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C. B. LIPMAN AND W. F. GERICKE 
powers of copper and zinc ions to the toxic properties of other ions 
have been few and the results obtained rather fragmentary. They 
have dealt chiefly with animal material, indirectly, however, a small 
amount of data has been obtained in experiments with plant or fungus 
organisms as regards antagonistic powers of copper and zinc. We 
use the term indirectly advisedly, since, unlike our experiments, those 
in question have attempted to antagonize the toxic properties of copper 
and zinc by adding the less toxic or non-toxic metals to a given medium 
for the growth of the organism tested, whereas we have attempted to 
use copper and zinc to antagonize the toxic concentrations of what are 
known as "alkali" salts in soils. The indirect evidence is very impor- 
tant, however, and deserves mention here. Clark^ was able to dirninish 
markedly the toxic effects of CUSO4 and CuCU for germination of 
spores of Oedocephalum albidum and Rhizopus nigricans by the addition 
of various ammonium, sodium, and potassium salts. Among other 
heavy metals, Le Renard^ found that copper and zinc could be rendered 
much less toxic in culture media for Penicillium by the addition of 
various salts of ammonium, potassium and magnesium. True and 
Gies^ demonstrated that the toxicity of copper and zinc, as well as that 
of mercury in various salts for Lupinus albus, could be considerably 
reduced by the addition of calcium to the medium of growth. Sziics,^ 
working with Cucurbita pepo and using the responsiveness of the root 
to a geotropic stimulus as a criterion, found that AICI3 in certain 
concentrations possessed the property of inhibiting the toxic effects of 
CUSO4. More recently, Hawkins^ has shown to exist certain cases of 
undoubted inhibition of the toxic effects, on fungus spores, of heavy 
metals, including copper and zinc, by the presence of calcium, mag- 
nesium, or potassium nitrates. It will be noted that only two experi- 
ments with higher plants are cited among the investigations just 
reviewed. Moreover, Sziics used a very unusual and less convincing 
criterion for antagonism effects, and True and Gies used calcium to 
antagonize copper, but did not try the antagonistic properties of copper 
against the alkali or alkali earth metals or their ions. 
On the other hand, Lillie^ found that copper, as well as several 
4 Clark, J. F. Bot. Gaz. 33: 26-48. 1902. 
^Le Renard, Alf. Ann. Sci. Nat. Bot. IX. 16: 276-336. 1912. 
^ True & Gies, Bull. Torrey Club 30: 390-402. 1903. 
^ Sziics, Jos. Jahrb. Wiss. Bot. 52: 85-143. 1912. 
^Hawkins, L. A. Physiol. Res. i: 57-92. 1913. 
9 Lillie, R. S. Amer. Journ. Physiol. 10: 419. 1904. 
