PROPERTIES OE THE LEAP OP DIOM2A. 
7 
Professor Munk’s paper does not contain any statement of his conclusions. For 
further reference I have arranged them as follows, in the order in which they have 
been referred to in the preceding sketch :— 
1. Each individual parenchyma cell of the leaf corresponds, in respect of its electro¬ 
motive properties, with a zinc cylinder zoned with copper and surrounded by a uniform 
layer of moist conductor. In other words, the nearly cylindrical cells are endowed 
with electromotive forces such, that positive electricity is driven from the middle of 
each cell towards each of its poles, i.e., the middle is negative to the poles (p. 97). 
2. The electromotive properties of the whole leaf (pp. 47-51) in the unexcited 
state are represented by those of a schema (see diagram, fig. 20, a), consisting of such 
cylinders arranged in the same order as its cells (p. 87). 
3. On excitation, the cells of the upper layer of the leaf undergo a diminution of 
electromotive force, those of the under layer an increase, i.e., the middles of the cells 
become less negative than before in the upper layer, more negative in the lower layer 
(p. 152). 
4. The diphasic character of the variation is not due to the fact that the individual 
cells undergo opposite changes in succession, but to the interference of the opposite 
electromotive actions of the upper and under cells, of which the time relations are 
different (see diagrams 29 and 30 and p. 142). 
5. The effect of an excitation is in no way dependent on its seat (p. 138). 
6. The electromotive activity of the cells has no relation to their water-content 
(p. 158).* 
* The author’s criticisms of my methods and conclusions will be best considered in connexion with the 
several subjects to which they refer. His paper contains some misconceptions which it will be convenient 
to correct in this place. One of the most important, as having led other writers into error, is founded on 
a casual expression of mine contained in a lecture at the Royal Institution in 1874, to the effect that the 
excitatory motion of the leaf is identical with muscular motion. Ho such expression is contained either 
in my communication to the Royal Society, or in the translation of it which appeared shortly afterwards 
in the ‘ Centralblatt.’ (“ Ueber electrische Vorgange im Blatte der Dioncea muscipula .” ‘ Central- 
blatt f. d. Med. Wissensch.,’ 1873, Ho. 53.) If Professor Munk had considered the context, he would 
have seen that in my lecture I meant nothing more than that both motions are expressions of the 
same elementary endowment of protoplasm—that of changing its form on excitation. I held then, 
and hold now, that, as regards what happens in the living protoplasm, the mechanical effects of excitation 
in the contractile parts of plants and animals are closely related. As to the mechanism by which the 
changes of form of the excitable organs of plants are brought about, nothing was said in my paper. 
I took for granted the explanation usually given, founded on Beuckk’s experiments. I had not become 
acquainted with the then recently-published researches of Pfeffer on the excitability of plants 
(‘ Physiologische Untersuchungen,’ von Dr. W. Pfeffer. Leipzig : 1873). 
As regards the original experiments by which I demonstrated the fact that the leaf of Dionasa responds 
to excitation by an electrical disturbance analogous to the excitatory valuation of muscle, Professor Munk’s 
