X CONTENTS 



CHAPTEE XI. 

 SULPHUR-BACTERIA : IRON-BACTERIA 



SECTION PAOE 



Sulphur-Bacteria : 



1. Introduction to Sulphur-Bacteria 144 



2. Classification op the Sulphur-Bacteria 145 



Beggiatoa, Thiothrix, Thiophysa, and Purpur-baoteria. 



3. The Physiology op the Sulphur-Bacteria 149 



Iron-Bacteria : 



4. Introduction to Iron-Bacteria - - 151 



Crenothrix polyspora : Cladothrix dichotoma : Leptothrix oohraoea. 

 Gallionella ferruginea ; Clonothrix fusoa : Spirophyllum ferru- 

 gineum. 



5. The Physiology of the Iron-Bacteria, 160 



CHAPTEE Xll. 



BACTERIA AND THE PRESERVATION OF FOOD-PRODUCTS 



1. Introduction 162 



2. First Method of Food-Preservation— Destruction op Micro- 



organisms - 164 



3. Second Method — Dryinq - - 165 

 4 Third Method— Cooling 167 



5. Fourth Method — Use of Chemicals - 168 



6. Preservation of Eggs - - 169 



CHAPTER XIII. 

 THE NITROGEN-BACTERIA 



1. Introduction 171 



2. Activities of Nitrogen-Bacteria when Free in the Soil 172 



3. Conditions of Nitrogen-Fixation - - 175 



4. Nitrogen-Bacteria acting in conjunction with Leguminous 



Plants - 177 



