258 Walter Stiles and Ingvar Jorgensen. 
the chlorides but obtained analogous results with nitrates. In each 
case he found the toxicity of a mixture of the two salts was less 
than that of either salt singly, the concentration ((H2M) being 
constant throughout the experiments. In each case there is a 
definite ratio of the two constituents of the solution which gives a 
maximum growth. Above and below this ratio there is a falling 
off which is greater the further removed the ratio is from the 
optimum. Similar results were obtained in soil experiments. 
Osterhout concludes from these researches that sodium is not 
useless but has a protective effect on plants, a question to which he 
returns in a later paper (30). He conceives “normal life as possible 
only when the necessary salts combine with the colloids of the 
living substance in a definite ratio.” This ratio it is supposed will 
be dependent upon the composition of the solution outside the 
plant according to the law of mass-action. He emphasises the fact 
that antagonism does not depend merely upon an action between 
the salts themselves, but upon their action on the living substance. 
In his next experiments Osterhout demonstrates antagonism 
by means of plasmolysis (28). Having previously shown (25) that 
the contraction produced by a salt solution may not be true 
plasmolysis at all but a contraction resembling it, due to the 
toxic effect of the salt itself entering, the necessity of care 
in distinguishing true plasmolysis is emphasised. He finds that 
Spirogyra plasmolysed in ’2M CaCl 2 but not in ‘195M CaCl a 
„ „ „ -38M NaCl „ „ „ *375M NaCI. 
It is, however, promptly and very markedly plasmolysed in a solution 
of lOOcc *375M NaCl + lOOcc *195M CaCl 2 showing, therefore, 
the non-entrance into the cell-sap of the salt in the case of a 
mixture of these chlorides, while in the case of single salts of the 
same concentration the salt diffuses through the plasma-membrane 
as well as the water, and so no plasmolysis is produced. 
The most ingenious of Osterhout’s methods for demonstrating 
antagonism is undoubtedly that in which he uses the difference in 
electrical resistance of living and dead tissue to determine the rate 
at which single salts or mixtures of salts kill Laminaria (29). 
Discs of the flattened laminae of this alga were cut out by means of 
a cork-borer, and from 100 to 200 of them packed closely together 
to form a compact cylinder of tissue. At each end of the cylinder 
was a platinum electrode. The resistance of the whole cylinder of 
discs was then measured by means of Kohlrausch’s method. The 
resistance of the cylinder of living tissue in sea water was found 
