the Effect of Formaldehyde on Living Plants . 423 
the synthesis of food materials, to a limited extent in light, but not at all 
in darkness. Bouilhac 1 and V. Grafe, 2 working by different methods, have 
previously come to a similar conclusion. 
It may cause surprise that there was no greater increase in dry weight, 
even in the cultures under carbon dioxide. But it must be borne in mind 
that, during the first half of each experiment, before the cotyledons are 
unfolded, no assimilation can take place ; and even in the latter part of the 
experiment a comparatively small green area has to supply materials for 
the respiration of the whole of the root and hypocotyl, besides its own 
requirements, before any increase in dry weight will be shown. It appears 
that in practice no actual increase in dry weight occurs until the first true 
leaves are unfolded ; the assimilation due to the cotyledons being only 
sufficient to compensate for the losses in the first stages of germination. 
As explained above (p. 413), it was not possible to continue an experiment 
long after the culture without carbon dioxide showed symptoms of flagging, 
and so none of the cultures were continued for more than a few days after 
the leaves appeared in the culture under carbon dioxide. 
The Products of Photosynthesis with Formaldehyde. 
Qualitative experiments, on cultures grown simultaneously with Ex- 
periment V, in the light, confirmed Grafe’s statement that no starch is 
formed from formaldehyde either in light or darkness, though the cotyledons 
contained some sugar. This need not necessarily lead to the conclusion 
that the process of photosynthesis is abnormal with formaldehyde, but 
merely that the reaction is not sufficiently vigorous to warrant the storage 
of starch in the corpuscles. Grafe also states that formaldehyde inhibits 
the action of amylase, the enzyme supposed to be the agent concerned in 
the synthesis of starch from sugar. This was not investigated. 
Poisonous Action of Formaldehyde. 
Grafe and Bokorny have already shown that traces of formaldehyde in 
the air do not poison plants in the light. The poisonous effect is, however, 
shown when the concentration of formaldehyde is sufficiently high, even in 
light (see Experiment V, light). The present experiments also show that 
plants grown from seed in the dark, under formaldehyde, show no symptoms 
of poisoning, provided always that the formaldehyde is purified by bubbling 
through caustic potash solution. Grafe’s idea that the presence of chloro- 
phyll acts as a protection against formaldehyde poisoning does not explain 
the case, for symptoms of poisoning were shown immediately after passing 
formaldehyde into a green culture in the dark (Experiment VII). The 
general conclusion to be drawn from the results appears to be that the 
light, or high temperature resulting from it, makes it possible for plants to 
1 Bouilhac et Gustiniani : Comptes Rendus, cxxxvi, 1903, pp. 1 155-7. 
2 Grafe : loc. cit. 
