152 University of California Publications in Agricultural Sciences [Vol.3 



ages of calcium and magnesium accompany low growth ; low percent- 

 iles of calcium and magnesium go with much increased growth. No 

 iron could be quantitatively determined in cultures 8 and 9. The 

 copper content shows no variations which may be regarded as impor- 

 tant, in fact the amount taken up by the plants is somewhat lower 

 where decreased growth is shown. 



Zinc sulphate was used with copper sulphate as shown in table 20. 

 There is little evidence of antagonism between the two salts. At the 

 same time there is evidently no direct relationship between concen- 

 tration and toxic effect, since growth does not decrease regularly with 

 increasing concentration. While the percentages of calcium and mag- 

 nesium found are somewhat irregular, they increase rapidly as growth 

 becomes less. The percentage of magnesium found in the tops in 

 culture 8 was 1.10 per cent, and in the roots 1.91 per cent. This 

 occurred with the same concentration of the magnesium ion in the 

 nutrient as in culture 1. The percentage of copper found in the dry 

 matter is distinctly larger than that found in the preceding series, in 

 which copper sulphate alone was used. 



Copper sulphate used with ferric sulphate shows no evidence of 

 antagonism between the two if the growth of the tops alone is con- 

 sidered, but with the roots there is a marked increase in growth in 

 cultures 3 and 4 of the series. The percentages of magnesium found 

 in the roots is low and constant, which contrasts markedly with the 

 amounts determined in the previous series. The calcium likewise 

 varies but little in the tops and its percentage remains low. On the 

 other hand, the percentages of calcium in the tops and magnesium in 

 the roots show marked increases as growth decreases. The amount 

 of iron remains very uniform until the last culture of the series is 

 reached, when a marked increase is recorded. It will be noted that the 

 percentage of calcium decreases to nearly one-third of the original in 

 the same culture. This relation has been noted previously in other 

 series. 



The stimulation resulting from the addition of ferric sulphate to 

 the nutrient solution in the concentrations given in table 22 is remark- 

 able, a total dry weight of 3.9016 grams for the tops of six plants 

 being recorded. The growth of the roots does not parallel that of 

 the tops. In the highest concentration of ferric sulphate employed, 

 the root growth decreased while the growth of the tops was increased. 

 Attention has already been called to cases of this kind in which 

 there may be an increase in the growth of tops with a decrease in 



