2 
PROFESSOR B. SANDERSON ON THE ELECTROMOTIVE 
observer. This aid I have received from Mr. Page, to whose technical skill and 
ingenuity in overcoming difficulties, whatever success may have been attained in the 
experimental part of the enquiry, is largely due. 
I have to express my great indebtedness to the Director of Kew Gardens, Sir Joseph 
Hooker, and to the Assistant Director, Professor Thiselton Dyer, for the invariable 
kindness with which they have placed the resources of the Royal Gardens at my 
disposal. 
Since 1873 several researches have been published in Germany relating to the 
excitatory process in Dionsea, or more generally to plant excitability. In 1876 an 
elaborate work appeared in Berlin by Professor Munk, of which the aim was to 
acquire “ a more exact knowledge of the leaf of Dionsea in its electrical relations; ” 
and in addition two important experimental papers by Dr. Kunkel relating chiefly 
to Mimosa have been lately- published in vol. xxv. of Pfluger’s Archiv, under 
the title “Electrical Researches Relating to Animal and Vegetable Structures.” For 
the purpose of deriving from them valuable aid, no less than for that of criticising 
the observations and conclusions of their authors, it will be necessary to examine 
these papers carefully. I therefore propose to devote an introductory section to this 
obj ect. 
PART I. 
Examination of the Recent Researches of Professor Munk and of Dr. Kunkel 
on Plant Electricity. 
I. Summary of Professor Munk’s Paper .*—The introduction (§ l) begins by 
referring to the discovery, made by myself in 1873, that the leaf of Dionsea is 
endowed with electromotive activity resembling that of muscle, and that when the 
leaf contracts a negative variation occurs. He states that his attention was first 
directed to Dionsea in November, 1873, and that, in consequence, he made experiments 
in 1874 and 1875, using about 100 leaves, none of which wmre detached from the 
plants to which they belonged. 
§ 2 relates to the distribution of electrical tension on the surface of the leaf. After 
confirming the observations recorded in my first communication to the Royal Society, 
that in general when the Dionsea leaf is led off by the opposite ends of the outer 
surface of the midrib, the end furthest from the leaf stalk (distal) is found to be posi¬ 
tive to the other endt, he states (l) that the most positive point is not the distal end 
of the midrib, but the point corresponding to the junction of its middle with its distal 
third, (p. 37) to which point, though both ends are negative, the petiole end is twice 
* Die elektrisclieii und Bewegungs-Erscheinungen am Blatte der Dion&a Muscipula, von Dr. Hermann 
Munk, a. o. Professor an der Universitat zu Berlin. Leipzig, 1876. Aus Reichert’s und du Bois- 
Reymond’s ArcLiv fur Anatomie, &c., 1876, besonders abgedruckfc. 
f “ Herrn Sanderson’s Angabe ist leicbt zu bestatigen : man findet in der That regelmassig zwischen 
jenen Blattenden, nach unserer Bezeichnungsweise, einen aufsteigenden Strom.” 
