PERMANENT WILTING IN PLANTS 105 



Ciliated from the Briggs and Shantz formula. It appears here 

 also that there can be no range Of low evaporation intensities 

 within which this factor is without marked effect upon the mag- 

 nitude of the soil moisture residue, unless indeed this range be 

 Ihnited to evaporation intensities very closely approaching zero; 

 the curve of these data, like that of the data of series I, is per- 

 sistently convex upward and approaches a vertical line for small 

 values of the evaporation rate. Furthermore, these results agree 

 with those of the preceding series in showing that the relative 

 efTect of alteration in the evaporation rate, upon the magnitude 

 of the moisture residue, becomes small with the highest rates 

 here dealt with. • 



It is obviously not legitimate here to attempt to pass a curve for 

 all five main averages through the points representing the first 

 two, as it was found to be possible in the case of series I. Ap- 

 parently such a generalized curve should pass below the points 

 for averages (3) and (5) and above those for averages (2) and (3) . 

 The curve shown in figure 2 is a logarithmic one, similar to that 

 of figure 1, passing through the point for average (1) and ful- 

 filling the conditions just stated for the remaining four. The 

 constant geometrical ratio is here taken again as 2, but the con- 

 stant arithmetical difference is 0.32, instead of 0.5 per cent, as in 

 the former case. All data being considered, it appears that this 

 generalized or theoretical curve represents fairly well the relations 

 concerned, albeit the graph of figure 2 is not as satisfactory 

 as that of figure 1. The only known fundamental difference 

 between the determining conditions of the present series and 

 those of series I lies in the fact that series I employed Zea and 

 series II employed Phaseolus plants. The other experiments of 

 this study throw no light upon the question thus raised. 



Series III. The soil mixture employed in this series was 

 identical with that used in the two series just discussed, but the 

 containers had each a capacity of two liters, four times the ca- 

 pacity of the cylinders used in the preceding and subsequent se- 

 ries. Capsicum plants were here used, one plant in each culture. 

 They were nearing maturity, some being in bloom at the time of 

 wilting while others were in the process of fruit formation. The 





