Bulletin No. 18. v. p. P- 



U. S. DEPARTMENT OF AGRICULTURE. 



DIVISION OF VEGETABLE PHYSIOLOGY Al^D PATHOLOGY. 



B. T. OALLOWAY, CHIEF. 



THE 



PHYSIOLOGICAL ROLE OF MINERAL NIITRIENTS 



OSCAR LOEW, 



OF THE 



Division of Vegetable Physiology and Pathology 



WASHINGTON: 



GOVERNMENT P R I N '1' T N G O F F I C E . 

 I 899. 



