250 BOTANICAL GAZETTE [MARCH 
Experiments on dead tissue (killed by heat or by formalin or 
allowed to die a natural death) showed that the results described 
above are due entirely to the living cells. 
A very marked decrease of permeability may be produced by a 
considerable variety of other salts. The addition of these salts in 
solid form simultaneously increases the conductivity of the solution 
and decreases the conductivity of the tissue. This affords the 
most convincing proof that the change in the conductivity of the 
tissue in these experiments cannot be due to any cause other than 
a change in permeability; for the concentration of the ions of the 
sea water remains unchanged, and if they were able to penetrate 
as freely as they did before the addition of the salt, the resistance 
would not increase. It would, in fact, diminish on account of the 
increased conductivity of the solution held in the cell walls, as is 
clearly shown by experiments on dead tissue. 
It may be remarked incidentally that these experiments effectu- 
ally dispose of the possible objection that the current passes between 
the cells but not through them. Were this objection well founded, 
the decrease in conductivity could be explained only as the result of 
a decrease in the size of the spaces between the cells. This decrease 
could not be brought about except by greatly reducing the thickness 
of the cell walls. Both macroscopic and microscopic measurements 
show most conclusively that this does not occur. The contrary 
effect would be produced by the addition of salts in solid form, 
for they would tend to produce plasmolysis and thereby to increase 
the space between the cells. 
As these remarkable changes in permeability seemed to produce 
no bad effects, it occurred to the writer to see whether the proto- 
plasm could endure still more violent alterations without perma- 
nent injury. In order to test this the following experiment was 
performed. A lot of tissue was found to have in sea water a resist- 
ance of toro ohms. It was placed in CaCl, 0. 278M, which had the 
same conductivity as the sea water. At the end of ten minutes 4 
reading was taken which showed that the resistance had risen to 
1500 ohms. The material was then placed in NaCl o.52M, which 
had the same conductivity as the sea water; at the end of ten 
minutes the resistance was 880 ohms. The experiment was COR 
