258 
October, 1880, by M. Renevier.—Meteorological résumé of the 
year 1880 for Geneva and Great St. Bernard, by M. Plantamour. 
—Periodical movements of the ground indicated by the air- 
bubble of spirit-levels, by the same.—On the movements of the 
ground, by Col. von Orff. 
Reale Istituto Lombardo di Scienze ¢ Lettere. Rendiconti, 
vol. xiv., fasc. xvii.—On recent discoveries of Silurian fossils in 
the province of Udine, by M. E. T. Taramelli.—Synthesis of 8 
methylpyridine (8 picoline), by G, Zanoni, 
PI EEE eee 
SOCIETIES AND ACADEMIES 
; LONDON 
Royal Society, December 15, 1881.—‘‘On the Electromo- 
tive Properties of the Leaf of Dionez in the Excited and Un- 
excited States.” By J. Burdon Sanderson, M.D., F.R.S., &c. 
(Abstract.) f i 
The paper consists of five parts. Part I. is occupied by the 
examination of two experimental researches, relating to the sub- 
ject, which have been published in Germany since the date of the 
author’s first communication to the Royal Society, namely, that of 
Prof. Munk on Dionza, and of Dr. Kunkel on electromotive 
action in the living organs of plants. According to Dr. Munk, 
the electric properties of the leaf may be explained on the theory 
that each cylindrical cell of its parenchyma is an electromotor, 
of which the middle is, in the unexcited state, negative to the 
ends, and that on excitation the electromotive forces of the cells 
of the upper layer undergo diminution, those of the lower layer 
anincrease. He accounts for the diphasic character of the elec- 
trical disturbance which follows mechanical excitation by attri- 
buting it to the opposite electromotive reactions of the two layers 
of cells. According to this theory, each cell resembles in its 
properties the muscle-cylinder (‘‘ Untersuchungen,” vol. i. p. 
682, 1848) of du Bois-Reymond, differing from it in so far that 
its poles are positive instead of being negative to its equatorial 
zone. 
Dr. Kunkel’s experiments have for their purpose to show that 
all the electromotive phenomena of plants may be explained as 
consequences of the movement of water in the organs at the 
surfaces of which they manifest themselves. Neither of these 
theories is consistent with the author’s observations. 
Part II. contains a description of the apparatus and methods 
used in the present investigation. 
In Part ILI. are given the experimental results relating to the 
electromotive properties of the leaf in the unexcited state, a 
subject of which the discussion was deferred in the paper com- 
municated by the author (with Mr. Page) in 1876.1 The funda- 
mental fact relating to the distribution of electrical tension on 
the surface of the leaf when in the unexcited state is found to be 
that (whatever may be the previous electrical relation between 
the two surfaces) the upper surface becomes, after one or two 
excitations, negative to the under, and remains so for some time. 
Under the conditions stated, this difference of potential between 
the two surfaces occurs constantly ; the ‘differences of potential 
which present themselves when other points of the surface of 
the leaf are compared, may be explained as derived from, or 
dependent on, it. 
Part IV. relates to the immediate electrical results of excita- 
tion, z.e, to the electrical phenomena of the excitatory process. 
In investigating these the author takes, as the point of departure, 
an experiment which includes and serves to explain those ob- 
tained by other methods, and is therefore termed the ‘‘ funda- 
mental experiment.” It consists in measuring the successive 
differences of potential which present themselves between two 
opposite points on the upper and on the under surface of one 
lobe of the leaf, during periods which precede, include, and 
follow the moment at which the opposite lobe is mechanically or 
electrically excited. In this experiment it is found that, pro- 
vided that the conditions are favourable to the vigour of the 
leaf, the changes in the electrical relations of the two surfaces 
(called the excitatory variation) occur in the following order :-— 
Before excitation (particu- Upper surface negative to 
larly if the leaf has been pre- under. 
viously excited). 
At the moment of excitation. 
Sudden negativity of under 
surface, attaining its maximum 
in about half a second, the 
difference amounting to not 
less than y'; Daniell. 
™ «(On the Mechanical Effects and on the Electrical Disturbance conse- 
quent on Excitation, &c.,’” Proceedings, December 14, 1876. 
NATURE 
a i ies 
Rapidly increasing negativity 
of the upper surface, beginning 
1°5”, and culminating about 
3" after excitation, and"slowly 
subsiding. 
This subsidence is not complete, for, as has been said, the 
lasting difference between the two surfaces is augmented—the 
upper surface becoming more negative after each excitation 
(‘‘after-effect ”). 
When by a similar method two points are taken for com- 
parison on opposite lobes, the phenomena are more compli- 
cated, but admit of being explained as resulting from the more 
simple case above stated, in which only a few strata of cells are 
interposed between the leading off electrodes. 
In Part V. the relation of the leaf to different modes of exci- 
tation is investigated. As regards electrical excitation the 
results are as foliows:—If a voltaic current is led across one 
lobe by non-polarisable electrodes applied to opposite surfaces 
(the other lobe being led off as in the fundamental experiment) 
a response (excitatory variation) occurs at the moment that the 
current is closed, provided that the strength of the current is 
adequate, and not much more than adequate. No response 
occurs at breaking the current. When a current of more than 
adequate strength is used, and its direction is downwards, the 
response at closing is followed by several others. This effect 
does not happen when the current is directed upwards. To 
evoke a response a current must be much stronger if directed up- 
wards than if directed downwards through the same electrodes. 
Weak currents cease to act when their duration is reduced to 
xiv’; for stronger ones the limit is shorter. Inadequate cur- 
rents, if directed downwards, produce negativity of the upper 
surface, which lasts for several seconds after the current is 
After excitation. 
broken. This effect is limited to the surfaces through which the 
current is led. Its direction shows it is not dependent on polar- 
isation. By opening induction-currents, if their strength does 
not much exceed the limit of adequacy, a leaf may be excited at 
intervals for several hours without failure. Weaker currents 
are more effectual when directed downwards than when directed 
upwards. If two inadequate induction-currents follow one 
another at any interval less than o”*4 and greater than 002, 
they may evoke a response. In this case a response follows the 
second excitation. When a leaf is subjected to a series of induc- 
tion currents at short intervals (3,”) the response occurs after a 
greater or less number of excitations. If the temperature is 
gradually diminished the number is increased by each diminu- 
tion. All of the above statements relating to excitability refer 
to plants kept in a moist atmosphere at 32—35° C. 
From the preceding facts and others which are stated in the 
paper, the author infers (1) that the difference observed between 
different parts of the surface of the leaf are the expressions of 
electromotive forces which have their seat in the living proto- 
plasm of the parenchyma cells. (2) That the second phase of 
the excitatory variation is probably dependent on the diminution 
of turgor of the excited cells, and therefore on the migration of 
liquid; (3) but that no such explanation can possibly be 
accepted of the phenomena of the first phase, the time relations 
of which, particularly its sudden accession and rapid propaga- 
tion, show it to be the analogue of the ‘ negative variation ” or 
‘action current” of animal physiology. 
Zoological Society, January 3.—Prof. W. H. Flower, 
F.R.S., president, in the chair.—Mr. W. A. Forbes exhibited 
and made remarks on the horns of the Prong Buck (Anéslocapra 
americana) lately shed by the specimen living in the Society’s 
Gardens. This was, it is believed, the first instance on record 
of the same individual having shed its horns in captivity in two 
™ 
| ¥an. 12, 1882 
consecutive years.—A communication was read from Prof, © 
Owen, C.B., on Dinornis (Part xxiii.), containing a description 
of Dinornis parvus, a new species of about the size of the Dodo, 
of which a very complete skeleton (now in the British Museum) 
had been lately discovered in a cavern in the province of Nelson, 
New Zealand. —A communication was read from M. L. Taczan- 
owski, C.M.Z.S., containing an account of the birds collected 
by Mr. Stolzmann during his recent journey in North-Eastern 
Peru, with descriptions of some new species. —A communication 
was read from Mr. Martin Jacoby, containing the descriptions 
of three new genera and fourteen new species of Phytophagous 
Coleoptera from various localities.—Mr. Oldfield Thomas read 
a paper on the African Mungooses (Herfestine), in which he 
reduced the described species of this group to nineteen, divisible 
into seven genera, —The Rey. Canon Tristram read the descrip- 
