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1896] MOVEMENT AND TRANSMISSION OF IMPULSES IN PLANTS 297 
were made in the dead portion of a stem or petiole of Mimosa, 
but no great reliance is placed in such results. 
Dr. Cunningham has repeated the tests of transmission 
through dead portions of stems, and was able to send an impulse 
through stems consisting of alternating living and dead sections. 
The above experiments, giving similar results in the hands 
ofa great number of workers, demonstrate conclusively that 
transmission may be accomplished in portions of the plant in 
which no turgid cells occur, and consequently in which no 
hydrostatic disturbance is possible. 
With such facts in evidence the next step was naturally the 
determination of the question as to whether or not a hydrostatic 
disturbance constituted an impulse. Three methods were used. 
A number of young, healthy plants 4o™ in height were brought 
into the experiment room, and after being cut off near the sur- 
face of the soil, the bases of the excised stems were set in beak- 
ers of distilled water. The immersed portion (10™ long) of the 
stem was split and stripped in such manner that a large surface 
composed of active cells was exposed. When the leaves had 
regained their normal position half an hour later, with the air 
temperature at 28-30° C., the water in the beaker was withdrawn 
and quickly replaced by a saturated solution of potassium 
nitrate without mechanical disturbance to the shoot. Although 
the endosmotic action of the potassium must have resulted in 
the almost instantaneous withdrawal of a large quantity of water 
from the “Schlauchzelle” and other exposed tissues of the base 
a the stem, no reaction followed. The leaves were found to be 
in their usual sensitive condition after the experiment, when 
Contact or incision stimuli were applied. 
The bases of the stems of small plants were sealed securely 
into'a glass tube roo long, 1° internal diameter, filled with 
“ater, which connected at the other end with a leaden tube 
3o™ long leading into a receiver of a capacity of 4 liters, with a 
vacuum ot 70™. of mercury. When the leaves had regained 
— hormal Position, with the temperature at 28-32" C., the 
°pcock leading into the vacuum was turned, allowing the full 
