LIST OF ILLUSTRATIONS 



Jethro Tull 



Frontispiece 



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Utah sagebrush land .... 



Native sod of Rocky Mountain foothills 



New Mexico dry-farm lands . 



Land above the canal .... 



Weighing pots in transpiration experiments 



Plant house for transpiration experiments 



The quantity of water required for the production of dry 



matter 



The rolling hills of the I'alouse wheat di.strict 

 Rainfall chart for the United States 

 Sagebrush under ten inches rainfall 

 Sagebrush under fifteen inches rainfall . 



Rainfall chart for the world 



Physical features of the dry-farm territory of the 1 



States 



Chart showing the distribution of rainfall in the w 



United States ....... 



Sagebrush land covered with snow 

 Sunshine in Canada and the United States . 



Soil structure . 



Difference between humid and arid soils 

 Deep soil, .suitable for dry-farming 

 Gravelly soil, not adapted for dry-farm 

 Soil augers 

 Wheat roots . 



Alfalfa roots . 



Sugar-beet roots 



Corn roots 



Root systems under humid and arid conditions 



nited 



estern 



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