Chapter 1

PAGE Beginning of agricultural chemistry 4 Early theories regarding plant-growth 4 Van Helmont 4 Digby 6 Duhamel and Stephen Hales 8 Jethro Tull 9 Charles Bonnet's discovery of source of plants' carbon 11 Researches of Priestley, Ingenhousz, Senebier, on assimilation of carbon 11-12 Publication of first English treatise by Earl Dundonald 13 Publication of Theodore de Saussure, 'Chemical Researches on Vegetation,' 1804 14 Theories on source of plant-nitrogen 15 Early experiments on this subject 16 Sir Humphry Davy's lectures (1802-1812) 17 State of agricultural chemistry in 1812 17 Beginning of Boussingault's researches (1834) 21 Publication of Liebig's first report to the British Association 24 Refutation of "humus" theory 26 Liebig's mineral theory 26 Liebig's theory of source of plants' nitrogen 27 Publication of Liebig's second report to British Association 30 Liebig's services to agricultural chemistry 31 Development of agricultural research in Germany 32 The Rothamsted Experiment Station 33 Sir J. B. Lawes and Sir J. H. Gilbert, the nature and value of their experiments 33 Review of the present state of our knowledge of plant-growth 36 Proximate composition of the plant 36 Fixation of carbon by plants 37 Action of light on plant-growth, Dr Siemens' experiments 38 Source of oxygen and hydrogen in the plant 39-40 Source of nitrogen in the plant 40 Relation of the free nitrogen to leguminous plants 42-44 Relation of nitrogen in organic forms, as ammonia salts, and nitrates to the plant 46-50 Nitrification and its conditions 51 Ash constituents of the plant 53 Methods of research for ascertaining essentialness of ash constituents of plants 53 (_a_) Artificial soils, (_b_) water-culture 53-55 Method in which plants absorb their food-constituents 55 Endosmosis 55 Retention by soils of plant-food 57 Causes of retention by soils of plant-food 59 Manuring 60 "Field" and "pot" experimentation 60