viii PREFACE 



Experiment Stations and of the United 

 States Department of Agriculture. 



The book is offered with a full conscious- 

 ness of its shortcomings, but with the hope 

 that it may be of some definite service and 

 that it may serve as a focusing point for 

 criticisms and suggestions, out of which 

 may be born a fuller knowledge through the 

 experience and observation of its readers. 



W. J. WRIGHT. 

 New York State 

 School of Agriculture, 1917, 

 Alfred, New York. 



