580 INDEX. 



PAGR 



Physical and chemical causes of vegetative features 505 



conditions of plant growth 319 



Physical analyses, correlation with popular names 96 



results of 94 



table. Mississippi and California soils 98 



analysis of soils 88 



constituents of soils 10 



Physico-chemical investigation of soils 313 



Physiological soil analysis 333 



Phosphate fertilizers, importance of 65 



Phosphate fertilization, in arid region 393 



in California 393 



Phosphoric acid, limits of adequacy in soils 355 



minute amounts leached from soils 24 



no constant difference between arid and humid soils. . 393 



rendered inert by ferric hydrate 355 



Phosphorites, low-grade, of Nevada, Russia 63, 64 



Plane tree, oriental, resistant to alkali 480 



Plant-adaptation " varying from province to province " 523 



Plant associations, plant formations 315 



Plant distribution, Thurman's physical theory of 519 



Plant-development under different temperatures 309 



Plant-food, accumulation in finest parts of soils 87 



high percentages mean high land value 346 



ingredients, condition of, in soils 319 



in virgin soils, lowest limit of, table 35 2 



limits of adequacy 353 



minute amounts may produce large crops 4 10 



percentages, what are high 34$ 



percentages, low 346 



water-soluble, reserve, unavailable 3 2 



Plant-growth on arid subsoils 166 



Plants, deep-rooting in arid region i?4 



indicating irreclaimable alkali lands 535. 53^ 



Plant root action, cannot be imitated in laboratory 3 2 4 



Plasticity, absence of, in fine powders 60 



of clay, causes of 60 



lost by burning 60 



Plot tests, difficulties and uncertainties of 334 



plan of, figure 335 



Plowsole, how formed, by shallow irrigation 186, 241 



Poor chalk lands 5 2 5 



Pore-space IQ 8 



Porosity of humus 1 2 4 



Port Hudson bluff, lignite in, figure I2 $ 



recession of i J 6 



Potash, abundant in arid soils 395 



and soda in arid and humid region 394 



