FORMALDEHYDE IN GREEN LEAVES 157 



under certain conditions, formaldehyde may be made use of 

 by the plant. Thus Bokorny* showed that Spirogyra can 

 make starch when supplied with a compound of formaldehyde 

 and sodium hydrogen sulphite ; also Treboux f and Bouilhac 

 have stated that Ebdea, Sinapis, and certain Algae can form 

 starch in the dark when supplied with dilute (-0005 per cent) 

 solutions of formaldehyde. 



In this connexion Grafe's J results are important, for he 

 found that if green seedlings be grown in the light in an 

 atmosphere containing no carbon dioxide but formaldehyde 

 vapour (not more than i'3 per cent), they show a greater 

 increase of growth and in dry weight as compared with 

 controls grown under the same conditions, but without the 

 formaldehyde. 



The next question which naturally arises is whether formal- 

 dehyde occurs in assimilating leaves, and whether it is possible 

 to reproduce in vitro, with the aid of a suitable sensitizer, the 

 preliminary action which is supposed to take place in the 

 plant, viz., the formation of formaldehyde from water and 

 carbon dioxide. 



Reinke § in 1883 was one of the first instigators to discover 

 formaldehyde in green leaves, and Curtius and Reinke II some 

 years later stated that aldehydes occur in chlorophyll-containing 

 cells, provided they be exposed to light ; these substances, 

 however, do not occur in Fungi. Amongst the first to attempt 

 to reproduce in a test tube the supposed initial photosynthetic 

 stages was Bach, who states that formaldehyde is produced 

 from carbon dioxide in the presence of water by the action of 

 sunlight, provided that a suitable optical sensitizer, such as 

 uranium acetate or dimethyl aniline, be employed. In other 

 words, the formation of formaldehyde in the leaf is not a vital 

 process. He also found that this same substance is produced 

 from carbonic acid in the presence of hydrogen palladium, 

 which acts as the reducing agent. 



* Bokorny: " Biol. Centrbl.," 1897, 17, i ; " Ber. deut. chem. Gesells.," 1S91, 

 103. 



t Treboux : " Flora," 1903, 92, 49. 

 JGrafe: "Ber. deut. bot. Gesells.," 191 1, 29, 19. 

 § Reinke: "Ber. deut. bot. Gesells.," 1883, i, 406. 

 II Curtius and Reinke: " Ber. deut. chem. Gesells.," 1897, 30, 201. 



