258 SOILS: PROPERTIES AND MANAGEMENT 



Relation of the Wilting Point to the Hygroscopic Co- 

 efficient. BltlGGS AND SHANTZ l 



179. The wilting coefficient of plants. — It has been 

 known for many years that the common plants possess 

 different capacities for resisting drought. This has 

 usually been ascribed to one or more of three causes: 

 (1) difference in root extensions; (2) difference in ability 

 to become adjusted to a slow intake of water ; and (3) dif- 

 ference in pulling power against the viscosity of the water 

 film. The last two capabilities would argue for different 

 wilting coefficients for different crops on the same soil. 

 The most extended work on this subject has been by 

 Briggs and Shantz, 2 who found that the permanent wilting 

 point in a saturated atmosphere is practically the same 

 for all plants. Later Caldwell 3 demonstrated that this 



1 Briggs, L. J., and Shantz, H. L. The Wilting Coefficient 

 for Different Plants and its Indirect Determination. U. S. 

 D. A., Bur. Plant Indus., Bui. 230, p. 65. 1912. 



2 Briggs, L. J., and Shantz, H. L. The Wilting Coefficient 

 for Different Plants and its Indirect Determination. U. S. 

 D. A., Bur. Plant Indus., Bui. 230. 1912. 



3 Caldwell, J. S. The Relation of Environmental Condi- 

 tions to the Phenomenon of Permanent Wilting in Plants. 

 Physiological Researches, Station N, Baltimore. U. S. D. A., 

 Vol. I, No. 1. . July, 1913. 



