292 BOTANICAL GAZETTE [APRIL 
tested at position 0, but no difference was observable between the 
response in this case and that in which only a single cell was used. 
Partial closures were obtained before the complete closures in four 
cases with the first arrangement of contacts, and in a single case 
with the second arrangement. These are indicated by footnotes 
below the table. 
TABLE I 
NUMBER OF ELECTRIC SHOCKS REQUIRED TO PRODUCE COMPLETE CLOSURE WITH 
VARYING INTENSITY OF CURRENT; SHOCKS AT INTERVALS OF 15 SECONDS 
CONTACT ON SENSITIVE HAIR AND PETIOLE CoNnTACTS ON KEEL AND PETIOLE 
ay nr No 
Position of No. Position of F 4 5 
F Ol Oboe hee loge bog |: 6 - of ).e [tt a3 
coil task coil test 
Pn) Pe Le Fos Caneel 
Number of | 1 | 1 | 1 | 1 | 4*| 6f/ 7 |rof | Numberof | 1/1 {1 {| 2)? 3t| 4 
shocks re- s re- 
quired for| 2 2\21 3t) if 26 | quired for | 2 aA ee ae call 
complete complete 
closure 3 I closure 3 I 
: .e[2.5|4°5 
Average .......|1.0|1.3/1.5/3-5/3.5|7-0|18.0] Average... .... 1.0/1 .0|2.0|1-5|2-5 
Po See 
* Partial closure with 3 shocks. t Partial closure with 5 shocks. 
+ Partial closure with 2 shocks. { Partial closure with 9 shocks. 
It is apparent from these tests that closure is due to intensity of 
stimulation rather than to number of stimuli, and that there exists 
a definite after-effect with a duration of over 15 seconds, the summation 
of these after-effects finally producing the response in the case of 
the weaker electric shocks. 
We have heretofore considered mechanical stimuli as though all 
were of the same intensity, a condition which appears to be true | 
if the hair is markedly bent. As has been stated, leaves kept at a 
temperature of 15° C. usually close on the application of the secon 
stimulus, and in this case it appears to make no difference whether the 
bending of the sensitive hair is comparatively slight, or great enough a 
bring the hair against the leaf. At higher temperatures the leat 
responds to one stimulus as frequently with slight as with more marked 
bending of the sensitive hairs. This is shown even more conclusively 
by the fact that at a temperature of 15° C. the leaf fails to respond when 
the hair is bent down against the leaf by one movement, while i 
_ bending, if accomplished by two movements, brings about response 
