1910) BROWN & SHARP—CLOSING RESPONSE IN DIONAEA 301 
Summary 
The closing response in Dionaea depends upon the intensity 
rather than upon the number of stimuli, the number of stimuli required 
varying in the inverse order of their intensity. 
Response is normally brought about by the compression of certain 
cells at the bases of the sensitive hairs, but the compression of other 
cells of the blade also causes closure, and it is probable that the latter 
cells are equally sensitive with the cells at the bases of the hairs, as is 
indicated by electrical and thermal stimulation. 
The closing response follows the application of mechanical, elec- 
trical, and thermal stimulation. It also follows a combination of 
stimuli of two kinds when consecutively applied, the individual stimuli 
being of an intensity such that either alone would be insufficient. 
The effect of mechanical stimulation is due to compression of cells, 
and not to contact with a hard object, continued pressure, or release of 
pressure. The failure of the leaf to respond to shaking is probably 
connected with the small inertia of the sensitive hairs, and the slight 
resistance offered by the air 1o their passage through it. 
Water at room temperature causes closure only when it bends a 
sensitive hair. 
After one mechanical stimulus there is a short period during which 
a second mechanical stimulus is ineffective. 
The writers are indebted to Dr. W. D. Hoyt for collecting the 
plants used, and for help during the course of the work; to Professor 
D. S. Jounson for his encouraging interest; and to Professor B. E. 
Livincston for valuable aid in the prepexenee of this paper. 
Jouns Hopkins UNIVERSITY 
BALTIMORE, MARYLAND 
LITERATURE CITED 
I, Batattn, A., Mechanik der Bewegungen der insektenfressenden Pflanzen. 
Flora 35:54-58, 105-111, 129-154. 1877 
BuRDON-SANDERSON, J., On the electromotive properties of the leaf of 
Dionaea in the excited and unexcited states. Phil. Trans. Roy. Soc. London 
173:1-53. 1882. 
- Darwin, Cuartes, Insectivorous plants. 1875. 
Deruer, W., Pflanzenphysiologisches Prakticum. 1888 
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