290 PHOTOSYNTHESIS 



questionably other substances are present in these preparations which also 

 give an aldehyde reaction. 



Curtius and Franzen proposed the detection of formaldehyde by con- 

 version into formic acid which can be easily distinguished. Fincke dem- 

 onstrated that this method was unreliable and that a macerated mass 

 of fresh leaves fixes or destroys formaldehyde which has been added to 

 the mass so that the aldehyde cannot be distilled oflf. This fixation of 

 formaldehyde by plant material is not confined to portions containing 

 chlorophyll. When formaldehyde is added to a macerated mass of plant 

 material and the juice is expressed, the fixation is less than when the 

 material is subjected to steam distillation. Under any circumstances this 

 would indicate that it is extremely difficult to detect small quantities of 

 formaldehyde in plants. If more drastic means are employed to liberate 

 any formaldehyde which may be present, there is danger of decompos- 

 ing material in the plant tissue which may result in the formation of 

 formaldehyde. 



Kimpflin ^^ has endeavored to demonstrate the presence of formalde- 

 hyde in the immediate neighborhood of the chlorplasts by microchemical 

 means. But these results as well as those of others who have announced 

 the finding of formaldehyde are of very doubtful value in view of the 

 findings of Curtius and Franzen that other aldehydes give the same or 

 very similar reactions. 



Another feature of the question of the presence of formaldehyde in 

 plants is the necessity of deciding whether any formaldehyde which 

 may be there is actually associated with the photosynthetic process. 

 Spoehr "^^ has shown that a number of substances which are components 

 of plants yield formaldehyde when solutions of these substances are ex- 

 posed to the light. Neuberg *^^ has also shown that methyl alcohol and 

 glycocoll do the same, and similar reactions have been observed by others."'' 



Fincke *•' employed the modified Schift" reagent which had been de- 

 scribed by Deniges ^^ and by Grosse-Bohle.''^ He showed that in illumi- 

 nated leaves there was no formaldehyde in concentration greater than 

 1 : 200,000. the safe limit of his method. . 



Recently Sabalitschka and Riesenberg ''^ have also reported that they 



°^ Kimpflin, "Essai sur rassimilation photochlorophylHenne du carbon," Lyon 

 (1908), p. lO'S. Gibson, Ann. Bot., 22, 117 (1908). Gentil, Bull. Ass. Cliim. Sue. 

 Dist., 27, 169 (1914). Kleinstiick, Bcr. chcm. Gcs.. 45, 2902 (1912). Schryver. 

 Proc. Roy. Soc, 82 B, 226 (1910). .A.ngelico and Catalano, Gas. chim. itai, 43, 38 

 (1913) "Priestley and yVrmstead. Nczv Phvtnlofnst. 21, 62 (1922). 



*" Spoebr, Biochcm. Zcit., 57, 95 (1913). 



-^Neuberg, ibid., 13, 305 (1908); 29, 279 (1910). 



""Volmar ConiM- rrnd.. 176, 742 (1923). Benratb. "Photochemie" (1912), p. 

 181 Rosent'balu, .Irji. rharm.. 251, 587 (1914). 



""Fincke, Hiochcm. Zcit.. 52, 214 (1923); 51, 253 (1913). Curtius and Franzen, 

 ^jm. C:/;<'w., 404. 93, 1(.5 (1914). ,., .,on^x 



""Deniges, Compt. rend.. i53, 529 ( 1910) ; .hmr. Pharm. ( lum. (6), 4, 193 (1896). 



*• Grosse-Bohle, Zeit. Nahr.-Genussm.. 14, 88 (1907). 



'"Sabalitschka and Riesenberg, Bioehcm. Zeit., 145, i77 (1924). 



