582 INDEX. 



PAGE 



Regur soils, Deccan, India 414 



formation of 415 



" guvarayi ' ' hardpan 415 



present production 414 



Reh of India 440 



Reserve plant-food in soils 320 



of zeolites, carbonates, phosphates 321 



Residual soils 11,13, 22 



Rhizobia, adaptation to symbiosis 154 



inoculation of soils with , 154 



increase of crops by inoculation with 155 



of legumes 150 



mode of infection 154 



varieties of forms 154 



Rhubarb, sensitive to alkali 475 



Rhyolites, soils from 53 



River bars, formation of 7 



Rivers, amount of dissolved matters carried by 24 



flood-plains of 13, 14 



sediment carried by 24 



waters, analyses of, table, discussion 23, 24 



white and green 4 



Rock crystal 29 



Rocks as soil-formers 47 



chemical decomposition of 16 



cleavage of 3 



definition of xxix 



disintegration of, under extremes of temperature 2 



effects of heat and cold on I 



erosion of by sand 10 



forming minerals 29 



fragments, rounding of, by flowing water 6 



Rock powder 85 



Rock-weathering in arid and humid climates 47 



Rohhumus 122 



Rolling of soils, of influence of, on heat 305 



Root action, limitation of 351 



Root bacillus, figure 149, 150 



Root crops, effects of alkali upon 474 



"Root development in the arid and humid regions 169 to 176 



Rooting, deep, from proper irrigation 243, 245 



Roots, chemical action of 21 



force exerted by 19 



secrete carbonic acid 20 



Root system in the- humid region ; figure 168 



Rotten Limestone, soils from, analyses 54 



Runoff of rain water. . , 216 



