REACTIONS IN LIVING MATTER 



result that the velocity of reaction is doubled or 

 trebled when the temperature increases by 10 

 degrees. This rule, well known to the chemists 

 of our days as Van 't Hoff's Rule or the R.G.T.- 

 Rule, is in practice applicable between the ex- 

 tremes of - 50 and 300 degrees. Below and above 

 these extremes the quotient is larger than 3 or 

 smaller than 2. It is of great interest to see that 

 chemical reactions in plants strictly follow the 

 same rule. F. F. Blackman and Miss Matthaei 

 showed that the dependence of the carbon- 

 assimilation of leaves in sunlight upon the tem- 

 perature is an exact example of Van 't Hoff's Rule. 

 Blackman stated the same for the respiration of 

 plants. Kanitz drew attention to many former 

 observations of different authors which demon- 

 strate quite sufficiently that the R.G.T.-Rule is avail- 

 able for protoplasma-streaming, geotropism, longi- 

 tudinal growth, pulsation of vacuoles in cells, etc. 



As well as the influence of temperature on 

 chemical reactions, the influence of the physical 

 condition of the reacting substances is an old 

 laboratory experience : Corpora non agunt nisi 

 fluida. The chemist is accustomed to dissolve 

 the substance which is to be used in an experiment 

 to react on other substances. The chemical course 

 in living cells is the same. All substances destined 

 for reactions are first dissolved. No compound is 

 taken up into living cells before it has been dis- 

 solved. So the mineral salts of soil, the organic 

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