Permeability 141 
same osmotic concentration, but from a mixture of the two having 
the same total osmotic concentration (0-15 KC 1 + 0-048 M LiCl), salt 
enters a little faster than from the pure lithium chloride solution 
(0*192 M) but much slower than from the pure potassium chloride 
solution (0-200 M). 
The same rule was found to hold for anions. The action of any 
salt in furthering or retarding intake was found to be the sum of the 
action of its two ions. 
While it is clear from earlier considerations put forward in this 
chapter dealing with the unequal absorption of ions, that the plasmo- 
lytic test is not free from objection, direct evidence that antagonistic 
action is due to mutual hindrance to intake is forthcoming from 
chemical analysis of tissues and -colorimetric determinations in cells 
and external solutions. By such means it has been shown by Sziics 
(1911, 1912) that roots of Cucurbita Pepo rapidly absorb enough 
copper from pure solutions of copper sulphate not only to inhibit 
the response of the hypocotyl and root to gravity and light, but also 
to give a very definite qualitative test for copper. If aluminium 
chloride is added to the solution of copper sulphate, the inhibition 
of the geo tropic and phototropic reaction is delayed and the copper 
is absorbed to a much less extent in the same time. The maximum 
depoisoning effect is produced with a ratio of 0*15 N aluminium 
chloride to 0*025 N copper sulphate. 
From water culture experiments with Eriophorum vaginatum , 
Phragmites communis and Carex riparia, Stoklasa, Sebor, Tymich 
and Cwacha (1922) conclude that they find antagonism between 
aluminium and ferric ions. These plants were maintained with their 
roots in complete nutrient solutions which in some cases contained 
in addition aluminium nitrate, in others ferric nitrate and in yet 
others both these salts. By analysis of the experimental solutions 
after the lapse of 13 days it was found that less iron and aluminium 
were absorbed from the solution containing both these salts than 
from those containing only one, although the conditions were other¬ 
wise equal and the concentration of both the aluminium nitrate and 
the ferric nitrate was the same, namely 0*002 N, as in the solutions 
containing only one of these salts. Thus, in the experiments with 
Phragmites communis the quantity of aluminium absorbed from the 
solution containing this without iron was 51*3 mgm., the quantity 
of iron absorbed from the solution containing this without aluminium 
was 46*6 mgm. while from the solution containing both, 27*3 mgm. 
aluminium and 8*4 mgm. iron were absorbed. 
