THE MECHANISM OF MOVEMENT AND THE DURATION 
OF THE EFFECT OF STIMULATION IN THE 
LEAVES OF DIONAEAi 
William H. Brown 
Introduction 
Charles Darwin (1875) appears to have been the first to investigate 
the mechanism of leaf closure in Dionaea. He marked the upper 
surface of the leaf with ink-dots and found that the distances between 
these decreased slightly as the leaf closed. From this he concluded 
that closure is due to the active contraction of the upper surface of 
the leaf. De Candolle, as a result of his morphological studies of 
Dionaea, advanced the idea that the opening and closing movements 
of the leaf are due to changes in the turgescence of the parenchyma of 
the dorsal region. Batalin (1877) concluded that movement is here 
accompanied by a small amount of actual growth. Munk (1876) 
expressed the opinion that the closure of the leaves is mainly due to 
the contraction of the upper surface but added that there is also an 
expansion of the lower surface. This writer supposed that water 
passes from the cells of the upper to those of the lower region. Mac- 
farlane (1902) believed that there are structures in the leaves of 
Dionaea which resemble animal muscles. The prevailing opinion thus 
seems to have ascribed the closure of Dionaea leaves to the contraction 
of the dorsal region of the leaf. 
The experiments here reported were carried out at the Laboratory 
of Plant Physiology of the Johns Hopkins University, and the writer 
is indebted to Prof. B. E. Livingston for valuable assistance in the 
experimentation and for editorial help in connection with this paper. 
The plants used were very kindly supplied by Dr. W. D. Hoyt. The 
fact that much of the literature dealing with plant movements is not 
available at this Bureau has rendered the above discussion of the 
literature necessarily very incomplete. 
Mechanism of Stimulation Movements 
The leaves of Dionaea show two distinct types of closing move- 
ments. In the first of these, if the leaf is stimulated and the stimulat- 
^ Botanical contribution from the Johns Hopkins University, No. 48. 
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