298 BOTANICAL GAZETTE [ocToBER 
force of the vacuum to act on the base of the stem. Inno 
instance was a reaction obtained. The usual tests showed a 
normal degree of sensitiveness in the plant. 
The two experiments above described must lead one to con- 
clude that diminished hydrostatic pressure does not constitute 
an impulse. It is, of course, open to belief that greater varia- 
tions in pressure or a more sudden application of the same might 
be followed by a reaction. 
To avoid a misconception of the effects of such diminution 
of pressure on the cell contents, attention is called to the fact 
that the ““Schlauchzelle” form a series of continuous tubes, the 
contents of which freely communicate by openings in the cell 
walls, and that variations in pressure on any part of the system 
are quickly distributed through the entire system, as is demon- 
strated by the following experiment. 
In order to test the effect of increased pressure on the plant, 
shoots were securely sealed into a short section of glass tubing, 
as above, by means of a rubber stopper bound in place by wires. 
The tube was filled with water and the other end connected ina 
similar manner with a leaden tube, with an internal diameter 
of 3-4™" and 1.5™ in length, leading to the chamber of a com- 
pression air-pump (see plate ). When the leaves had regained 
a normal position in an air temperature of 26-32° C., by a sud- 
den stroke of the handle of the pump a pressure of 3-8 atmos 
pheres was suddenly exerted on the base of the stem, but 10 
reaction followed. That the increased pressure was exerted 
throughout the plant was proven by the manner in which wate 
poured from the clipped end of a distant leaflet, and that it 
passed through the “Schlauchzelle”’ was shown by stripping 
away the tissues external to these cells. The pressure was thus 
communicated to distant parts of the plant within a second from 
the time of its application. 
As another test, with its object similar to the above, 4 com- 3 
pressive pressure was quickly applied to various parts of : 
plant by the fingers, forceps, or other appliances. In som 
instances reactions were obtained. It is extremely difficult 
