34 
PROFESSOR B. SANDERSON ON THE ELECTROMOTIVE 
led to the conclusion that inequality of response has a much larger share in its pro¬ 
duction than loss of time. Ground for this conclusion is to he sought, as regards each 
particular case in which a symmetrically led off leaf acts unsymmetrically, in the 
observation that each of its two lobes when, separately and successively tested shows 
the same inequality. Unfortunately, the nature of the case did not present itself in 
its true relations until too late to do this in a sufficient number of cases, but I have 
abundant evidence that in general the electrical reactions of the two lobes of a leaf 
are unequal. 
Fig. 12. 
Diagram intended to illustrate the relations of the first phase of the excitatory variation when 
the leaf is led oil by symmetrical contacts on the under surface. 
In observations on symmetrically led off leaves the electrodes may be applied either 
to the internal or the external surface. 
Symmetrical contacts on the internal surface of the leaf between the two marginal 
sensitive hairs. —In order to determine, if possible, the general character of the varia¬ 
tion in this form of experiment, four observations were made in succession with the 
electrometer. The leaves used were led off by symmetrical contacts between marginal 
