1917] Lipman-Gericke : Smelter Wastes and Barley Growth 561 



regard to root yields. Smaller concentrations than those men- 

 tioned slightly depress straw and root production, hut definitely 

 stimulate grain production. 



6. In the greenhouse soil in the PbS04 series, first crop, the 

 straw production is depressed by about one-third the total 

 amount produced in the control. The depression appears to 

 be uniform at concentrations of from 200 p. p. m. to 1500 p. p. m. 

 PbSO^. Likewise, the root yields are depressed by even a 

 greater figure (about 60 per cent), and again almost uniformly 

 throughout. 



In the second crop the straw production is nowhere depressed 

 in the entire series and is stimulated at concentrations of from 

 300 p. p. m. to 600 p. p. m. PbSO^ as well as at scattering con- 

 centrations in excess. Root production, on the other hand, is 

 slightlj^ depressed throughout. 



In the third crop the straw production is markedly stimu- 

 lated at concentrations varying from 1000 p. p. m. to 2400 

 p. p. m. PbSO^, but slightly depressed at lower concentrations. 

 Grain production is similarly affected, and the PbSO^ remains 

 without effect on the roots within the same limits of concen- 

 tration. 



7. In the greenhouse soil in the potash alum series the first 

 crop shows stimulation to straw yields at all concentrations 

 varying from applications of 300 pounds to 2000 pounds KjO 

 per acre. Root yields are stimulated at the lowest concentration 

 named, but scarcely at all in the others. 



In the second crop the straw yields are again stimulated by 

 the doubling of the potash alum application throughout the 

 series. Relatively the stimulation is much greater than in the 

 first crop. Grain production and root production are also mark- 

 edly stimulated, the former at the smaller applications of potash 

 alum and in other isolated instances, and the latter throughout. 



In the third crop the straw yield is markedly depressed 

 throughout. The grain yields are slightly stimulated in some 

 cases, and in the balance remain unaffected. The root yields are 

 depressed similarly to the straw yields. 



8. In the greenhouse soil in the MnSO^ series the first crop 

 is stimulated in regard to straw yields at all concentrations be- 



