412 
Baker.— Quantitative Experiments on 
and Berthelot 1 and their collaborators on the effect of ultra-violet light on 
carbon dioxide and water seems in some ways closely analagous to natural 
photochemical reactions. Besides this, Usher and Priestley 2 have brought 
forward evidence of the production of formaldehyde and hydrogen peroxide 
from carbon dioxide and water by means of chlorophyll in sunlight. 
Direct evidence as to the presence of formaldehyde in plant tissues 3 
or its effect on living plants has, however, been meagre. The well-known 
toxicity of formaldehyde precluded its application in aqueous solutions, 
except at very great dilutions . 4 
Th. Bokorny 5 was the first to try the effect of formaldehyde vapour on 
plants. He found that cress seeds could be grown, in an air-space con- 
taining formaldehyde vapour, for thirty days, while those without formalde- 
hyde came to grief much sooner. But Viktor Grafe 6 considerably elaborated 
and extended Bokorny’s methods, and tried the effect of formaldehyde and 
other vapours on seedlings of Phaseolus vulgaris . He found that in light 
formaldehyde vapour could be tolerated up to a large percentage in the air, 
but its toxic effect at once became pronounced in darkness, or on colourless 
parts of the plant. He also found a noticeable increase in the size of the 
formaldehyde cultures in light (as compared with controls free from carbon 
dioxide), but no sign of increase in the dark. He tried several other com- 
pounds : acetic, salicylic, and benzoic aldehydes, and also acetic and benzoic 
acids, but found no increase in these cases. Although these results indicate 
the possibilities of using formaldehyde in vapour form as a source of carbon 
for higher plants, they are all purely qualitative, and it seemed very 
desirable to have a definite quantitative determination of its effect on living 
plants in order to test the value of the chemical theories, involving the 
production of formaldehyde, in the course of photosynthesis. 
General Aim of the Experiments. 
The quantitative treatment of living material is a process involving 
many difficulties. In the experiments to be described the idea has been to 
subject plants to the action of formaldehyde vapour, and to estimate the 
gross effect of the reagent by weighing the cultures dry before and after 
treatment. Dry seeds have been used as the starting-point for every 
experiment, and, in order to grow these in an atmosphere of known 
composition and under as nearly as possible natural conditions, a somewhat 
complicated apparatus was used, which it is necessary to describe in detail 
before proceeding to the actual experiments. 
1 Berthelot and Gaudechon : Compt. Rend., 1910, cli. 395—7. 
2 Usher and Priestley : Proc. Roy. Soc., vol. Ixxxiv, B, p. 101. 
3 Bokorny: Chem. Zeit., 1909, xxxiii. 1141-2 and 1150-1. 
4 Bokorny: Biochem. Zeitschr., 1911, xxxvi. 83-97. 
B Bokorny: Pfliigers Archiv fur Physiologie, Bd. cxxviii, S. 565, 1905. 
e Grafe : Ber. d. Deut. Bot. Ges., xxix, 1911, Heft iv, S. 19. 
