278 PROF. Je C. BOSE ON ELECTRIC RESPONSE IN 
of injury. This may be expressed in another way by saying 
that stimulus gives rise to an “ action current,” the direction of 
which is from the more responsive or excitable A to the less 
responsive B *. 
An experiment with plants will presently be described which 
will exhibit the responsive negative variation. 
For exhibiting electric response, it is preferable to use a 
non-electrical form of stimulus, for there is then a certainty that 
the observed electric variation is solely due to the action of 
stimulus, and not, as might be the case with the electric mode 
of stimulation, to mere escape of stimulating current through 
the tissue. For this reason the mechanical form of stimulation 
is the most suitable. 
I find that all parts of the living plant give electric response 
to a greater or less extent. In favourable cases, we may have 
an electromotive variation as high as ‘1 volt. It must, however, 
be remembered that the response, being a function of physiological 
activity of the plant, is liable to undergo changes in different 
seasons of the year. Each plant has its particular season of 
maximum sensitiveness. The leaf-stalk of horse-chestnut, for 
example, exhibits fairly strong response in spring and summer, 
but on the approach of autumn the responsive power undergoes 
a marked diminution. I give here a list of specimens which 
will be found to exhibit fairly strong response. 
Root.—Carrot (Daucus Carota), radish (Raphanus 
sativus). 
Stem.—Geranium (Pelargonium), vine (Vitis vinifera). 
Leaf-stalk.—H orse-chestnut(Zsculus Hippocastanum),turnip 
(Brassica Napus), cauliflower (Brassica oleracea), 
celery (Apium graveolens), Eucharis lily. 
Flower-stalk.—Arum lily. 
Fruit.—Egeg-plant (Solanum Melongena). 
* It must be remembered that ‘negative variation” presupposes at 
antecedent current of injury in reference to which the “action current” is 
negative. It will be shown that a responsive current may be obtained without 
any antecedent injury ; negative variation has then no meaning. Again, the 
myury current—the current of reference—sometimes has its sign reversed. 
Chere is thus a likelihood of confusion arising from the reversal of direction 
of current of injury. Current of injury in plants due to cross sectional cuts 
often undergoes reversal. No confusion can, however, arise if the current of 
response is indicated as from the more excitable to the less excitable. 
