439 
the Effect of Formaldehyde on Living Plants . 
series, Collie and others 1 have been able to produce representatives of 
almost all the groupings present in plants and animals (including many 
nitrogen compounds), by means of such reactions as hydrolysis, in ammo- 
niacal or faintly alkaline solutions, at ordinary temperatures. This sugges- 
tion practically combines the formaldehyde hypothesis with the ingenious 
and suggestive multiple-photosynthesis hypothesis , 2 and it has moreover 
much chemical evidence to support it. The formation of the exceedingly 
unstable CH 2 =CO molecule from formaldehyde would probably be endo- 
thermic, and so require light energy. 
The action of certain of these polyketides on plants is at present under 
investigation, but it would be useless to go into a further discussion of this 
theory until more experimental data are available. 
Summary. 
Experiments have been described in which seeds were grown in an 
atmosphere containing known quantities of formaldehyde vapour in light 
and darkness. A comparison of the change in dry weight with that of 
control cultures with and without carbon dioxide revealed the fact that 
formaldehyde could be used for the synthesis of food materials to some 
extent in the light. The gain in dry weight produced was about half the 
loss due to respiration, and an increase in the percentage of formaldehyde 
in the air did not produce a corresponding increase in dry weight after 
a certain concentration. An excess of formaldehyde was toxic. 
In the dark formaldehyde was not assimilated, but seemed to stimulate 
respiration. Its poisonous effect was more marked than in light. 
Experiments with acetic aldehyde showed that formaldehyde was not 
assimilated in light merely by virtue of the aldehyde group ; for acetic 
aldehyde could not be taken up by the plants. 
The results were capable of two interpretations : either formaldehyde 
is a step in respiration, and converted by the plant into carbon dioxide 
before it can be assimilated ; or it is the first step in photosynthesis, and its 
further elaboration by the tissues requires light energy. 
In order to decide between these two possibilities, quantitative experi- 
ments were made in which the change in dry weight of the cultures could 
be directly compared with the carbon dioxide evolved during respiration. 
It was found that this ratio agreed closely with that calculated for the 
complete oxidation of a carbohydrate. When formaldehyde was passed 
over the cultures in the dark, there was no change in the quantitative 
relations between the loss in dry weight of the cultures and the carbon 
dioxide of respiration. Hence formaldehyde was not converted into carbon 
dioxide by the plants, nor used as a source of food materials in the dark. 
1 Cf. chapter on Polyketides in Stewart : Recent Advances in Organic Chemistry, London, 
1908, p. 44. 
2 Brunner and Chouard : Ber. d. Deut. Chem. Ges., 1886, xix, p. 595. 
