The Sun.
London, England, 1866-10-18 00:00:00

The Sensitive Plant.

Dr. George Sigerson writes as follows to the 1
Athcnnwunt :—" Some months ago it occurred to me
that the motion of the folioles of the sensitive plant,
on being touched by the finger, might be due to the
transmission or interchange of electricity between
the two points in contact. Impressed with this
idea I tooli the opportunity a few days ago of put-
ting the matter to the test, by using for the pur-
pose of touching the folioles a non-conductor, a
steel conductor, and the finger. The experiment
quite answered my expectations, as the subjoined
letter from my friend, Professor Divers, will testify.
The plant, I should state, was in flower, and at this
period it is probably more sensitive than at other
times. On the 12th of August I experimented
three or four times; and on the 19th I again re-
peated these trials with a similar result, so that the
care-taker spontaneously remarked upon the diffe-
rence of the effects produced. They were these :
" On touching gently and even lightly pressing the
folioles with glass they remained as they were; on
touching them with steel heid in the fingers, or (in
other instances) with the fingers, they made their
usual movement. Again, before I applied these
tests, a gentleman asked me to explain how it hap-
pened that the plant moved more readily when
touched by any of his children than by himself
He had seen this take place several times and could
not account for it. I thought it harrnonisedto
exactly
with my theory, and have since had
reason be-
lieve that with the same individual the action
will
be more evident when he is in a tonic state (if I
may
use the expression) than when he is exhausted
to provestedand
weary. Although what I have shown goesi
that the passage of electricity between the points in
contact will account for the movement of the folioles
in such instance, I do not mean to say that when-
ever the foliole moves there must be contact with a
conductor: For I hold it possible that the plant may
be capable of developing within itself sufficient of
such force to close its folioles (a seemingly protec-
tive movement) if roughly handled. From what I
have observed with regard to the sensitive plant, it
appeared to me probable that the fly-trap movement
of the processes of the Dionda muscipula was due to
the same cause. Having gently touched those ex-
teriorly, I was disappointed to find no result pro-
duced. Laying the tip of the little finger (in two
cases) softly -within the expanded processes, I found
them to close, whereupon I immediately withdrew
it, that there might be no possibility of injury to the
plant. I thought the fact almost valueless, as there
was no opportunity of testing what wouldbethe action
with a non-conductor. However, but a few moments
had elapsed when my attention was drawn to a dis-
tinctly painful sensation in the ulnar nerve at the
right elbow, it being the little finger of the right
hand I had used. This sensation persisted for some
time, then imperceptibly passed away. I admit that
the subject is capable of many more tests and much
more development than I can give it in this letter
or at this time. It is my intention, however, to pur-
sue the investigation, confident that it will be re-
cognised as one of considerable importance and re-
plete with interest. Now, when the rigid limit drawn
by
the old naturalists between the animal and ve-re-
table kingdoms has been found untenable, there will
be many, I presume, to admit that a priori there is
no absolute reason why individuals of the former
kingdom should be endowed with power of generat-
ing electricity essentially denied to all members of
the latter; few also, I believe, will assert the ante-
cedent impossibility of any of those plant-organs,
termed vessels,' and ribs,' subserving in a very re-
stricted sense, it may be, the purpose of nerves."
The following is a copy of the letter from Dr. Divers,
referred to above : " Charing-cross Hospital, Lon-
don, Aug. 15, 1866.—My dear Dr. Sigerson,—At
your request I am very glad to be able to acknow-
ledge witnessing the interesting fait you showed me
at Kew on the 12th of the present month concern-
ing the sensitive plant. The fact was this, that while
the leaves of the plant proved highly sensitive to the
slight contact of your finger, or of a piece of steel
held in your hand, they were not sensitive to the
similar contact of glass. This fact was new to me
at the time."