240 BOTANICAL GAZETTE [SEPTEMBER 
abscissae concentration of the plasmolyzing solution would be a 
straight line. It was found, however, that such a curve was 
concave to the axis of the ordinates. This indicated a decrease in 
the rate of recovery with time. Firrinc considers this to establish 
the fact that such salts cause a progressive decrease in the per- 
meability of the protoplasm. He considers the possibility that 
exosmosis might have occurred in his experiments, and cites 
experiments which supposedly show that all possible exosmosis had 
taken place during the preliminary 4-6 hours’ exposure of the 
tissues to distilled water. There are serious discrepancies in his 
data, such as the fact that a solution of a higher osmotic pressure 
is required to produce plasmolysis in tissues from which all possible 
exosmosis is supposed to have taken place than is required to 
produce it in otherwise comparable tissues from which no exosmosis 
occurred. It is probable that Firrmnc has some important 
variables in the method which he has employed, and since he has 
failed to investigate the effect of salts of monovalent kations on 
exosmosis, it is probable that the supposed decrease of endosmosis 
is in reality an increase of exosmosis, which would have the same 
effect on the rate of recovery. Firtinc also states that the cells 
_are wholly impermeable to salts of bivalent and trivalent kations, 
with the possible cP preiuea of strontium. This i is in conflict with 
ai. = i i 
METHODS NOT aoe PLASMOLYSIS 
In rapidly elongating plant tissues there is usually a very con- 
siderable pressure exerted by the protoplasts against the cell walls 
which confine them. If all the cell walls of the stem are thin and 
elastic, ay) whole stem will be kept i in a stretched condition by’ this 2 a 
4 ae cells, ; such as fib ova: 01 la: oe - 
- . or opal cells, which do not yield to internal pressures ieee eS 
tissue. If we cut such a stem or aateneln aa € : 
