77 
Permeability of the Pulvinus of Mimosa pudica . 
or the result. The association of increased permeability with contraction, 
apart from cooling or mechanical stimulation, is well shown in Table III, 
where the contractions are autonomous. 
It is to be noted that in Tables I and II the pulvinus recovers less and 
less fully after each contraction, so that the angle in column A gets less as the 
experiment proceeds. On the other hand, the extent of the contractions 
seems to get greater and greater, so that the angles reached after contraction, 
and shown in column A\ also tend to get less. This is well shown in 
Fig. 2. 
The observations here described show that the loss of turgor in the cells 
of the lower half of the pulvinus cannot be explained by a rapid exosmosis 
of osmotic substances. The loss of turgor must almost certainly be due to 
the disappearance or inactivation of these substances. As to the mechanism 
of this process we have at present no knowledge; it is suggested that 
changes in the adsorptive power of the colloids of the cell play a large part. 
Autonomous Contractions of the Pulvinus. 
While carrying out these experiments a very interesting and, in the 
case of Mimosa , an entirely new phenomenon was met with, that of a series 
of rapid contractions of the pulvinus similar to those due to shock, but 
