ASSIMILATION OF CARBON 3 1 



to light and carbon dioxide; if the plants had previously been deprived of both 

 light and this gas they gave, as did also fungi, no reaction for aldehyde/ 



Formaldehyde can be utilized by green plants in the formation of carbohy- 

 drates, but none is absorbed in darkness. 1 



Walther Lob's 2 interesting researches have furnished experimental evidence 

 in favor of Baeyer's hypothesis. He used a silent electric discharge as source 

 of energy, instead of sunlight, and established the following principal reactions 

 between carbon dioxide and water, etc. 



1. 2 C0 2 = 2 CO + 2 



2. CO + H 2 = C0 2 + H 2 



3. H 2 + CO = H 2 CO 



4. CO + H 2 = HCOOH 



5. 3 2 = 2O3 



6. 2 H 2 + 2O3 = 2 H 2 2 + 2 



The formation of formaldehyde was limited by the last three (^secondary) 

 reactions; hydrogen combined more easily with oxygen, to form hydrogen 

 peroxide, than with carbon monoxide. To obtain formaldehyde in greater 

 quantity Lob added a reducing agent (salicylic aldehyde, pyrogallol or 

 chlorophyll). Glycolic aldehyde (which represents the simplest sugar), as well 

 as formic acid and formaldehyde, arises from the action of the silent discharge 

 upon carbon monoxide, water, and hydrogen; 2(H 2 + CO) = CH 2 OH — 

 CHO (glycolic aldehyde). By the concentration of its solution in vacuo this 

 substance is readily transformed into a tetrose or hexose. 3 



Stoklasa and Zdobnicky 4 found that formaldehyde was formed by the action 

 of ultra-violet light upon water vapor and carbon dioxide in the presence of 

 potassium hydroxide, but no carbohydrates were thus produced. Sugar was 

 formed, however, under these same conditions, when hydrogen was present in 

 the nascent state.' 



1 Grafe, Viktor, Untersuchungen uber das Verhalten gruner Pflanzen zu gasformigen Formaldehyd. II 

 Ber. Deutsch. Bot. Ges. 29: 19-26. 191 1. Idem, Die biochemische Seite der Kohlensaure-Assimila- 

 tion durch die griine pflanze. Biochem. Zeitsch. 32: 114-129. 1911. [Baker, Sarah M., Quantitative 

 experiments on the effect of formaldehyde upon living plants. Ann. bot. 27:411-442. 1913.] 



2 Lob , Walther, Zur Kenntnis der Assimilation der Kohlensaure. Landw. Jahrb. 35 : 541-578. 1906. 

 Bach, A., Sur 1'evolution biochimique du carbone. Arch. sci. phys. et nat. 5:401-415, 520-535. 1898. 



This deals with the theory of photosynthesis. 



4 Stoklasa, J., and Zdobnicky, W., Photochemische Synthese der Kohlenhydrate aus Kohlensaurean- 

 hydrid und Wasserstoff in Abwesenheit von Chlorophyll. Biochem. Zeitsch. 30 : 433-456. 191 1. 



8 On reactions for identifying formaldehyde in plant parts, see Haas and Hill, 192 1. [See 

 note 3, p. 6.]— Ed. 



1 Further, on the artificial formation of formaldehyde, etc., from carbon dioxide and water, 

 see: Berthelot, D., and Gaudichon, H., Synthese photochimique des hydrates de carbone aux 

 depens des elements de l'anhydride carbonique et de la vapeur de l'eau, en l'absence de chloro- 

 phylle; synthese photochimique des composes quartenaires. Compt. rend. Paris 150: 1690- 

 1693. 1910. For a review of this general subject, see: Spoehr, H. A., Theories of photosyn- 

 thesis. Plant world 19: 1-16. 1916. It should be remembered that the reactions that take 

 place in leaves may not be the same as those studied in vitro. Very little experimental work 

 has been done on the photochemical changes to which chlorophyll itself is subject. — Ed. 



