; Nos. 9 and 11, both 

 show three or four times as much green growth as No. 8; No. 10, 

 no growth; No. 12, very slight growth. 



At the end, just before Kjeldahling, a microscopical examination 

 was made of Nos. 5, 7, 9, 11. All these showed almost pure growths 

 of small round single green cells (chlorella) ; there were no mycelia 

 or spores or other types of non-green cells. 



Commentary. Several distinct facts are shown by this experi- 

 ment, and taking the final amount of nitrogen as quantitative guide, 

 these will now be pointed out. It is interesting in the first place 

 to notice the increase in nitrogen which could only come from the 

 atmosphere in those cases where no source of nitrogen was added 

 from without, but other essential conditions of growth were more 

 or less perfectly satisfied. It is next of importance to note the 

 effects of limiting each essential factor in turn namely, carbon 

 dioxide, easily available nitrogen (nitrites), alkaline phosphate and 

 to note the great swing in photo- synthesis in No. 7, where all are 

 adequately satisfied. Lastly, the important proof is clearly furnished, 

 we believe for the first time, that carbon dioxide can be completely 

 cut off if its place be supplied by simple organic substances, such as 

 formaldehyde and methylic alcohol, which have hitherto been 

 regarded as the first products of photo- synthesis in the green cell,. 



