IN MIxED SOLUTIONS 401 
In the mixtures of copper and calcium employed in our experi- 
ments, we may have had concentrations of each salt in different 
phases of action due to the degree of concentration. In CuCl, 
m/65536, we see that the Cu concentration is in the phase hinder- 
ing growth, the resulting elongation of the root being about 3 mm. 
When CaCl,, 7/128, was tested, it was found to be ina concentration 
markedly stimulating when referred to the control in water, grow- 
ing 20 mm. in the former case, against 14.5 mm. in the check, 
These opposite tendencies were brought together in the mixed solu- 
tion with the result that the concentration (in terms of the copper 
salt permitting the growth-rate seen in the simple copper solution) 
moved up to approximately four times that observed in the 
simple copper solution. The stimulating action of the calcium 
seems to have operated against the retarding action of the copper, 
and the result is a marked diminution in the poisonous action of 
the copper. 
The opposite result is seen in the mixture containing CuCl, 
and NaC]. The latter is in its growth-retarding phase until more 
dilute than m/128. Hence at w/16 it is in its growth-retarding 
phase, and when added to CuCl, at 7/65536, likewise in this 
phase, the result is a sum of toxicity and an increased depression 
of growth-rate follows the combined action of the two. This also 
applies to the mixtures containing magnesium. 
In considering the more complex mixtures of salts, indicated 
in Table VI, the chemical nature and influences of the resulting 
solutions are not readily determined. Much more concentrated 
solutions result in such mixtures with consequent decrease in dis- 
sociation. The probability that we are dealing with various kinds 
of non-ionized molecules, as well as with an indefinite number of 
ions, makes it impossible to speak definitely with confidence of the 
significance of our results in this connection. In general one may 
say that here, as in sea water, another complicated mixture of 
molecules and ions, the entrance of the calcium salt into the mix- 
ture is the stage in the synthesis at which the growth-rate ap- 
proaches that seen in the check, and the final addition of the 
potassium salt seems further to increase the growth-rate. Or, in 
other words, all the salt solutions except the calcium entered the 
mixture in a concentration at which singly they would cause a 
