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ILLINOIS ACADEMY OF SCIENCE. 



soil is indicated by the smaller wilting coefficients, y.j and 8.5 

 per cent (Fig. 5). The amount of water available for growth is 

 also less, and once at 25 cm. and twice at 7.5 cm. it fails. The 

 greater fluctuation in the supply at the higher level is very evi- 

 dent at this station (Fig. 5A), but is also apparent in the other 

 localities (Figs. 4A and 6A). Here the surplus supply for the 

 ten weeks from July ist averages 4.6 per cent at 7.5 cm. and 4.1 

 per cent at 25 cm. 



The soil records at the grazed station are noticeable for their 

 great range, and for the deficiency in the supply at the 7.5 cm. 

 level (Fig. 6). Here during the ten critical weeks of midsummer 



25cm. 



Figure 6. Graphs representing the range of soil moisture at 7.5 cm. 

 (A) and at 25 cm. (C) below the surface, in the grazed oak-hickory forest, 

 and the wilting coefficient (B, D) at these depths. 



