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AMERICAN JOURNAL OF BOTANY 
[Vol. 8, 
may be explained on the basis of its small molecular concentration (0.13 
M). If all these salts were of the same molecular strength, they would 
doubtless be found to fall into four groups depending on their valency. 
The sodium dichromate forms an exception because of its acidity. The 
acidity is slightly higher than the limit which was shown by Osterhout (2) 
to be without effect on permeability, with the result that there is a very 
small initial increase followed by a slow but steady decrease. This in- 
dicates antagonism between the hydrogen ion and the anion. 
It is also interesting to note that, although arsenic is usually regarded 
as a very toxic substance, the effect of the arsenate does not seem to be any 
greater than that of any other salt with trivalent anion. 
Amojng the organic salts only formate gave useful results. The osmotic 
effects produced by the high concentrations necessary in the cases of the 
propionate, lactate, butyrate, and salicylate cause a very sudden fall of 
resistance. The effect upon the tissue, however, is very different from that 
produced by a salt like sodium citrate. In the former cases the tissue simply 
becomes flabby without undergoing any other noticeable change. In the 
case of sodium citrate (and similar salts), where the rapid fall is not due to 
plasmolysis, the tissue becomes decidedly gelatinous and presents a very 
different appearance. 
The results indicate that the effects upon permeability depend upon 
the valency of the anion regardless of whether the salts are organic or 
inorganic. 
Laboratory of Plant Physiology, 
Harvard University 
BIBLIOGRAPHY 
1. Raber, O. L. A quantitative study of the effect of anions on the permeability of plant 
cells. Jour. Gen. Physiol. 2: 535. 1920. 
2. Osterhout, W. J. V. The effect of acid on permeability. Jour. Biol. Chem. 19: 493. 
1914. 
