SUBJECT INDEX 



399 



Humin, 141, 146, 



— hydrolysis of, 146. 



Humus, 133, 137, 303. See also Or- 

 ganic matter in soil. 



— analysis of, 138. 



— artificial production of, from dihyd- 



roxyfurfuraldehyde, 



143- 



quinone, 143. 



— sugar, 142. 



— colloidal properties, 140. 



— effect on iron compounds in soil, 



165. 



— formation in soils, from cellulose, 



141, 177. 



field observations, 136 et 



seq. 



— function in soil, 15, 130, 144. 



— not effective in denitrification, 209. 



— of field soils, 137. 



similarity to peat, 137. 



forest soils, 136. 



— relation to Azotobacter, 199. 



— soils, 94, 307. 



characteristics of plant growth 



on, 310. 



— soluble, supposed necessity for 



fertility, 143. 



— supposed food of plants, 7, 8, 12, 



15. 

 " Hungry " soils, 108, 312. 

 Hydrogen ion concentration of plant 

 juices, 81. 



soil solution, 116. 



in relation to plant growth, 



81. 

 Hydroxyl ion more toxic than hydrogen 



ion, 81. 

 Hygroscopic coefficient, 223. 



relation to other moisture co 



efficients, 226. 



— water, 166 ct seq. 

 Hymatomelanic acid, 141. 



Improvement of exhausted soils, 321. 



soil, methods of, 320. 



Injurious factors (to plants), effect of, 

 42, 80. 



— substances (to plants), 80. 

 Inoculation of soil with Azotobacter, 



203. 



nodule organisms, 208. 



Iodides and plant growth, beneficial in 



small quantities, 56, 76, 

 harmful in larger 



amounts, 76. 

 Ions, antagonism of, 79. 



— complex equilibrium in plant cell, 



79. 



Iron compounds in soil, 338. 

 part played in pan forma- 

 tion, 163. 



effect on plant growth, 75, 84. 



Irrigation, 50, 86. 



— and varying requirements of plants, 



50. 



— effect on soil organisms, 272. 



— injurious effects of excessive, 50. 

 Iso-electric point, i6r. 



Lamziekte, 318. 



Law of minimum, Liebig, 16. 



Mitscherlich, 28. 



Leaching, effect on soil, 99. 



Lead mines, damage done to vegetation 



by, 85. 

 Leguminous crops, effect on soil, 184, 

 208. 



nitrogen fixation, 24, 207. 



Liebig's patent manure, 16, 17. 

 Light and plant growth, 54. 



— indirect effect on soil, 55. 

 Lime as a sterilising agent, 273. 



— effect on soil, 11. See also Calcium 



carbonate. 

 organisms, 273. 



— indications of lack in soil, 336. 



— magnesia ratio, 75, 339. 



— requirement of soil, 114, 119. 



— determination of, 350. 



Limiting factors, 28, 38. 



Lithium salts, harmful to plant growth, 



73- 

 Loams, 315. 



— characteristics of plant growth on, 



315. 

 Lodging of cereal crops, 317. 

 Loess soils, 100. 

 Lysimeter experiments, 178, 180. 



Magma unguinosmn, the principle of 



vegetation, 4. 

 Magnesian limestone, effect as fertiliser, 



86. 

 Magnesium associated with formation 

 of oil in plants, 75. 



— carbonate, effect on soil organisms, 



273. 



— compounds in soil, 339. 



— in seed, 75. 



— salts, effect on plant growth, 75, 86. 

 supply of potassium salts, 



151. 

 Manganese salts, beneficial effect on 

 nodule organisms, 

 207. 

 plant growth, 56, 76. 



