SUBJECT INDEX 



401 



Nitrification, supposed chemical origin, j Nitrogen in soils, percentage present, 



335. 



relation to fertility, 334. 



Nitrogenous nutrients for plants, 18, 



22, 57. 

 Nodule organism, artificial culture of, 



204, 206. 

 entry into plant, 205. 



— — isolation from soil, 205. 

 life cycle, 204. 



— — specific nature of, 25. 

 stimulated by manganese com- 

 pounds, 207. 



Nodules on roots of leguminosae con- 

 tain bacteria, 21, 25, 



Normal conditions in heavy soil, 249. 



Nutrient solution, effect of concentra- 

 tion on plant growth, 238. 



Nutrients become toxic when given in 

 larger quantity, 56. 



— needed in large quantities, 56. 

 small quantities only, 56, 



236. 



— quantity absorbed by plants from 

 soil, 284, 357. 



— raw materials out of which plant 

 food is made, 55. 



Nutrition of plants, effect of water 

 supply, 38 et seq. 



Nutritional disturbances in plants, 236, 

 304- 



23- 



— two stages demonstrated, 23, 188. 

 Nitrifying power, 262, 300. 

 Nitrites, assimilated by plants in small 



quantities, 59. 



— bacterial production from nitrates, 



208. 



— harmful in larger amounts, 85. 

 Nitrobacter. See Nodule organism. 

 Nitrogen, determination of, 348. 



— evolution of gaseous, in decomposi- 



tion of organic matter, 191. 



— fixation of, 182, 195. See also 



Nitrogen fixation. 



— fixing power, 265. 



— gaseous, supposed assimilation by 



plants, 14. 



supposed evolution from soil, 



182. 



— in plant, association with calcium, 



74;. 



— nutrition, distinction between legu- 



minous and non - leguminous 

 plants, 18, 21, 24. 



— recuperative agencies in soil, 182. 



— source of, for vegetation, 10, 14 et 



seq., 18, 20. 



— content of soils; Broadbalk, 153, 



relation to loss on ignition, 



335- 



upper and lower limits, 



184. 



Wilderness, 183. 



grain, effect of length of 



ripening period, 54. 



— increased by magnesium 



oxide and car- 

 bonate, 75. 



sodium hydrate and 



carbonate, 73. 

 unaffected by many salts, 



73- 



— cycle in soils, 175, 178. 



— fixation, attempts to induce in soils, 



201. 



by electric discharge, 196. 



free - living organism s — 



Algae, 200, 255. 



— — Azotobacter, 197. 



Clostridium, ig6. 



fungi, 259. 



nodule organisms, 25, 204. 



other organisms, 200, 208. 



in soil, 182. 



estimated amount of, 207. 



— in soils, compounds present, 145. 

 loss of, 178, 181. 



26 



Organic compounds absorbed and util- 

 ised by plants, 57. 



decomposition in soil, 212. 



effect on plants, 248. 



— matter in soil, chemical properties 



of, 138 et seq. 

 colloidal properties of, 



130. 

 — decompositions, summary 



of, 214. 



determination of, 348. 



effects of, 130, 329. 



on fertility, 130, 



334- 

 on water supply, 



131, 132. 



partially decom- 

 posed, 130. 



undecom posed, 



130. 



fractionation of, 141. 



masks effects of clay and 



sand, 132. 



nature of, 129. 



original deposit, 129. 



recent formation, 129. 



