PRODUCTION OF ALDEHYDE IN PRESENCE OF SUNLIGHT 513 
that it makes practically no difference in the result whether CO2 is 
excluded altogether from the bell jar or whether the concentration is 
increased to 10 percent but it was found that the presence of oxygen is 
necessary. The writer therefore came to the conclusion that the 
aldehyde is not produced by the decomposition of CO2 but rather by 
the decomposition of chlorophyll. 
Subsequently a number of criticisms of the work of Usher and 
Priestley have appeared, to which these authors have replied.^ Re- 
cently several authors'^ have stated that the aldehyde produced in 
Usher and Priestley's experiments is the result of oxidative decom- 
position of chlorophyll. Wager and Ewart believe that decomposition 
of chlorophyll, and the resulting formation of aldehyde, is a regular 
step in photosynthesis. There is some evidence in favor of this view,^ 
but at present it cannot be said that there is any convincing proof of 
its correctness. 
Summary 
1. A method is described by which aldehyde is obtained from 
chlorophyll in sunlight; the yield is relatively large and it is free from 
contamination by non-volatile substances. 
2. A similar production of aldehyde is observed when certain 
aniline dyes are substituted for chlorophyll. 
Harvard University, 
Laboratory of Plant Physiology 
6 C/. Usher, F. L., and Priestley, J. H, Proc. Roy. Soc. Lond. B. 84: iii. 1911. 
7 Cf. Wager, H. Proc. Roy. Soc. Lond. B. 87: 386, 596. 1914; Warner, C. H. 
Ibid. 87: 378. 1914; Ewart, A. J. Ibid. 89: i. 1915; Jorgensen, I., and Kidd, F. 
Ibid. 89: 342. 1916. For the decomposition of other substances in light, with 
production of aldehyde, see Neuberg, C. Biochem. Zeit. 13: 305. 1908; Spoehr, 
H. A. Biochem. Zeit. 57: 95. 1913. 
^ That chlorophyll or some compound of it may decompose during photosynthesis 
is indicated by a recent study of the dynamics of the process. See Osterhout, 
W. J. v., and Haas, A. R. C. Proc. Nat. Acad. Sci. 4: 85. 1918. Journal of Gen- 
eral Physiology 19 18. 
