258 INTERMEDIATES IN REDUCTION OF CO2 CHAP. 10 



photochemical oxidation of formaldehyde in vitro; cf. Spoehr 1913, 1916) 

 is a difficult problem, because as long as air is present the formation of 

 sugars or starch from formaldehyde in light can be explained by a pre- 

 liminary oxidation (or photoxidation) to carbon dioxide, followed by 

 normal photosynthesis, as was pointed out by Willstatter and Stoll 

 (1918). Thus, to be entirely convincing, formaldehyde feeding experi- 

 ments should be carried out in darkness, or in the absence of air. Of the 

 earlier investigators, Bokorny, Bouilhac, and Grafe found that form- 

 aldehyde assimilation occurs only in light, while Baker's experiments 

 indicated that it can take place in the dark as w^ell. 



More recently, a number of investigators obtained results apparently 

 confirming Baker's conclusions. Jacoby (1920) found that leaves of 

 Tropaeolum majus, kept in darkness for 24 hours in a stream of form- 

 aldehyde vapor, contained a 20-30% larger proportion of dry matter than 

 the control leaves (e. g., 13.5% dry matter in "formaldehyde leaves," and 

 11.2% in control leaves). However, the absolute quantity of dry matter 

 (as compared with that of fresh leaves) was not increased. In a second 

 paper (1922), Jacoby found that elimination of oxygen does not affect 

 the results. 



In a series of papers on "Aldehydes in Plants," Sabalitschka (1922, 

 1924, 1928), Sabalitschka and Riesenberg (19241-2.3), and Sabalitschka 

 and Weidhng (1926^' 2) obtained results similar to those of Jacoby. 

 They first worked with water plants (Elodea canadensis) in formaldehyde 

 solutions; and observed poisoning only with concentrations above 

 0.02%, i. e., considerably above the limit found by Bokorny (0.005%). 

 Working below 0.02%, Sabalitschka (1922) found that formaldehyde 

 was oxidized in light to formic acid, and the latter used for photosynthesis. 

 In darkness, however, formaldehyde was converted directly into sugars 

 or high polymers. Sabalitschka and Riesenberg (1924^) made experi- 

 ments with whole plants of Phaseolus multifiorum in a formaldehyde 

 atmosphere, and found that the formaldehyde-fed plants contained three 

 or four times more sugar and starch then starved control plants. The 

 total dry weight was sometimes (but not always) larger than before the 

 experiment. 



In his next paper, Sabalitschka (1924) investigated the stimulating 

 effects of formaldehyde on the germination of seeds, fermentation of 

 glucose by yeast, etc., and concluded that the concentrations of form- 

 aldehyde which gave positive results in feeding experiments (0.001%) 

 were not likely to affect the activity of the enzymatic system responsible 

 for the polymerization process. Sabalitschka and Weidling (1926^) 

 returned to experiments on Elodea in formaldehyde solutions, and found 

 that the highest concentration of starch is obtained by feeding a 0.024% 

 formaldehyde solution (21.9% of dry weight in formaldehyde leaves, as 



