ILLUSTRATIONS 

 PLATES 



PAGE 



Plate I. — Corn root tips killed in a solution of 1 part copper to 100,000 

 of water, and colored by (1) caustic potash, violet; (2) hydrogen 

 sulphide, brown; (3) potassium xanthate, yellow; and (4) potas- 

 sium ferrocyanide, red Frontispiece 



Plate II. — Eoot system of corn plant injured by .1 per cent of copjier 



in the soil, with normal corn root system for comparison 204 



Plate III.— Individual roots of corn injured by .1 per cent of copper 



in the soil ; with normal roots for comparison 204 



Plate IV. — Thickened rootlets and proliferated root tips of corn in- 

 jured by .1 per cent of copper in the soil ; with normal rootlets and 

 root tips for comparison 204 



FIGURES 



Fig. 1. — General map of Clifton, Morenci, and Gila River District, 

 Arizona 147 



Fig. 2. — Detail map of the Gila River irrigation district, Graham 

 County, Arizona 154 



Fig. 3. — Corn cultures gi'o'wn in University of Arizona well water, 

 containing .03 to 3. parts per million of copper as basic carbonate .... 166 



Fig. 4. — Bean cultures showing effects of varying concentrations of 

 copper in distilled water and in solutions of mixed salts 169 



Fig. 5. — Diagram of pot culture irrigated through 2-inch pot.— 177 



Fig. 6. — Wheat and barley irrigated with copper solutions filtered 

 through soil, and ■^^•ith well water 180 



Fig. 1 .■ — Bean cultures grown in soils containing .0 to 1.5 per cent 

 copper as precipitated carbonate 182 



Fig. 8. — Corn cultures grown in soils containing .0 to .2 per cent cop- 

 per as precipitated carbonate 182 



Fig. 9. — Corn cultures grown in soils containing from .01 to 1 per cent 

 copper as sulphide 183 



Fig. 10. — Corn cultures growTi in soils containing .0 to 1. per cent cop- 

 per as silicate 185 



Fig. 11. — ;Pot cultures of corn in field soils containing tailings 186 



Fig. 12. — Showing effects of copper influenced by tilth of soil 187 



Fig. 13. — Photomicrograph of root tip of corn grown in water culture 



and poisoned by 1:200,000 of copper in solution 202 



Fig. 14. — Tangential longitudinal section of corn root groAvn in soil 

 containing .1 per cent of copper as copper sulphate. (X 300 diam.) 204 



Fig. 15. — Diagram showing root systems under influence of tailings 

 blanket 222 



Fig. 16. — Diagram showing yields of alfalfa from head to foot of a 

 land damaged by tailings in 1905; and the same land in 1916 after 

 disc harrowing annually 226 



