VI 



Contents. 



SECTION IV 

 RELATION OF BACTERIA TO SOILS 



CHAPTER XIX Relation of Bacteria to Fertility 171 



XX Effect of Bacteria on Minerals of the Soil 183 



XXI Ammonification, Nitrification, and Denitrifi- 



cation 186 



XXII Fixation of Nitrogen 195 



XXIII Bacteria in Manures ^ . . . 207 



XXIV Water Supply and Sewage Disposal 214 



SECTION V 



FOOD PRESERVATION AND DISEASES OF PLANTS 



CHAPTER XXV Preservation of Foods 225 



XXVI Diseases of Plants 235 



