Acknowledgments are due to the one thousand or more farmers 

 without whose cooperation the work could not have been done ; 

 to Professor John Craig, at whose suggestion I undertook the 

 work, for many helpful suggestions and for reading the manu- 

 script and proof ; to Director L. H. Bailey for many valuable 

 suggestions and for reading the proof ; to Mr. Christian Bues, 

 who was my co-worker in the field work in Orleans County, 

 and who read the manuscript of Part I ; to Mr. Cornelius Betten 

 for reading the manuscript ; and to Professor Bonsteel and Mr. 

 Whetzel for reading parts of the proof. 



Figures 44, 48, 75, 78, 79, 82, 92 and the figures in Part II 

 were furnished by the Department of Horticulture. Figure 85 

 was furnished by Professor Slingerland. 



380017 



