BOTANY: 5. C. BROOKS 
573 
Strips of peduncle were fastened at one end in a horizontal position in a 
suitable dish, and in such a manner that the free end moved horizontally 
as the curvature of the strip changed in response to changes in its tur- 
gidity. The movement of the free end was then observed by means of 
a microscope. The strips were first allowed to come into osmotic 
equilibrium with a solution originally very nearly isotonic with the 
cells. A slight increase in concentration was then made, and the time 
required by the strip to return to its original position after the loss of 
curvature thus caused, was noted. Immediately upon the recovery of 
a strip, the concentration of the solution bathing it was again increased, 
FIG. 3. FIG. 4. 
FIG. 3. THE EFFECT OF PREVIOUS TREATMENT OF PEDUNCLES OF TARAXACUM WITH 
SOLUTIONS OF DIFFERENT SALTS ON THE CONDUCTIVITY OF DISTILLED WATER IN CON- 
TACT WITH THE TREATED TISSUE. 
FIG. 4. THE EFFECT OF PREVIOUS TREATMENT OF PEDUNCLES OF TARAXACUM WITH 
PURE AND BALANCED SALT SOLUTIONS, ON THE CONDUCTIVITY OF DISTILLED WATER 
IN CONTACT WITH THE TREATED TISSUE. 
and the 'recovery time' again noted. In this manner a series of 're- 
covery times' of the same strip was obtained. In the absence of exos- 
mosis the molecular increase in concentration, divided by the ' recovery 
time' affords an empirical measure of the rate of penetration of the 
plasmolysing substance. 
The data graphically presented in figures 5 and 6, show that the rate 
of recovery was increased by the salts of the monovalent kations, and 
by saccharose, while in the salts of bi- and trivalent kations it was less 
than that in the balanced solution. The first group exhibits also a 
characteristic secondary decrease in the rate of recovery which may be 
due to exosmosis from the cells. 
