xii CONTENTS. 



CHAPTER VII. 

 The Biology of Soil, ------ 56 



PAGE 



CHAPTER VIII. 

 Hybridisation and Selection, - - - . 69 



PART II. DISEASE IN PLANTS. 



CHAPTER IX. 

 Phytopathology. Derivation and Meaning, - 85 



CHAPTER X. 

 Health and Disease, - - - . . ^j 



CHAPTER XI. 

 i/Xauses of Disease, ------ 99 



^ CHAPTER XII. 



^ya;AUSEs OF Disease. The Living Environment, 108 



CHAPTER XIII. 



Nature of Disease, - - - - - - 119 



CHAPTER XIV. 

 Nature of Disease {Continued), - - - - 130 



