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



TABLE XXIV 

 Wheat Grown in Garden Plots Containing Cu as CuSOi (1914) 



TABLE XXV 

 Wheat Grown in Pots to Check Plots Containing Cu as CuSOi (1914) 



Sample Cu added. 

 No. per cent 



5672o .0025 



Condition 

 of leaves 

 o7 in high 



Green; 'Ii m 

 Toxic effects begin at about .005% Cu in soil. 



5673o 

 5674a 



5675a 



5676« 



.01 

 .025 



.05 



.10 



Yellowish; 23 in. high 

 Yellow and stunted; 17 



in. high 

 Yellow and stunted; 12 



in. high 

 Yellow and stunted; 4-12 



in. high 



The corn series contains much smaller proportions of copper 

 in the roots than either of the wheat series, a fact explained in 

 part by the coarser roots of corn, which therefore have less ab- 

 sorptive surface in proportion to their weight. Wheat roots 

 grown in plots show much more copper than pot samples, 

 although the copper is much more toxic to the plants in pots 

 than in plots, a contradiction not easily understood unless it 

 be that other less favorable conditions of growth in pots were 

 responsible for the backward condition of the plants. 



Field Samples of Soils axd Vegetatiox 



In order to relate, if possible, the experimental work detailed 

 on previous pages to samples of field material, roots of barley, 

 wheat, oats and corn, were collected in the district studied and 

 the amounts of copper in them determined. The samples of bar- 



