No. 502] CHEMICAL MECHANICS IN LIVING PLANT 655 



one. Rise of temperature affects nearly all physical and 

 chemical properties, hut none of these is so greatly 

 affected by temperature as is the velocity of chemical re- 

 action. For a rise of 10° C. the rate of a reaction is gen- 

 erally increased two or three fold, and this has been gen- 

 eralized into a rule by van 't Hoff . As this increase is re- 

 peated for each successive rise of 10° C. either by the 

 same factor or a somewhat smaller one, the acceleration 

 of reaction-velocity by temperature is logarithmic in 

 nature, and the curve representing it rises ever more and 

 more steeply. Thus keeping within the vital range of 

 temperature a reaction with a temperature factor of X 2 

 per 10° C. will go sixteen times as fast at 40° C, as at 

 0° C, while one with a factor of X 3 will go eighty-one 

 times as fast. 



This general law of the acceleration of reactions 

 by temperature holds equally for reactions which 

 are being accelerated by the presence of catalysts. 

 As we regard the catalyst as merely providing 

 for the particular reaction it catalyzes, a quick way round 

 to the final stage by passing through the intermediate 

 stage of forming a temporary addition-compound with the 

 catalyst itself, so we should expect rise of temperature 

 to accelerate similarly these substituted chemical reac- 

 tions. 



It' this acceleration is a fundamental principle of chemi- 

 cal mechanics it is quite impossible to see how vital chem- 

 istry can fail to exhibit it also. 



Acceleration of Vital Processes by Temperature. 



At present we have but a small number of available 

 data among plants to consider critically from this point of 

 view. But all the serious data with which I am ac- 

 quainted, which deal with vital processes that are to be 

 considered as part of the protoplasmic catalytic congeries, 

 do exhibit this acceleration of reaction-velocity by tem- 

 perature as a primary effect, 11 



