570 
S. C. BROOKS 
experiments on the rate of recovery in saccharose solutions are of 
considerable importance. In Table 2 and Figure 3 are presented the 
data of a characteristic experiment with saccharose, together with 
those of similar experiments with potassium nitrate and calcium 
chloride for purposes of comparison. Saccharose affects the permea- 
bility of the protoplasm in the manner typical of a salt of a monovalent 
kation, but the changes occur with less rapidity. It is therefore unsafe 
to use saccharose as an indifferent medium ; a properly balanced mixture 
of salts should rather be used when a solution is desired in which to 
maintain the normal permeability of living cells, as is evident from a 
comparison of Figures 2 and 3, disregarding (as previously explained) 
the first 20 minutes of the experiment. 
Summary 
1. The permeability of the protoplasm of Taraxacum oijicinale 
Weber remains nearly or quite normal in a balanced solution consisting 
of a mixture of sea water and calcium chloride, such that the ratio of 
univalent to bivalent kations is approximately seventy to fifteen. 
2. Salts of univalent kations in pure solutions cause a rapid increase 
in permeability. 
3. Salts of bi- and trivalent kations cause a very great decrease in 
permeability. 
4. Saccharose penetrates protoplasm quite rapidly, and affects 
permeability like a univalent kation. 
Laboratory of Plant Physiology, 
Harvard University 
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