226 



ENVIRONMENTAL CONDITIONS. 



Table 7. — Summation of normal daily indices of temperature efficiency for plant growth, 

 for the period of the average frostless season. (Plates 39 and 40.) 



[The mean daily efficiency indices are derived from the corresponding temperature indices, (1) 

 by the exponential equation of chemical reaction velocities and (2) by the empirical growth- 

 rate coefficients for maize seedlings as found by Lehenbauer for a 12-hour exposure to 

 maintained temperature. The temperature efficiency for 40° F. is taken as unity in both 

 cases. 1 



