PHYSIOLOGICAL SCALE AND LAWS OF PHOTOSYNTHESIS 281 



established by the experimental results described in Chapter 

 XXVI. In nature, however, all the different factors— 

 C0 2 -concentration, intensity of light, temperature and the 

 tonic condition of the plant— are changing simultaneously, 

 each in different ways. The possible different combina- 

 tions of them are too numerous for experimental investiga- 

 tion of all of them. The results obtained in the cases selected 

 prove that the characteristic effect of each factor is un- 

 affected by the effect produced by others : that is to say, if 

 the increase of photosynthetic activity due to three of the 

 principal factors — 



by change from c to C be x times 

 „ /toLbejy „ 

 t to T be z 



then the resulting variation in activity by simultaneous 

 change of all the factors from clt to CLT will be x X y X z, 

 or the product of the partial effects induced by the individual 

 factors. This, in contrast with arithmetical summation, 

 is designated as the Law of Product or of Multiplication. 

 This law of combined effects of different factors in photo- 

 synthesis is expressed by the formula 



A 



CLTP 



is a constant. 



The investigations described in the present work 

 establish the underlying unity of physiological mechanism 

 in the plant. The diverse phenomena of mechanical and 

 electrical response, of growth and of ascent of sap, and of 

 photosynthesis, are but characteristically parallel effects of 

 fundamental protoplasmic reactions associated with storage 

 or expenditure of energy. Work is done on the plant by 

 energy received, and work is done by the plant in the main- 

 tenance of its various life-activities. The resultant effect 

 A — D is the difference between the uphill and downhill 

 work. The greater insight into the physiological mechanism 

 obtained from this wider outlook has led to the discovery of 



