144 Scientific Intelligence. 
the leaf. This current he calls the normal leaf-current. 
instead, the leaf stalk is placed on the electrodes (the leaf remain- 
ing united t 0 it) in such a way that the extreme end of the stalk 
rests on one electrode, and a part of the stalk at a certain dis- 
tonige from the leaf on the other, a current, called a stalk-current, 
is indicated, opposed to that in the leaf. To show these currents, 
it is not necessary to expose any cut surface to the electrodes. 
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by oe wee its length one-half, this deflection was 
increased t 65, 90 and 120. Partially severing the leaf gave 
the same pees as if it was completely cut o 
If the leaf is placed on the — as before, on introducing 
the petiole into the circuit of a small Daniell, the deflection is 
increased when the current passes lows the petiole, that is, from 
On reversing the current the deflection is diminishe 
If, the leaf being so placed that the normal leaf-current. is 
indicated by a deflection to the left, a fly is allowed to creep into 
it, it is observed that the moment the fly reaches the interior (so 
as to touch the sensitive hairs on the upper surface of the lamina) 
the needle swings to the right, the leaf at the same time closing 
on the fly. 
The fly having been caught does not remain quiet, and ea ch 
= it moves, the needle again swings to the right, always com- 
for 
‘Pica ng the : af- mc and leaf on the electrodes as before, the 
ae current is seen to be increased, whenever the leaf is irritated 
as abo 
If the open leaf having been placed on the electrodes, one 0 
the concave surfaces is pierced with a pair of platinum needles 
connected with the — coil of a Dubois Ray ‘mond indue- 
tion apparatus, it is observed that when the circuit is closed the 
needle swings to the Sek as when irritated mechanically. No 
difference is observed when the induced current is reverse 
The observation may be repeated any number of times, but no 
effect is produced unless an interval - — ten to twenty seconds 
has elapsed since the preceding irritat 
if the part of the concave surface of the leaf nearest the petiole 
is excited, the swing to the right is always preceded by a momen- 
tary jerk of the needle to the left. This effect cannot be produced 
by irritating any other part of the concave surface of the leaf. 
An interval of from a quarter to a third of a neat always 
intervenes between the act of irritation and the negative varia 
tion.— Nature, ix, 75. B. Gy Fs 
