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Journal of Agricultural Research 
Vol. VII, No. 4 
however, show the same relative dependence of transpiration upon the 
physical factors. Wet-bulb depression and evaporation (shallow tank) 
exhibit the highest correlation with transpiration in all cases, while wind 
velocity is correlated with transpiration to a very slight extent at Akron. 
The degree of dependence of transpiration of the small grains in 1914 
upon radiation, temperature, wet-bulb depression and wind velocity, 
considered as independent causative factors, as shown by the squares of 
the correlation coefficients is as follows: Wet-bulb depression, 0.77; 
temperature, 0.50; radiation, 0.42; and wind velocity, 0.05. Since the 
sum of these squares exceeds unity, the physical factors are evidently 
intercorrelated. The association of transpiration of the small grains 
with evaporation (shallow tank) is 0.76, or the same as with wet-bulb 
depression. 
