CONTENTS XV 



Page 



2. Magnesium 186 



Physiological Effects of Magnesium 186 



Dolomite Vegetation 187 



Serpentine 188 



3. Iron 189 



4. Zinc, Copper 191 



5. Chloride, Sulphate, Soda (Salts of "Saline Soils") 191 



The Halophyte Problem 192 



Salt Constancy 194 



Vegetation of Sodium Chloride Soils 195 



Determination of Chloride Content 200 



Vegetation of Sulphate Soils 201 



Solfataras, Fumaroles 203 



Sulphur Formation by the Action of Bacteria 203 



Determination of Sulphates 203 



Soda Soils 204 



Determination of Soda 205 



Vegetation of Soda Soils 205 



CHAPTER VII 

 Edaphic ok Soil Factors: Physical 207 



1. Texture of the Soil 207 



Soil Granulation 207 



Determination of Particle Size: Mechanical Analysis of Soils 208 



Soil Dispersion and Vegetation 209 



Soil Crumbing 211 



2. Soil Water 211 



Available Water 212 



Water Capacity 213 



Coefficient of Soil Moisture 214 



Wilting Point and Wilting Coefficient 215 



Ground Water 217 



3. Soil Temperature 218 



Maximal Soil Temperatures 221 



Decrease of Temperature with Depth of Soil 222 



Measurement of Soil Temperature 223 



4. Soil Atmosphere 223 



Oxygen Content of the Soil 224 



Carbonic Acid Content of the Soil 225 



Pore Volume 226 



Air Capacity 227 



Actual Air Content 229 



Determination of Air Capacity 231 



Permeability 232 



CHAPTER VIII 



Soil Organisms 233 



Soil Fauna 233 



Soil Flora 234 



