XU CONTENTS 



PAGE 



Temperature 42 



Relative Humidity 45 



Sunshine ........... 46 



"Winds 47 



Summary of Features 48 



Drouth 49 



CHAPTER V 



Dry-farm Soils 50-80 



The Formation of Soils 51 



Physical Agencies 



Chemical Agencies 

 Characteristics of Arid Soils 56 



Clay 



Sand 



Humus 



Soil and Subsoil 



Hardpan 



Leaching 



Alkali Soils 



Plant-food Content 



Summary of Characteristics 

 Soil Divisions ......... 74 



Great Plains District 



Columbia River District 



Great Basin District 



Colorado River District 



California District 

 The Judging of Soils 78 



CHAPTER VI 



The Root-systems of Plants ...... 81-93 



Functions of Roots 81 



Kinds of Roots g2 



