viii PREFACE. 



Our aim has been to present actual experimental 

 work in every phase of the subject possible, and 

 to state the directions for such work so that the 

 student can perform it independently of the 

 teacher, and to state them in such a way that 

 the results will not be suggested by these direc- 

 tions. One must perform the experiment to 

 ascertain the result. 



Any energetic teacher can, by carefully going 

 over the work in advance, working out the ex- 

 periments himself and reading the references, be 

 able to do creditable class work if he is willing 

 to " dig," but it is useless for any one else to 

 undertake to be an agriculturist or to teach 

 agriculture. 



Every available source has been drawn upon 

 for the material used in this book, but the plan 

 of presenting it is original, as well as most of 

 the experiments and exercises, and many practi- 

 cal ideas gained from experience in teaching. 



We wish to express our grateful appreciation 

 to all those who have so kindly helped us by 

 reviewing the manuscript or by loaning us illus- 

 trations. 



The following persons from the United States 

 Department of Agriculture at Washington have 

 been very helpful: The manuscript was examined 

 by B. T. Galloway, Chief of the Division of 

 Plant Industry ; W. J. Spillman, Agrostologist ; 

 A. F. Woods, Pathologist and Physiologist ; 



