8o Ingvar Jorgensen and Walter Stiles. 
incomplete, it is impossible to draw conclusions from experiments 
in which the conditions are clearly so different. 
The experiments in relation to Baeyer’s hypothesis fall into 
three groups :— 
1. Experiments on the formation of formaldehyde in (a) 
systems containing carhon-dioxide and water, ( b ) systems con¬ 
taining carbon-dioxide, water and chlorophyll, ( c) leaves. 
2. Experiments on the formation of sugars from form¬ 
aldehyde. 
3. Feeding experiments with formaldehyde. 
1. (a) The production of formaldehyde from carbon dioxide and 
water in the absence of chlorophyll certainly seems possible under 
certain conditions. For instance, Fenton (1907) and D. Berthelot 
and Gaudechon (1910) have each succeeded in reducing carbon- 
dioxide to formaldehyde under appropriate conditions, but there is 
no evidence that these conditions are in the least comparable to those 
in the plant. References to further work in this connection will 
be found in the paper by Spoehr already cited, in which this side of 
the question is critically dealt with. 
( b) Experiments dealing with the photochemical production 
of formaldehyde from systems containing carbon dioxide, water 
and chlorophyll have all been made with crude chlorophyll, and in 
most cases oxygen has not been removed from the system. In 
order to repeat these experiments critically we ourselves extracted 
some pure chlorophyll ( a + b). The results obtained in the experi¬ 
ments made with this pure chlorophyll are recorded in a paper by 
Jorgensen and Kidd (1916). It was found that the production of 
formaldehyde was always due to the oxidation of chlorophyll. In 
systems containing only carbon dioxide, water and chlorophyll no 
formaldehyde is produced. 
(c) Pollacci (1899—1907), Grafe (1906), Kimpflin (1907) and 
R. J. H. Gibson (1908) contend that formaldehyde can be identified 
in leaves after illumination, while Curtius and Franzen (1912) 
contend that other aldehydes are produced, e.g., <x (3 hexylene 
aldehyde, but in view of the critical experiments of Fincke (1913) 
and Spoehr (1913) it is clear that under various conditions a large 
number of substances in the plant will produce aldehydes. 
Thus experiments of this type do not give support to the formal¬ 
dehyde hypothesis. 
2. In view of the experiments of Butlerow (1861), Fischer 
(1888, 1889) and Loew (1889), and above all Nef (1910, 1913) it 
