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ILLINOIS ACADEMY OF SCIENCE. 



lines; hence the amount of water available for the purposes of 

 growth is shown by the interval between the graphs representing 

 the soil moisture and the line representing the wilting coefficient. 

 The wilting coefficient will be found to vary considerably in the 

 different locations dependent largely upon the amount of humus 

 present in the soil. Thus, in the depression, it is seen to be 18.9 

 at 7.5 cm. (Fig. 4B) below the surface, but only 12.5 at 25 cm. 

 (Fig. 4D), due to more humus in the surface layers. The abun- 

 dance of the water supply in this locality is seen by the very 



Figure 4. Graphs representing the range of soil moisture throughout 

 the growing season, at 7.5 cm. (A) and at 25 cm. (C), below the surface, 

 in the depression in the oak-hickorv forest, and the wilting coefficients 

 (B, D) at these depths. 



