SUBJECT INDEX. 



Absorption compounds in soil, 104. 



— of nutrients by plants, 296, 357. 



substances by soil, 17, 149 et seq. 



chemical explanation 



(Way), 153. 

 — ^' colloidal explanation, 



155. 



combined chemical 



and physical ex- 

 planation (Knop), 



154. 

 —r- physical explanation 



(Liebig), 154. 



Equations expressing : 



amount, 156. 



rate, 157. 



Acidity, effect on plants, 81, 



— in soil, log. See also Soil Acidity. 



— — atmosphere, effect on plants, 82. 



— methods of studying ; hydrogen ion 



concentration, 113 ; titration, 113. 

 Acids, dilute, action on soil, 157 et seq., 



234- 

 use in soil analysis, 234, 334. 



— effect on activity of micro-organisms 



in soil, 268. 

 plant growth, 81, 268. 



— supposed excretion by plant roots, 



16, 233. 

 Actinomyces in soil, 259. 



— producers of humus, 177. 

 Adsorption, 156. 



— equation expressing, 149, 156. 

 Aeration of soils, effect on plant growth, 



51, 84. 



— swamp soils assisted by algae, 256. 

 Agricere, 282. 



Agriculture, early literature of, i. 

 Air, effect on plant growth, 9. 

 of vegetation on, 8, 10, 20. 



— in soil, composition of, 227. 

 volume of, 220, 



— supply to plant roots, 51. 



in swamp soils, 256. 



Algas in soils, 254. 



Alkali soils, 74, 86, 94, 



Alkali soils, bacterial activity, 274. 

 Alkalis necessary for plant growth, 15, 

 18. 



— supposed production by plants, 8, 10. 

 Alumina in soil, 338. 



Aluminium, beneficial in small quan- 

 tities, 56, 75. 



— harmful in larger amounts, 84. 

 Amino-acids produced in soils, 185. 

 Amino-nitrogen in soils, 147. 

 Ammonia, assimilation by algae, 256. 

 fungi, 259. 



micro-organisms, 210 et seq. 



plants, 57. 



— in soil, determination of, 349. 

 amount of, 146. 



— nutritive value to plants, 58. 



— production in soil, 185 et seq. 



organisms effecting, 187. 



by fungi, 259. 



— toxic effects in larger quantities, 58, 



80. 

 Ammonifying power, 263. 

 Ammonium salts, absorption by soil, 



155 et seq. 



— sulphate acidifies soil, 116. 

 Amoebae in soil, 289 et seq. 

 Analysis of plant ash and study of plant 



nutrients, 7. 

 soil and manurial requirements, 



326, 334- 

 mechanical and chemical 



contrasted, 342. 



methods of, 347. 



Antagonism of ions (bacteria), 274. 



(plants), 79. 



Arid conditions, value of phosphates in, 

 65. 



— soils, comparison with humid : 



mineral composi- 

 tion, 100. 



organic matter, 139. 



Arsenic compounds, effect on micro- 

 organisms, 84. 



plant growth, 84. 



oxidation by bacteria, 84. 



395 



