PROPERTIES OF THE LEAF OF DIONiEA. 
as much so as the distal end. (2) That in any line drawn across the midrib on the 
outer (under) surface of the leaf from side to side, a point can be found on either side 
which is negative to all other points, the negative point being situated nearer to the 
border of the leaf than to the midrib (p. 38), and finally that the distribution of 
tension is the same on the under surface as the upper (p. 42) and that opposite points 
are always equipotential.* In § 3 the difference of potential between the most 
negative and the most positive points of the outer (under) surface of the leaf is found 
to be O'04 to 0’05 Daniell. In § 4 the question of the seat of the electromotive 
forces on which this and the other observed differences are dependent is discussed. 
From preliminary considerations he concludes that inasmuch as it is out of the 
question “ das Blatt zu zerstiickeln ” so as to investigate the electromotive properties 
of its parts separately, the only way is to start from the well grounded assumption 
that wherever the same organisation exists there will be similar arrangement of 
electromotive forces, and accordingly that in the individual cell the electromotive force 
will show a distribution which has a definite relation to its long axis. Hence, inasmuch 
as the form of the cell admits of but few possibilities, we may, by ascertaining which 
of these possibilities when taken in relation with the known arrangement of the 
cells in the leaf, affords the best explanation of what is actually observed in the dis¬ 
tribution of electrical tension on the surface of the leaf, select that which accords best 
with fact. In order to get at this result Professor Munk employs a method of investi¬ 
gation which I shall not endeavour to describe in detail, but content myself with 
stating that it is founded on the assumption that it is possible to represent the living 
cell, as regards its electromotive properties, by a zinc cylinder having a zone of copper 
and surrounded by a uniform layer of a moist conductor ;t and that a schema or model 
made up of a number of such cylinders arranged like the cells of any living part of a 
plant would exhibit electromotive properties similar to those of the organ it represented. 
Stated as shortly as possible, the actual arrangement of the parenchyma cells of the 
leaf of Dionsea is as follows : in the lobes the cells run all in one direction, namely, 
parallel to the veining and at right angles to the midrib. In the midrib the cells of 
the ridge (under surface) run longitudinally, but those of the trough (upper surface) 
are continuous with those of the cells of the lobe. For reasons which need not be 
here entered on (see p. 86) Professor Munk considers that the arrangement which 
determines the electromotive properties of the leaf, is that of the cells of the lobe- 
parenchyma of which the long axes are parallel to the surface of the lobe and at right 
* “An der oberen Blattflaclie die gleicbe Vertbeilung der Spannungen herrscht, wie an der unteren 
Blattfiache’’ (p. 42). “ Dass die absolute Grosse der Spannungen an der oberen und an der unteren 
Blattfiache die gleicbe ist ” (p. ). 
f “ Die einzelne Parenchymzelle entspricht hinsichts ihrer Krafte dein einzelnen Metallcy Under ” (p. 96). 
Du Bois-Reymond’s schema of an electromotive element of muscle is a copper cylinder with a zinc zone 
surrounded by a uniform layer of a moist conductor. For the plant electromotive element, according to 
Munk, the sign must be reversed. The cylinder must be zinc and the zone copper. 
B 2 
