LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 

 Division of Vegetable Physiology and Pathology, 



Washington, D. C, September 28, 1899. 

 Sir: I respectfully transmit herewith a bulletin prepared by Dr. 

 Oscar Loew, of this Division, on the physiological role of mineral nutri- 

 ents. For several years Dr. Loew has been engaged in the study of 

 the functions of mineral nutrients in plants. This work has led into 

 new fields, and has resulted in discoveries which it is believed will be 

 of much practical value to agriculture. The importance of mineral 

 nutrients is so well known as to need little comment, but the part each - 

 plays in the life of an organism is still largely a matter of conjecture. 

 It is evident that we can not hope to understand nutrition until we 

 become better acquainted with the physiological action of the nutrients 

 themselves. The main object of this bulletin is to show what has been 

 accomplished in this direction, and to encourage and stimulate work 

 along the lines laid down. The matter has been prepared primarily 

 for teachers and experiment station workers, and is therefore treated 

 from a technical rather than a practical standpoint. I respectfully 

 recommend that it be published as Bulletin IN'o. 18 of this Division. 

 Kespectfully, 



B. T. Galloway, 



Hon. James Wilson, Chief of Division. 



Secretary of Agriculture. 



