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