90 



BULLETIN 1059, U. S. DEPARTMENT OF AGRICULTURE. 



5. It is to be noted that the percentage of variation of individual 

 cases is slightly less when the final (diagram 5) rather than the mean 

 wilting coefficient of each soil is taken. On the other hand, there is 

 considerably more spread between the two groups on this basis. It is 

 believed that the slightly poorer showing made by using the mean 

 wiltino- coefficient is due to the fact that losses caused primarily by 

 fungi were entirely eliminated from the calculations. With care 

 in this respect, the mean value for all the seedlings is undoubtedly 

 the more dependable and also more expressive. It should be noted 

 in this connection that in a group of 100 seedlings the weakest usually 



give a wilting coefficient twice as high as that indicated by the final 

 wilting, and not infrequently three times as high. 



6. The comparison of wilting coefficients with moisture equiva- 

 lents shows a wide gap between the two groups. The value of the 

 moisture equivalent data will be discussed later. 



7. While these results, all obtained at practically the same time 

 and in soils which showed no great chemical activity, indicate a use- 

 ful parallelism between wilting coefficient and capillary moisture, it 

 should be pointed out that the wilting coefficient may occasionally 

 go out of bounds as the result of acidity or alkalinity, so that any of 

 the physical tests on soils, taken alone, are quite worthless. It should 

 not be surprising to obtain wilting coefficients twice as great, relative 

 to capillarity, as those indicated above, especially with the pines. 



