PAGE 



CONTENTS 

 PART I 



CHAPTER I 



T* TV T JfAUS 



IHE NORMAL SOIL AND ITS REQUIREMENTS . 3 



CHAPTER II 

 SICK SOILS NOT INFLUENCED BY PARASITES . 23 



CHAPTER III 



SOIL SICKNESS DUE TO THE PRESENCE OF PARA- 

 SITES HARMFUL TO PLANTS . 4! 



CHAPTER IV 

 METHODS OF TREATING SICK SOILS ... 53 



PART II 



CHAPTER V 



THE HEALTHY HOST AND ITS REQUIREMENTS . 63 



CHAPTER VI 

 CAUSES OF DISEASES IN CROPS . . .71 



A. Diseases of a Mechanical Nature 



B. Diseases Due to Physiological Causes 

 c. Diseases of Unknown Origin 



XVll 



