1910] BROWN & SHARP—CLOSING RESPONSE IN DIONAEA 293 
If, however, the bending is so slight as to be scarcely apparent, three 
to five stimuli, rather than two, are usually necessary to produce 
response. It appears, in general, that in both mechanical and 
electrical stimulation closure is due to the amount of stimulation 
rather than to the number of stimuli, but the amount of stimulation 
appears not always to be proportional to the amount of bending of 
the sensitive hair. If this is true, the number of contact stimuli 
necessary to cause closure should increase with the length of the time 
TABLE II 
RESPONSE TO CONSECUTIVE CONTACT STIMULI AT VARYING TIME INTERVALS 
Tre 7 NUMBER OF STIMULI 
INTERVAL pasta 
BETWEEN 
stimuts. | MENT I 2 3 4 5 6 7 8 9 
tf = ~ 
20 2 _ + 
seconds 3 _ + 
4 a > 
x — P + 
I Pest eee eR de 
minute 3 — Si P o 
4 ae 
I _ a ~ 1 oe 
2 - ~ os _ P — 
oe 3 od eee te me 
minutes 4 _ — ae —_ r + 
& ~ es me Em —_ P + 
$45 Pete to ek 
I - = - - - P i Es 
‘ 2 ~ = _ P r + 
minutes 3 = on P + 
interval between them, since the effect of stimulation would be 
expected to disappear to a greater extent as the length of the time 
interval is increased. This hypothesis was tested with the result 
that leaves at a temperature of 15° C., stimulated mechanically at 
intervals of 20 seconds, closed with the second stimulus; when the 
interval was increased to a minute, they responded with 2 to 5 stimuli; 
at intervals of 2 minutes, a response was produced with 5 to 7 stimuli; 
while at intervals of 3 minutes, about 6 to 9 stimuli were necessary 
to bring about closure. These results are shown in table II, in 
Which — denotes no response; P, partial closure; +, complete closure. ; 
