Xll CONTENTS. 



Page 



On the Origin and Action of Humus . . .45 



Growth of Plants . . . . . . 49 



Transformations of Organic Substances . . 51 



Nature of Organic Chemical Processes . 53 



The use of Humus explained . . 59 



Humus is not indispensable for Plants . . 61 



Assimilation of Hydrogen . . . .63 



Hydrogen is obtained by the Decomposition of Water . 65 



Its assimilation is attended with the Evolution of Oxygen . 67 



On the Origin and Assimilation of Nitrogen . 69 



Source of Nitrogen in Plants . . . - 70 



Ammonia is always contained in the Atmosphere . . 73 



Use of Gypsum in manuring Meadow Land . . 87 



Use of burned Clay as Manure . . 89 



The Inorganic Constituents of Plants . . .92 

 Plants contain an invariable quantity of Alkaline 'Bases . 94 



The origin of common Salt in Plants . . .114 



The Art of Culture . . . . . 116 



Use of Humus . . . . . 1 18 



Nutrition and Growth of Plants . . . . 1 23 



Necessity of Azotised Substances . . .131 



Influence of the Food on the Produce . 133 



Composition of Soils . . . . .141 



The Fertility of Soils . . . . 145 



Fallow Crops . . . . . . J57 



The Interchange of Crops and Manure . 159 



Manure . .174 



