582 



Journal of Agricultural Research 



Vol. XX, No. 7 



The following four equations can be made with which to solve the 

 path coefficients from W, H, R, and T to X: s 



r XB =w f r jm + t'r 6T + u f r m + h'r m . 



Substituting the values already found for a, b, c, d, w, h, t, and r BH > 

 we have 



y xw = + i.oow' — 0.022' — O.OIM' 

 r xT = — .02w'+ 1.00/'+ -47u' + 0.3706/?' 

 r XR = — .01 w' + -47^'+ loom'— .0761/1' 

 r XB = + .28w'+ .59*'+ .48M'— .4784/1'. 



The solution is as follows : 



w' = Px'yr= + 0.9971 r xw + o.oi43r XT —o.oo22r XB + 0.01 1 4r XB 



t' = Px-T =— .2207r xw + .8943r xT — .8175^ + .8228r XB 

 u' = Px- R = + .i488r xw — .3633^+1.4155^— .5067^ 

 h' = p x . u -+ .4607*^ + .7468^+ .4107^— 1.5772^. 



It is merely necessary to substitute the values of the correlations of 

 evaporation or transpiration with wind velocity, temperature, radia- 

 tion, and wet-bulb depression, as 

 given in Table I, to find the four 

 path coefficients in each case. The 

 results are given in Table II. These 

 have all been checked by substitu- 

 tion in the fourth equation (r XB = + 

 o.28ie/ +0.59^' + 0.48M'— 0.4784/1'). 

 Thecorrelationbetween evaporation 

 and the transpiration of any plant 

 can be deduced from the formula 

 r XE = wVbw + t'r ET + mV er 4- feVuH. 

 The correlations of evaporation with 

 wind velocity, temperature, and 

 radiation have been given in Table I 

 as 0.38, 0.56, and 0.68, and that 

 with humidity can be calculated by the formula r EU = p E . K + ap E .- R + 

 dp K . T =— 0.2651. Thus r XE = 0.38W' +0.56^' + o.68m' — 0.2651/1'. The 

 calculated results in column 6 of Table II are compared with actual 

 correlations between evaporation and transpiration in column 7. The 

 correlation of evaporation with itself comes out 0.839 by this for- 

 mula. There should, however, be an additional term (p x -o^Eo) m the 

 formula to allow for correlation through other factors (O) than W, T, 

 R, and H. From Table III we find that evaporation is determined 



Fig. 16. — Relations between evaporations or trans 

 piration (..V) and the system shown in figure 15. 



