. 244 BOTANICAL GAZETTE [SEPTEMBER 
tion of the solution. The kations are of particular importance. 
All monovalent kations (excepting the hydrogen ion) produce only 
‘an increase in permeability of the protoplasm. This increase, 
reversible in its first stages, finally leads to death and complete 
permeability. Bivalent and trivalent kations and the hydrogen ion 
cause a temporary and reversible decrease of permeability which is 
followed or superseded by an increase which is irreversible and leads 
to death of the cells. In a balanced solution such as sea water the 
resistance remains constant provided the laboratory conditions are 
such as to maintain the full vitality of the tissue. We have here 
a method of determining quantitatively the permeability of the 
protoplasm at any instant, and the data secured demonstrate the 
extreme importance of progressive changes in the permeability of 
protoplasm. It would be possible to imagine that the passage of 
an electrical current through the tissues was responsible, at least in- 
‘some measure, for the observed changes in permeability. It would 
be of advantage, therefore, to check the results of OSTERHOUT’S 
method by the use of some method entirely free from this possible 
objection. The method is also applicable to certain types of tis-_ 
ever the actua 
sue only, and it is desirable to extend to other types of plants the 
principles derived by the application of this method. 
The plasmolytic experiments of OsteRHouT (40) may be 
explained in the light of the experiments by the conductivity method _ 
in the following manner. During the time required to produce 
plasmolysis the permeability has considerably increased in the . . 
sodium chloride solution and somewhat decreased in the calcium . 
_ chloride solution. In that time much more sodium chloride has Le : 
penetisied the cell, therefore, than of the salts of the mixed solution 
in which the permeability remains normal, and these again more — 
? S : than the calcium chloride, and the osmo: ic gradients -s have changed 
accordingly. The osmotic pressures of the solutions which wil 
- produce visible gens will then have suffered an increase 
. ly i osmotic: solutions, and i in this order: calcium 
“he — very. little, ¢ the mix ion slightly more. and d sodium oe 
