STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 6 



that physiology is a great deal more than applied physics and chem- 

 istry, although we must rely upon these discipUnes in order to form 

 conceptions of the various vital phenomena as operations of known 

 causes. With complete disregard of biological facts, chemists have 

 continued to evolve theories of the chemistry of photosynthesis 

 and to supplement and modify existing theories. The fundamental 

 fallacy in these speculations has been that photosynthesis has been 

 regarded — to quote a recent technical article — as ''simply a manu- 

 facture that provides material used in the process of living, "^ that 

 because a process can be suspended for hours and months it is not a 

 process or function of the Uving. The many attempts which have 

 been made to reproduce the photosynthetic process apart from the 

 Uving cell have not been successful.^ This also appHes to the experi- 

 ments in which various chlorophyll preparations have been used, 

 as well as to those in which ultra-violet Ught was employed as a 

 source of radiant energy, although the latter conditions have no 

 direct bearing on photosynthesis, because normally the plant makes 

 use of only the radiations in the visible spectrum. 



That the photosynthetic process is intimately associated with 

 the protoplasmic activity of the hving cell was recognized a long time 

 ago. Boussingault,^ in his studies of the effect of gases such as 

 hydrogen, nitrogen, and methane on photosynthesis, came to this 

 conclusion. The same conclusion was reached and somewhat 

 elaborated by Pringsheim." Interesting and valuable as these 

 older investigations are, as well as the later ones of Ewart,^ Httle 

 precise information can be gained from them, because the methods 

 of experimentation and observation are naturally not in accord with 

 present standards of accuracy. 



It has become evident that further insight into the complex 

 phenomenon of photosynthesis is to be gained only by means of 

 intensive study of the process under very carefully controlled external 

 conditions and the ehmination of secondary factors. Unfortunately, 

 however, in the study of photosynthesis, internal conditions, such 

 as available nutritional material, have been totally neglected and 

 httle or no regard has been paid to the previous history of the plant. 

 It is highly probable that this neglect in many instances accounts 



1 Scientific American Supplement, No. 2257, 223 (1918). 



* WiLLSTAETTER, R., and A. Stoll. Untersuchungen ueber die Assimilation der Kohlensaeure. 



1918, 391-415. 

 Spoehh, H. a. The theories of photosynthesis in the light of some new facts. Plant World, 

 19, 1-16 (1916). 

 ' BoussiNGAULT, J. B. ^Itude sur les fonctions des feuilles. Compt. rend., 60, 608; 1865, Agro- 

 nomie, 4, 359-397 (1868). 



* Pbingsheim, N. Ueber die Abhaenigkeit der Assimilation Gruener Zellen von ihrer Sauer- 



stoffathmung, und den Ort, wo der im Assimilationsacte der Pflanzenzelle gebildeter Sauer- 

 stoff entsteht. Sitzber. Preus. Akad. Wiss., 763-777 (1887). 

 ' EwART, A. J. On assimilatory inhibition in chlorophyllous plants. Jour. Linnean Soc, 31, 

 364-^61 (1896); 556 (1897). 



