in the temperature of ten degrees C!entigrade (16° F. ) . These 

 authors assurae the growth rate to be unity for a temperature 

 of A"^" ?. amd derive a series of values representing tempera- 

 ture efficiencies fir hi^-her temperature. In using these. ex- 

 ponential indices the assumption is made, as the authors have 

 pointei out, tha-^ the plant processes whose rela'^ion to tem- 

 "oerature is under investigation follow the chemical principle 

 upon v.'hich the indices are Lased. When this scheme is use:l, 

 the efficiency value for any temperature is represented by 



Tj (\r> 



the value of the exponential index that corresponds to^^ tem- 

 perature value itself. Assumi ng t"hie growth ra-^e to be unity 

 for a temperature fo 40'* ?. , it should be 1.21 for a terar)e- 

 rature of 45°, 2.0 for 58°, etc. 



Since most of the tempera txires with which we ^-ave to deal 

 are belov/ the optimum for plant growth, since temperature and 

 the growth rate appear to be related in an approximately 

 linear manner between 40° ana the optimum, f about 32" C.) and 

 since both the exponental and remainder series of index values 

 increase in a practically linear way throughout this range, 

 both of the methods Just considered give temperature effi- 

 ciency numbers that appear to be approximately proportional 

 to plant growth as it is influenced by t^mperatxire . It is 

 of co-rse obvious that neither of these methods can properly 

 express efficiencies for temperatures above the optimum since 

 the.7 give numbers which continue to increase with increasing 

 temperature 7:hile growth increases with increasing tempera- 

 ture up to the optimum and then decreases .with higher tempe- 

 rature. Also, both these methods appear generally to give 



