represents the averajre daily value. All of the data hnre 

 treated, both plant and climatic, have been reduced to daily 

 rates, for reasons which will be given below. 



McLean has pointed out three ways in which we may use 

 the daily raaximtun and minimum temperature record and a tempe- 

 rature coefficient, such as the Livingston Physiological index, 

 to get average daily temperature ef ilciencies for growth per- 

 iods. (1) We may add "^he maximum imd minimum for each da"^, 

 divide by two to get the mean temperature for the day, and 

 average the daily means thus obtained to ^et an average daily 

 mean for the period in question. (This gives the aeries of 

 numbers shown in the tables of climatic data, line 5.) The 

 physiological index corresponding to the average daily mean 

 for the period may then be taken as the temperatxire efficiency 

 for the period., (Z) We may sum the physiological indices 

 Corresponding to each of the daily means, divide this sum by 

 the number of days in the period and thus get an average daily 

 index to represent the temperature efficiency for the period. 

 (3) Lastly, we may average the indices corresponding to the 

 maximum and minimum for each day, thus obtaining an avera^-e 

 daily index, add these average daily indices, and divide the 

 sum by the number of daj^'S in the neriod as was done in the 

 proceeding case to get an average daily index, '"he first 

 method takes account only of the variations between periods, 

 the second involves the differences between periods and the 

 interdiurnal variations, while the third takes account of 

 both differences between periods and the interdiurnal varia- 

 tions and also invor'''Q5s the daily range of temperature. Only 



