10 H. A. SPOEHR 



of leaves, yield formaldehyde on exposure to the light. Formic 

 acid, however, does not yield formaldehyde. In fact, it is not 

 improbable that there are a large number of substances in the 

 plant which produce formaldehyde under various conditions. 

 Hence it is quite evident that the finding of formaldehyde in 

 illuminated leaves is of little value in the proof of the Baeyer 

 hypothesis. 



As to the experiments in which formaldehyde was given plants 

 as the only source of carbon, the results are also somewhat con- 

 tradictory. Formaldehyde has always proved to produce de- 

 cidedly toxic effects even in concentrations of 1 : 20,000 ; although 

 Treboux^^ found that Elodea could well stand a solution of 0.001%, 

 but formed no starch. Loew and Bokorny^* found that the so- 

 dium bisulphite compound of formaldehyde is not only very 

 much less toxic, but that from solutions of this compound, in the 

 presence of mineral nutrients, starch is formed by several algae. 

 It is very important to remember, however, that these solutions 

 are always slightly alkaline, which would have the effect of con- 

 densing the formaldehyde to sugar, and thus that it is from this 

 latter substance that the plant is producing starch. Recently 

 Bokorny reported that Spirogyra formed starch from a 0.001% 

 solution of formaldehyde, and that this action was greatly accel- 

 erated by the action of light. The necessity of light for the uti- 

 lization of formaldehyde by the plant has been clearly shown 

 in the experiments of Grafe.^^ He showed that only those por- 

 tions of the plant bearing chlorophyll are not injuriously affected 

 by the formaldehyde in the hght. In darkness formaldehyde is 

 toxic to all plant parts. However, in these experiments there was 

 no formation of starch in the leaves of the plants used {Phaseohis 

 vulgaris), due probably to the inhibiting action of formaldehyde 

 on the amylase. 



2' Treboux, O., Einige stoffliche Einfliisse auf die Kohlensaure-assimilation bei 

 submersen Pflanzen. Flora 92 : 49-76, 1903. 



2* Bokorny, T., Ueber Starkebildung aus Formaldehyd. Ber. deut. Bot. Ges. 

 9: 103-6, 1891. Archiv. fur Ges. Physiol. 125: 467-90, 1908. Ibid 128: 56.5, 1909. 

 Biochem. Zeitschr. 36:83-97, 1911. 



^^ Grafe, V., Untersuchungen liber das Verhalten griiner pflanzen zu gas- 

 formigen Formaldehyd. Ber. deut. Bot. Ges. 27: 19, 1909; 29: 431, 1911. 



