576 



Journal of Agricultural Research 



Vol. XX, No. 7 



The daily averages, the standard deviations, and the correlations are 

 given in Table I. 



Table I. — Daily averages, standard deviations, and correlations from experiments on 

 transpiration in crop plants made by Briggs and Shantz at Akron, Colo., IQI4 



CORRELATIONS 



Wind . 



Radiation 



Temperature 



Wet-bulb depression 



Evaporation 



Small grains 



Rye 



Sorghum, millet^ 



Sudan grass (in inclosure) 



Sudan grass (in open). . . . . 



Dent corn 



Algerian corn 



Cowpea, lupine c 



Alfalfa d 



Amaranthus 



Wind. 



-o. 01 ±0-07 



- . 02 ± . 07 



. 28 ± .06 



.38 ± .06 



.22 ± .04 

 . 19 ± .10 

 .2l8± 

 •52 ± 

 •32 ± 

 .28 ± 



•33 ± 

 •335± 

 . 290 ± 

 . 04 ± 



. 041 



.07 



.08 



.08 



.09 



•°57 



•03s 



. 10 



Radiation. 



o. 01 ±0.07 



570± 

 55 ± 

 52 ± 

 52 ± 

 62 ± 

 570± 

 430 ± 

 40 ± 



•°5 



.04 



•03 



.06 



.030 



.06 



.07 



.06 



.06 



. 042 



.030 



.09 



Temperature. 



-0.02 ±0.07 

 •47 ± -05 



• 59 ± -OS 

 .56 ± .05 

 .71 ± .02 



• 73 ± -°5 



• 653± .026 

 .84 ± .03 

 .81 ± .03 

 .71 ± -°4 



• 79 ± -04 



•675± 

 •495± 

 •45 ± 



.035 

 029 



oS 



Wet-bulb 

 depression. 



28 ±0.06 

 48 ± -05 

 59 i -OS 



83 ± 

 88 ± 

 94 ± 

 788 ± 

 83 ± 

 85 ± 

 81 ± 

 88 ± 

 785± 

 7oo±. 

 60 ± 



. 02 

 • 025 

 019 



Evapor- 

 ation. 



o. 38 ±0. 06 



.68 ± .04 



.56 ± .05 



-.83 ± .02 



87 ± .02 

 91 ± .02 

 7I3± -° 21 

 93 ± .01 

 82 ± .03 

 79 ± -°3 



• 8 S ± 



• 775± 



• 705 ± 



• 56 ± 



•03 

 .025 

 . 019 

 .06 



Mean. a 



Evaporation (shallow tank) (kilograms per square meter) 9. 70 2. 76 



Integrated radiation (calories per square centimeter) 753 134 



Air temperature, integrated mean (degrees Centigrade) 20. 10 3. 48 



Integrated wet-bulb depression (hour degrees, Centigrade) 143 5 8 



Wind velocity (miles per hour) 5-54 2. 24 



a Averages x>i six similar correlations involving Kubanka and Galgalos wheat, Swedish Select and Burt 

 oats, Hannchen barley, and spring rye. The last, having on the whole the largest correlations, is also given 



SC ft Averages of four correlations, Minnesota Amber and Dakota Amber sorghum and Kursh and Siberian 

 Millet. These correlations were all very similar. 



« Average of the similar correlations for cowpeas and lupine. 



<* Average of four tests with alfalfa. 



* Published as + 0.80, which seems too large. Recalculation gives + 0.52. 



It will be interesting first to com- 

 pare the direct and indirect methods 

 of calculating path coefficients and 

 coefficients of determination. Let us 

 consider the relations of wet-bulb 

 depression (B) to temperature (T), 

 wind velocity (W), and radiation (R). 

 Since the direct methods are only 

 applicable in systems in which each 

 variable is connected with every 

 other variable, the diagram of rela- 

 tions is as shown in figure 14. 

 Outstanding factors, independent of 

 W, R, and T are represented by O. 



*^M. 



Fig. 14. — Relations between wet-bulb depression 

 (B), wind velocity (W), radiation (R), and tem- 

 perature (T) as assumed for direct analysis. 



