Permeability of the Pulvinus of Mimosa piidica. 83 
The results of one experiment are given in Table V, and a graphic 
representation is shown in Fig. 5, where the experiment was begun at 38° C., 
and the temperature was allowed to rise at first at a rate of 2 ° C. in six 
minutes, later somewhat more slowly. From 38° to 5o°C. there is practically 
no change in permeability when the conductivity readings are calculated to 
a constant temperature (64° C.) on a basis of a change of 2 per cent, per 
degree. Only after 48° or 50° is there a distinct rise in the rate of 
exosmosis, which rapidly reaches a maximum as the impermeability of the 
protoplasm breaks down. With the loss of salts from the cell the gradient 
of concentration lessens, and so the rate of exosmosis slows down and finally 
falls rapidly in spite of the increased permeability. 
Of course in such experiments as these, where the temperature is above 
what may be termed normal, the time factor plays a large part. Experi¬ 
ments with different rates of rise of temperature would thus give curves of 
