638 
Journal of Agricultural Research 
Vol. V, No. 14 
Tabi/E XXXVII .—Correlation between transpiration and environmental factors 
Plant, period, and 
components. 
Correlation 
coefficient. 
Plant, period, and 
components. 
Correlation 
coefficient. 
Alfalfa (long period, Sept. 
Alfalfa (June 18, 19, 21, 
10 to Oct. 20, 1914): 
1914)—Continued. 
Radiation and trans- 
Wind velocity and 
piration. 
O. 840 ±0. 009 
transpiration. 
O. 626±0. 036 
Temperature and 
Wind velocity and 
transpiration. 
. 8l9± -. Oil 
radiation. 
. 641± . 046 
Wet-bulb and trans- 
Vertical radiation 
piration. 
. 822 ± . on 
and transpiration.. 
. 8i8± . 013 
Evaporation and 
Amaranthus (July 7 to 9, 
transpiration. 
. 8381b . on 
I 9 I 4 ): 
Wind velocity and 
Radiation and trans- 
transpiration. 
. 4851b . 026 
piration. 
. 844± . 016 
Wind velocity and 
Temperature and 
radiation. 
.30 2 ± .030 
transpiration. 
. 849± . 016 
Alfalfa (Oct. 16 to 20, 
Wet-bulb and trans- 
1914): 
piration. 
. 8421b . 016 
Radiation and trans- 
Evaporation and 
piration. 
. 886± . 010 
transpiration. 
. 9461b . 006 
Temperature and 
Wind velocity and 
transpiration. 
. 859± . 012 
transpiration. 
. 683 ± .031 
Wet-bulb ana trans- 
Wind velocity and 
piration. 
. 843 ± .013 
radiation. 
.7761b . 032 
Evaporation and 
Vertical radiation 
transpiration. 
. 9291b . 006 
and transpiration... 
.863 d: .014 
Wind velocity and 
Rye (Tune 22 to Tuly 3, 
transpiration. 
• 353 ± -039 
Wind velocity and 
Radiation and trans- 
radiation. 
• 275 :b .084 
piration. 
. 8201b . 014 
Vertical radiation 
Temperature and 
and transpiration.. 
, . 862 ± . on 
transpiration. 
. 8541b . on 
Alfalfa (Tune 18, 10, 21, 
Wet-bulb and trans- 
1914): 
piration. 
. 748 ± . 018 
Radiation and trans- 
Evaporation and 
piration. 
. 86i± . 015 
transpiration. 
. 894±. 033 
Temperature and 
Wind velocity and 
transpiration. 
. 7881b . 021 
transpiration. 
• 376± . 036 
Wet-bulb and trans- 
Wind velocity and 
piration. 
. 852± . oc8 
radiation. 
• 353 ± -°47 
Evaporation and 
Vertical radiation 
transpiration. 
. 888db . 012 
and transpiration.. 
. 766lb • 017 
An inspection of the correlation table will show that, excluding evapo¬ 
ration, the highest correlation is obtained between radiation and trans¬ 
piration. The correlation coefficient for these components is remarkably 
uniform for the different crops and periods, ranging from 0*82 to 0.88, 
the lowest value occurring in the case of rye, as one might expect from 
the form of the transpiration graph. 
The similarity in the form of the composite graphs for air temperature 
and wet-bulb depression would lead to the expectation that their correla¬ 
tion coefficients with transpiration would be similar and the coefficients 
are in fact nearly the same. The only exceptions are (1) alfalfa (June 
period), in which the wet-bulb depression shows the higher correlation 
with transpiration; and (2) rye, in which temperature is the more closely 
