COPPER AND ZINC AS ANTAGONISTIC TO ALKALI " SALTS 1 53 
other toxic metals, possesses definite powers of antagonizing the toxic 
effects of NaCl on the normal existence and activation of cilia in the 
larvae of a marine annelid (Arenicola). With the exception of uranium, 
however, copper was the most feeble antagonistic agent to the action 
of NaCl just mentioned of thirteen metals tested. 
In view of the negative results obtained with copper by Loeb, and 
the entire lack of data, in so far as the more important functions of 
plants are concerned, on the antagonistic action of that metal to the 
alkalies, we deemed it wise, among the different series of antagonism 
experiments carried out in our laboratory, to test the action of copper 
as an antagonistic agent to "alkali" salts in soils. This seemed par- 
ticularly important in view of certain marked stimulating effects 
obtained by us^^ through the presence in the soil of copper, zinc and 
other metals, in the growth of barley in soil cultures. Owing to many 
similarities between the stimulating effects of copper and zinc in the 
studies just referred to, we decided to study the antagonistic powers 
of zinc, as well as those of copper, in the new experiments. The latter 
have now been completed and the results have, in many ways, been 
so striking as to justify their publication at this time. Our data con- 
stitute the first evidence, so far as we are aware, of the antagonistic 
action of copper and zinc to the toxic effects of ''alkali " salts as regards 
the living cells of higher plants. 
Methods Employed in the Experiment 
The plants used as indicators of the salt effects here studied were a 
selected strain of the Beldi variety of barley (Hordeum vulgare). 
They were grown in soil in 8-inch earthenware pots which were paraf- 
fined prior to the introduction of the soil. Twenty seeds were planted 
in every pot and the plants were later thinned to six plants per pot. 
As nearly as possible, optimum and uniform moisture conditions were 
maintained in all the soils. Some of the common salts of alkali soils, 
viz, NaCl, Na2S04, and Na2C04, were employed as toxic agents and 
were added on a percentage basis of the dry weight of the soils. The 
antagonistic agents were CUSO4, ZnS04, CuCl2, ZnCU and CuCOs, and 
were added to the salt-treated soils on the basis of parts per million of 
loLipman and Gericke, Univ. Cal. Publ. Agr. Sci, i: 495-587. 
1^ Hibbard, R. P., has shown that CUSO4 and chloral hydrate antagonize each 
other, but such an instance of antagonism is not comparable with those which we 
furnish in this paper since chloral hydrate is an organic compound. 
