60 



Anniversary Meeting. [Nov. 30, 



response to mechanical, chemical, or electric stimuli. In 1873, 

 Dr. Sanderson showed ns in this meeting room, that the closing of the 

 laminse of the leaf of Dioncea is preceded by a preliminary state of 

 excitement, and is attended with a change in the electric conditions of 

 the leaf ; and this so closely resembled the change which attends the 

 excitation of the excitable tissues of animals, that he did not hesitate 

 to identify the two phenomena. 



This remarkable discovery immediately directed the attention of 

 two German observers to the electromotive properties of plants, one, 

 Dr. Knnkel, in the Laboratory of Professor Sachs; the other Pro- 

 fessor Munk, in that of the University of Berlin. 



Professor Munk, whose researches are of much the greater scope 

 and importance, took as his point of departure Dr. Burdon Sanderson's 

 discovery. The leading conclusion to which he arrived was, that in 

 Dioncea each of the oblong cells of the parenchyma is endowed with 

 electromotive properties, which correspond with those of the " muscle- 

 cylinder " of animals ; with this exception, that whereas in the muscle- 

 cylinder the ends are negative to the central zone, in the vegetable cell 

 they are positive ; and he endeavours to prove, that according to this 

 theory, all the complicated electromotive phenomena which had been 

 observed, could be shown to be attributable to the peculiar arrange- 

 ment of the leaf-cells. 



During the last two summers Dr. Burdon Sanderson has been 

 engaged in endeavouring to discover the true relations which subsist 

 between the electrical disturbance, followed by the shutting of the 

 leaf-valves of Dioncea and the latent change of protoplasm which 

 precedes this operation. He has found that though the mechanism 

 of the change of form of the excitable parenchyma which causes 

 the contraction is entirely different from that of muscular contraction, 

 yet that the correspondence between the exciting process in the animal 

 tissues, and what represents this in plant tissues appears to be more 

 complete the more carefully the comparison is made; and that 

 whether the stimulus be mechanical, thermal, or electrical, its effects 

 correspond in each case. Again, the excitation is propagated from 

 the point of excitation to distant points in the order of their remoteness, 

 and the degree to which the structure is excited depends upon its 

 temperature. Notwithstanding, however, the striking analogies be- 

 tween the electrical properties of the cells of Dioncea and of muscle- 

 cylinders, Dr. Burdon Sanderson is wholly unable to admit with 

 Professor Munk that these structures are in this respect comparable. 



In Morphological Botany attention has been especially directed of 

 late to the complete life-history of the lower order of Cryptogams, 

 since this is seen to be more and more an indispensable preliminary to 

 any attempt at their correct classification. 



