1917] Lipman-Gericlce : Smelter Wastes and Barley Growth 535 



Opposed to the findings of the investigators just named 

 were those which showed evidence of stimulating effects of cop- 

 per salts to plants in solution cultures. Among these investi- 

 gators were Tschirch,"- Montemartini,-^ and Forbes.^* So far 

 as germination of seeds is concerned, Effront^'^ also noted the 

 stimulating effect of copper. Owing to conflicts in the results 

 obtained by different investigators working with copper in solu- 

 tion cultures, one seems scarcely justified in subscribing to the 

 statement above quoted from Brenchley, even if it were made 

 to apply only to solution cultures. As Dr. Brenchley herself 

 admits, there is no absolutely satisfactory method for determin- 

 ing whether or not a certain substance is toxic or stimulating 

 to plants. But from the theoretical standpoint of ascertain- 

 ing how the protoplasm of the plant is affected by a given 

 substance, if at all, the solution-culture method is the only one 

 involved, since the other methods are confessedly not intended 

 to show anything more than effects of substances on plants under 

 conditions closely approximating the natural. If, then, the 

 solution culture method is the only one among those at present 

 known that is suitable for studjdng the effects of different chem- 

 icals on plant growth in a more or less intimate way, why do we 

 obtain the conflicting results above noted with respect to the 

 effects of copper on plants ? The answer to this question is to be 

 found in a number of circumstances surrounding the manipula- 

 tion of the solution-culture method. Some investigators use 

 distilled water, others use tap water, still others physiologically 

 balanced solutions of a large variety. For reasons well known 

 to plant physiologists, the results of such different media among 

 the solution cultures must show wide discrepancies. If, however, 

 the claim is made that all media but pure distilled water be 

 discarded in such work, owing to the factors of salt antagonisms 

 which enter into salt solutions to vitiate results, a very strong 

 counter-claim can be made. The protoplasm of plant cells is not 

 in a natural medium when it is placed in distilled water, and 



22 Abstract in Chem. Ztg., 18, p. 320; E. S. R., 6, p. 872. 



23 Staz. Sper. Agr. Ital., 44, p. 564. 



24 Results soon to be published, Univ. Calif. Publ. Agri. Sci. 



25 Compt. Rend. Acad. Sci. (Paris), 141, p. 626; E. S. R., 18, p. 126. 



