ASSIMILATION OF FORMALDEHYDE 41 



These substances, as is well known, are poisonous, so that, 

 if formed, they must be polymerized before they have time to 

 injure the protoplasm, and experiments have shown that, 

 under certain conditions, formaldehyde may be made use of 

 by the plant. Thus Bokorny * showed that Spirogyra in the 

 absence of carbon dioxide can make starch when supplied with 

 a compound of formaldehyde and sodium hydrogen sulphite ; 

 also Treboux f 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. 



Grafe \ found that green seedlings grown in the light, in an 

 atmosphere free from carbon dioxide and containing not more 

 than I -3 per cent of formaldehyde vapour showed a greater 

 increase in growth and in dry weight as compared with the 

 controls. These results were corroborated by Baker who 

 concluded from most carefully controlled experiments that 

 formaldehyde could be assimilated to a certain extent in the 

 light, but not in the dark, in an atmosphere void of carbon 

 dioxide. 



With regard to the presence of formaldehyde in green 

 leaves there is much positive evidence || and mention has 

 already been made of the formation of formaldehyde and of 

 formic acid from carbon dioxide and water under the influence 

 of different forms of energy. 



Willstatter and Stoll 1F argue that the " assimilatory ratio," 

 CO 2 /O 2 , should provide evidence regarding the possible inter- 

 mediate products; they point out that oxalic, formic and 

 glyoxylic acids and formaldehyde are possible intermediate 

 products between the carbon dioxide and carbohydrate. The 

 assimilatory ratios of these substances are respectively, 4, 2, 

 I -3 3 and I. Under the conditions of their experiments, they 

 found the assimilatory ratio to be I and it remained constant, 

 even in succulents, under varying conditions in the amounts of 

 carbon dioxide and oxygen and with the temperature ranging 



* Bokorny: " Biol. Zentrbl.," 1897, 17, i, 1916, 36, 385 ; " Ber. deut. chem. 

 Gesells.," 1891, 24, 103. 



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



% Grafe: "Ber. deut. hot. Gesells.," 1911, 29, 19. 



Baker : "Ann. Bot.," 1913^27, 411. 



|| See Vol. I., Section on Aldehydes. 



IF Willstatter and Stoll: " Ber. deut. chem. Gesells.," 1917, 50, 1777. 



