1917] Lipman-GericJce : Smelter Wastes and Barley Growth 507 



yield of the latter, and in several other cases such increases 

 amounted to 30 per cent or 35 per cent. 



Giving brief consideration now to the yields of roots alone, 

 we find tliat they, too, like the total dry matter in general, are 

 definitely affected by the CUSO4 treatment. Increased root pro- 

 duction over that in the control pots is found in all the pots 

 having concentrations from 50 p. p. m. to 600 p. p. m. CUSO4, 

 inclusive. Bej^ond that point, however, unlike the case of the 

 total dr}^ matter considered, the increased concentrations of 

 CUSO4 appear to depress root development very definitely. The 

 decreases continue steadily more significant as the concentration 

 of CuSO^ increases from 600 p. p. m. to 1100 p. p. m., when the 

 toxic effect seems to reach a stationary point and no further 

 decreases occur, even though more CUSO4 is added up to 

 concentrations of 1500 p. p. m. 



Taking into consideration the effects of CuSO^ on the first 

 crop of barley in the greenhouse soil in regard to both tops and 

 roots produced, it appears that we must consider the point of 

 stimulation to cease at 600 p. p. m. CUSO4. It is possible in 

 addition that even the 700 and 800 p. p. m. concentrations may 

 be looked upon as still stimulating to both tops and roots of 

 the barley plant in the soil in question. Beyond those points, 

 however, CUSO4 is stimulating, in the first crop, to the produc- 

 tion of tops onl}', not to the production of roots. 



Second Crop 

 The very large decrease in yield of the second crop in the 

 same pots, so far as total dry matter is concerned, is clearly 

 indicated in table lib. This is evidently not due to the doubling 

 of the percentage of CUSO4 in pots receiving treatment, since 

 the decrease in the second as compared with the first crop is 

 just as clearly marked in the control pots. On the other hand, 

 whereas the first crop produced practically no grain, probably 

 for reasons above discussed, the second crop produced a large 

 yield of grain, amounting not infrequently to 25 per cent or 

 considerably more of the total dry matter. Again, we see in 

 the figures for the second crop the disparity between yields of 

 duplicates, but again also the consistently large yields of dry 



