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. 



physical explanation 



(Liebig), 154. 



Equations expressing : 



amount, 156. 



rate, 157. 



Acidity, effect on plants, 81. 



in soil, 109. 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, 



5i, 84- 



swamp soils assisted by algas, 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. 

 Algae 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 



