Measurement of Rate of Shrinkage of Turgid Tissues . T 291 
Measurements were made at intervals, and when a contraction seemed com- 
plete a somewhat stronger solution was substituted. By this means it was 
found that the cells of the same section behaved differently in the same 
solution, and some light was also thrown on the behaviour of the tissues 
with hypertonic solutions. 
In one experiment, in which the section was irrigated successively with 
solutions of 0-33, 0*25, and 0*30 grm. M. sugar, cells corresponding in position 
to B, B (Figs. 3 and 4) were observed, and each passed through the phases 
illustrated in Fig. 5. 
Now the cells of which this cell is typical are just plasmolysed by the 
solution 0-23 grm. M. and have no longer therefore any turgor, yet on the 
addition of stronger solutions they undergo further shrinkage. Their walls 
In water 
After 2 hours 
•23gm M.sugar 
After 1 % hours 
•25gm. M.sugar 
After 2 hours 
•30gm. M.sugar 
Fig. 5. A single cell from a longitudinal section of a turgid onion leaf, showing stages in 
plasmolysis with successive sugar solutions, drawn to scale, (r) In water. (2) Alter 2 hours 0*23 grm. 
M. sugar. (3) After hours 0*25 grm. M. sugar. (4) After 2 hours 0-30 grm. M. sugar. 
first showed signs of crumpling after some hours in 0-3 grm. M. sugar, and 
with still stronger solutions the walls collapse altogether upon the shrunken 
protoplast. This complete collapse of the inner cells appears to be due in 
the first instance to the constraining effect of the palisade cells, which were 
all plasmolysed by the 0-3 grm. M. solution, but it also probably indicates an 
imperfect permeability of the cell-walls for sugar molecules. In any case, 
the cell-wall does not always remain completely extended after the proto- 
plast is withdrawn fiom it, as is often assumed to occur in the plasmolysis of 
plant cells, but with hypertonic solutions other factors cause its further 
contraction. This leads to a prolonged shrinking of the whole tissue with 
hypertonic solutions, which is not primarily a question of plasmolysis, but is 
a sort of mechanical ‘ settling down ’ of the cellulose walls. 
