Absorption of Salts by Plants. 259 
to be 1110 ohms, when dead in a solution of the same electrical 
conductivity as sea water, the resistance was only 320 ohms. The 
extra resistance can only be due to the resistance to the passage 
of the ions by the plasma-membranes of the living cells, this extra 
resistance disappearing when the cells are dead and the membranes 
become completely permeable. 
By this method it was shown that calcium chloride was much 
less toxic than sodium chloride, but that a mixture of the two in 
the proportion of lOOOcc M.NaCl to 15ccs. M.CaCl 2 diluted till its 
conductivity equalled that of sea water retained its original resistance 
for 24 hours. This can only be ascribed to the cell membranes 
retaining their property of impermeability to the two combined 
ions, so that here we have a demonstration of antagonism by a 
most original and striking method. 
The earlier observations of Osterhout have been extended by 
Hansteen (10), who in a somewhat lengthy paper gives the results 
of experiments on the antagonism between potassium and other 
metallic ions. He worked with a wide range of concentrations, 
the solutions being as a rule much dilutee than those of Osterhout. 
He used nitrates as a rule, but occasionally other salts. 
His method consisted in growing seedlings of a Norwegian 
variety of Wheat for 14 days. His first experiments were made 
with solutions of single salts to determine the specific effect of 
each metallic ion on root development. Later he used mixtures 
of potassium nitrate and the antagonising salt. In any series the 
concentration of any solution was constant, but the ratio of K to 
the antagonistic kation varied. The cultures were done in duplicate. 
The toxicity was determined by means of measuring the dry 
weight of the roots produced. Observations were also made on 
the appearance of the roots. 
As a result of these experiments Hansteen records a definite 
antagonism between potassium and calcium, and between potassium 
and magnesium (though it is not very great); between potassium 
and sodium he found a little, though scarcely noticeable, antagonism. 
His results differ in many details from those of Osterhout’s. 
Thus in the case of potassium and magnesium he found the optimum 
M M 
ratio was given by the mixture 100 jqq KNO a + 4-0625 jqq 
Mg(N0 3 ) 2 , whereas Osterhout finds the best mixture with chlorides 
to be 100 0-0375M KC1 + 25 0-0375M MgCl 2 , a very different ratio; 
but of course the concentrations and the anions are different in the 
experiments of the two observers. 
