1896] MOVEMENT AND TRANSMISSION OF IMPULSES IN PLANTS 299 
compress the stem quickly without communicating a mechanical 
disturbance to the plant. It is also difficult to give the com- 
pression without crushing the tissues of the plant. It seemed, 
however, that in the instances where the above faults were 
avoided no reaction followed the compression, though no 
conclusions are based on this result. 
In conclusion it may be said that the following points are 
somewhat firmly established: (1) Impulses may be transmitted 
by Mimosa and Oxalis through dead portions of stems and 
petioles in which the conditions are such that a transmission by 
the cell-wall or the water in the wall only is possible. (2) Great 
variations in the pressure exerted on portions of the plant in 
such manner as to set up hydrostatic disturbances extending 
throughout the entire plant are not followed by reactions; 
hydrostatic disturbance therefore does not constitute an impulse. 
It is to be noted, however, that while it is proven that an im- 
pulse may be transmitted by a wall of a dead cell, it does not 
follow that the entire transmission from the point of reception 
to the motor organ is accomplished by such means alone. It 
seems quite possible that protoplasmic action plays apart at both 
ends of the chain connecting the two points, and that while a 
hydrostatic disturbance does not constitute an impulse, it may 
play a minor part in its transmission. 
_ The entire problem, together with that of the developmental 
history of such highly specialized forms of ‘“sensitiveness” as 
those exhibited by Mimosa, must be followed to their solution 
in the tropical habitats of the plants. 
Tue Stare University oF MINNESOTA. 
EXPLANATION OF PLATE XIII. 
Fi 
