396 University of California Publications in Agricultural Sciences [Vol. 1 



PAGE 



Reactions of copper with giowiug- points 450 



Varying resistance of individual cells to copper 454 



Diagnosis of copper injury 454 



Part II. — General Discussion 458 



Preliminary statement 458 



Accumulations of copper 458 



Possible effects upon health 460 



Amounts and significance of copper in aerial vegetation 461 



Amounts and significance of copper in root systems -.- 46i5 



Relations between amounts of copper in root systems and in- 

 jury to plants 466 



Pathological effects 467 



Soil conditions relating to toxic effects of copper upon plants .... 468 



Stimulation 470 



Field observations 472 



Effects of river sediments 473 



Effect of cultivation upon alfalfa 474 



Summary 478 



Part III. — Appendix 480 



Methods of analysis 480 



Reagents and apparatus 480 



Manipulation 480 



The determination of copper in small amounts of plant ashes 483 



Bibliography 487 



Part I.- EXPERIMENTAL WORK 



INTRODUCTION 



The region to which the studies described in this publication 

 more particular!}^ relate lies in southeastern Arizona in Greenlee 

 and Graham counties and consists, first, of the Clifton-]\Iorenci 

 mining district and second, of the irrigated lands along the Gila 

 River from twenty-five to sixty miles below. The Clifton-IMorenci 

 mining district is drained by Chase Creek into the San Francisco 

 River, which in turn empties into the Gila. From the Gila, be- 

 ginning at a point about twenty-five miles by channel below 

 Clifton, irrigating waters are withdrawn for the use of the rich 

 lands extending somewhat discontinuously from above San Jose 

 to Fort Thomas, a distance of thirty miles. For about forty 

 years, this up-stream mining district and the irrigated lands 

 below have developed together from small beginnings into large 

 industries. 



Beginning with the initiation of smelting operations on the 



