1917] Lipman-Gericke : Smelter Wastes and Barley Growth 531 



blance between the behavior of MnSO^ and MnCL in the first 

 crop is limited in extent, MnCla resembles MnSO^ much more 

 in its effects on barley growth in the first crop than it does any 

 of the other salts under similar circumstances. Again, we are 

 obliged to stop with this general comparison owing to the high 

 concentrations of MnCL employed, as compared with the rela- 

 tively much lower or much higher concentrations of the other 

 salts employed. 



Second Crop 



When the total dry matter is considered (see table X&), the 

 second crop of the MnCl, series gives the latter salt a reversal 

 of form. At the first three concentrations at which it notably 

 stimulated the production of dry matter in tlie first crop, it 

 becomes decidedly toxic in the second crop. On the other hand, 

 at the concentrations above 1500 p. p. m., at which it was acutely 

 toxic in the first crop, MnCL is stimulating when the total 

 yields of the treated as against those of the untreated pots are 

 considered. Such marked reversal of effects of MnCl, between 

 two succeeding crops on the same soil needs further attention 

 under the general discussion below. Following the procedure 

 employed in the case of the other series, we may now study sep- 

 arately the yields of straw, grain, and roots as given in table 

 X&. Taking the straw yields first, we find that they were, in 

 all cases but one or possibly two in the series, much larger than 

 those of the control pots, and that at concentrations in excess 

 of 1500 p. p. m. the average yield of straw was nearly twice as 

 great as that of the control pots. While different in degree, 

 therefore, this effect of MnCL in the second crop is very similar 

 in kind to that exerted by MnSO^ in the second crop with 

 respect to the yield of straw. 



In the case of the grain, however, we find totally different 

 conditions, for here only one case of stimulation is noted and 

 that, owing to the great discrepancy in the duplicates, is an 

 unsafe one to accept. In excess of 3000 p. p. m., MnCL mani- 

 fests a very marked toxicity so far as grain production is 

 concerned, until at 6000 p. p. m. very little or no grain is pro- 

 duced. This result is again different only in degree, not in 



