294 BOTANICAL GAZETTE [APRIL 
It is seen at once that with increasing length of time interval the 
number of stimuli required to produce a response increases also. 
Considering only the number of stimuli required for complete closure, 
these results are tabulated in table ITI. 
TABLE III 
NUMBER OF STIMULI NECESSARY TO PRODUCE COMPLETE CLOSURE, 
THE TIME INTERVAL VARYING FROM 20 
SECONDS TO 3 MINUTES 
TIME INTERVALS BETWEEN STIMULI 
EXPERIMENT NO. 
2oseconds | 1 minute | 2 minutes | 3 minutes 
ROO Meme yree 2 3 5 8 
LS ES ar Seog NL 2 iz 6 9 
Pe en ae ae OE 2 4 6 9 
Roto ee ee 2 5 6 
RE ee ates ay ae: 7 
OR era a gees ure 7 
Avetage.: 2.7... 2.0 3-8 6.2 8.7 
The averages from this table are plotted on the graph of jig. 1 
in which the abcissas represent the length of the time intervals 
1 g, petween stimuli, and the 
ordinates the average num- 
ber of stimuli required for 
complete closure. In this 
region the graph shows only 
a slight curvature. It 3 
nearly a straight line, which 
would seem to denote that 
at intensities ranging from 20 
seconds to 3 minutes—and of 
course for these particular 
plants—the number of stimuli 
necessary for complete Tes 
ponse varies almost directly 
with the length of the inter 
vals. 
It may be concluded from the foregoing that leaves seem to respond 
by closing to a definite amount of accumulated effect, possibly the 
oL. 
| 
a me x 
Fig. 1 
