390 
R. P. HIBBARD 
The two views, namely, that the distilled water Is toxic per se, 
or that it is toxic because of the presence of poisonous substances 
in it, have been the principal ones held to the almost complete ex- 
clusion of any other. In this paper the writer wishes to draw attention 
to two other aspects of the distilled water problem. It seems that 
the problem is more a dynamic one than otherwise and in all proba- 
bility more than one factor enters into the explanation of why seed- 
lings cannot survive in distilled water. Right at this point it must 
be said that certain seedlings because of various physiological charac- 
teristics are less susceptible to distilled water injury than others. 
It is very probable that different varieties of seedlings and even 
different individuals of the same variety react differently to the same 
external conditions. From the work done in this laboratory but not 
reported the conclusion can be drawn that, providing one selects 
disease-free seed uniform in size, color^ etc., one can detect as much 
individual variation in the behavior towards toxic substances in solu- 
tion of seedlings of pure line seeds from one plant as in that of seed- 
lings of a mixed progeny from unknown source. It follows from this 
that a medium which affords optimum conditions for one organism will 
not be the best for another. A normal physiological solution as men- 
tioned above will perhaps afford optimum conditions for one kind of 
seedlings but not for another. Certain other salts or other proportions 
are better. In all probability there is no universal physiologically 
balanced solution. Loeb^ states that salt water is a physiologically 
balanced salt solution for such organisms as thrive in it and the blood 
of normal, healthy subjects can also be considered a physiologically 
balanced solution. From our knowledge of balanced solutions it 
may be assumed that the role of the various salts is one of antagonistic 
action, a neutralization of the toxic effect of a single salt or of the 
harmful proportion of the various salts in the medium. That distilled 
water cultures of seedlings are not physiologically balanced solutions, 
can be assumed without much danger of contradiction. Wherein, 
then, lies the inappropriateness of distilled water for control cultures; 
and wherein lies the explanation of the injurious effect of such waters, 
and still further injury as the seedlings continue to grow in it? This 
preliminary paper will endeavor to show, first, that the adjustment of 
^Loeb, J. The Relative Toxicity of Distilled Water, Sugar Solutions and 
Solutions of Various Constituents of the Sea Water for Marine Animals. Univ. 
Calif. Publ. i: 62 and 69. 1903. 
