CONTENTS xi 



Number of Bacteria in Soil 161 . 



Factors Influencing Number .... 162 



Kinds of Microorganisms in Soil . 164 



B. megatherium de Bary . 165 



Morphology 165 



Cultural Characteristics 165 



Physiology 165 



B. mycoides Fltigge, 1886 166 



Morphology 166 



Cultural Characteristics 167 



Physiology 167 



B. cereus Frankland, 1887 167 



Morphology .... 167 



Cultural Characteristics 167 



Physiology 168 



Ps. fluorescens (Fliigge) Migula . 168 



Morphology ... 168 



Cultural Characteristics 168 



Physiology 168 



Actinomyces .... 169 



Reference 170 



CHAPTER XVII. 



MINERALIZATION AND SOLVENT ACTION OF BACTERIA 



Bacteria as Soil Formers 171 



Calcium Carbonate 172 



Phosphorus . 173 



Sulphur .... 178 



Iron 180 



Potassium 180 



References 180 



CHAPTER XVIII. 



THE CARBON, NITROGEN, SULPHUR AND PHOSPHORUS CYCLES 



The Carbon Cycle 182 



The Nitrogen Cycle 183 



The Sulphur Cycle . 184 



The Phosphorus Cycle ' 184 



References 187 



CHAPTERS XIX. 



PUTREFACTION, FERMENTATION AND DECAY 



Definitions 188 



Active Agents 189 



Chemistry of the Process 192 



References . 193 



CHAPTERS XX. 



AMMONIFICATION 



Species and Distribution 196 



Methods 198 



Material Ammonified 199 



Influence of Soil and Climatic Conditions 200 



Moisture 200 



Aeration 202 



Lime and Magnesium 203 



Phosphorus 203 



Chemistry of the Process 204 



References . ... 207 



