CONTENTS 



INTRODUCTION n 



Apparatus for One Student 1 1 



Literature 12 



Laboratory Rules 14 



EXERCISES IN SOIL BACTERIOLOGY 16 



Number of Microorganisms in Soil 16 



Relation of Microorganisms to the Nitrogen Cycle 35 



Relation of Microorganisms to the Carbon Cycle 75 



Relation of Microorganisms to the Sulphur Cycle 81 



Relation of Microorganisms to the Iron Cycle 84 



Relation of Microorganisms to the Physical Properties of Soil.. . . 87 



FORMULA AND METHODS 88 



Cleaning Glassware 88 



Preparation of Culture-media 89 



Media for the Determination of the Number and for the 



Separation of Soil Bacteria 89 



Counting Soil Protozoa 97 



Ammonification 9 8 



Nitrification 100 



Denitrification 106 



Nitrogen Assimilating Organisms 108 



Cellulose Destroying Organisms in 



Sulphur Organisms 116 



Iron Organisms 118 



Yeasts 119 



Fungi 1 20 



Actinomycetes 122 



Algae 123 



Higher Plants 124 



Preparation of Stains 127 



Preparation of Reagents and Qualitative Methods of Analysis. . . 133 



Quantitative Methods of Analysis I4 1 



Special Methods i5S 



INDEX 165 



9 



