154 THE CARBOHYDRATES 



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 Trebouxf and Bouilhac 

 have stated that Elodea, 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 \ 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 1*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, I7i ^ '. " ^er. deut. chem. Gesells.," 1891, 

 24, 103. 



fTreboux: " Flora," 1903, 92, 49. 



tGrafe: " Ber. deut. bot. Gesells.," igii, 29, 19. 



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



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



