CONTENTS 



CHAPTER PAGE 



I. Introductory 3 



II. Geographical Distribution 6 



North America. Canada. United States. Mexico. South 

 America. Africa. Egypt. Europe. Asia. India. Australia. 



III. The Origin of Alkali 16 



Composition of Soil-forming Materials. Salts from Ancient 

 Seas. Jurassic Beds, Montana. Arms of the Ocean. Evapora- 

 tion of Saline Lakes. Formation of Soluble Carbonates. 

 Nitrate Formation. Concentration by Irrigation Water. Rela- 

 tion of Origin to Methods of Treatment. 



IV. Nature of Alkali Injury to the Plant 34 



Prevention of Water Absorption. Effects on Germination. 

 Effect on Structure of the Plant. Injury at the Surface of the 

 SoU. 



V. Toxic Limits of Alkali 4 2 



Toxicity in Solution. Nutrient Solutions. Alkali Solutions. 

 Seed Germination. Seedling Transference into Alkaline Solu- 

 tions. Soil Results: in Sand, in Loam Soil. 



VI. Native Vegetation as an Indicator of Alkali 60 



How Plants Indicate the Soil. Alkali-indicating Plants: Well- 

 defined Alkali-indicating Plants, Alkali-indicating Plants not 

 Commonly Forming the Major Portion of Alkali-land Vegeta- 

 tion. Discussion of Plants: Inkweed or Salt-wort, Tussock 

 Grass {Sporobolus airoides), Kern Greasewood or Bushy Sam- 

 phire (Allenrolfea occidentalis), Dwarf Samphire (Salicornia 

 subterminalis), Greasewood (Sarcobatus vermiculatus), Alkali- 

 heath (Frankenia grandfolia campenslris), Cressa (Cressa 

 cretica truxillensis), Salt-bush or Shadscale (Atriplex spp.), 

 Kochia or White Sage (Kochia vestita), Salt-grass (Distichlis 

 spicata), Other Plants. Description of Alkali-indicating Plants. 



xi 



