CONTENTS. 



rios 



Object of the Work --_----. i 



PART THE FIRST. 



ON THE CHEMICAL PROCKSSES IN THE NUTRITION OF VEGETABLES. 



CHAPTER 



I. — The Constituent Elements of Plants ----- 3 



II. — The Origin and Assimilation of Carbon 5 



III. — On the Origin and Action of Humus ----- 28 



IV. — On the Assimilation of Hydrogen 35 



V. — On the Origin and Assimilation of Nitrogen 40 



VI.— On the Source of Sulphur 58 



VII. — Of the Inorganic Constituents of Plants 64 



VIII. — On the Formation of Arable Land ----- 81 



IX.— The Art of Culture 93 



X.-rOn Fallow 123 



XI.— On the Rotation of Crops - - 133 



XII. — On Manure - - 166 



XIII.— Retrospective view of the Preceding Theories - 186 



Supplementary Chapters. — The Sources of Ammonia - - 205 



Is Nitric Acid food for plants ?----- 214 



Does the Nitrogen of the Air take part in Vegetation ? - 223 



Giant Sea-weed -------- 225 



Appendix to Part I. ---_.___ 227 



Experiments of Wiegmann and Polstorf - - - 227 



and Analyses of Boussingault - - - 231 



Analyses of Hertwig 238 



Fresenius - - - - . - - 239 



Berthier 240 



De Saussure ------ 242 



Recent Analyses of the Ashes of Plants - - - 247, 254 



Analyses of Animal Excrements 255 



Urine ........ 256 



Guano ....... 258 



Marl ...... .264 



Ammonia in the Soil 264 



