PC' 



LETl^ER OF TRANSMITTAL 



U. S. Department of Agriculture, 



Bureau of Plant Industry, 



Office of the Chief, 

 Washington, D. C, August 28, 1909. 



Sir: I have the honor to transmit herewith and to recommend for 

 pubhcation as Bulletin No. 165 of the series of this Bureau the accom- 

 panying manuscript entitled ''Application of Some of the Principles of 

 Heredity to Plant Breeding." This paper was prepared by Mr. W. J. 

 Spillman, Agriculturist in Charge of the Office of Farm Manage- 

 ment of this Bureau. Great progress has been made during the past 

 ten years in investigations relating to the principles involved in the 

 improvement of plant varieties and the production of new varieties 

 by cross-breeding. Thus far there has been no general statement 

 of the principles applicable in this work especially designed for the use 

 of the actual breeder. The present paper is an attempt to set forth 

 in an orderly manner what is known of the effect of selection on differ- 

 ent types of plants and the possibilities of cross-breeding for the pur-- 

 pose of producing new varieties, as understood by the author. 



The paper is submitted and recommended for publication in accord- 

 ance with the fixed policy of this Bureau of giving its men full oppor- 

 tunity of presenting results of scientific and practical interest from 

 different points of view. 



The author wishes to acknowledge the helpful criticism of Prof. 

 C. V. Piper, and especiall}^ of Assistant Secretary Willet M. Hays, 

 both of whom have carefully read the manuscript and have made 

 many valuable suggestions in the treatment of the various topics. 

 Respectfully, 



B. T. Galloway, 



Chief of Bureau. 



Hon. James Wilson, 



Secretary of Agriculture. 



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