In the years of their seventy-fifth and seventieth 



anniversaries respectively, this book is dedicated 



to Professors 



M. W. BEIJERINCK 



and 

 S. WINOGRADSKY 



the investigators who have thrown the first UgJd 

 upon some of the most important soil proc- 

 esses and whose contributions can 

 well be considered first and fore- 

 most in the science of Soil 

 Microbiology 



