802 REPORT— 1902. 



4. Report on the Eespiration of Plants. — See Reports, p. 472. 



5. Report on the Cyanophycece. — See Reports, p. 473. 



6. Report on the Collection and Preservation of Botanical Photographs. 



See Reports, p. 471. 



7, Exhibition of some Characteristic Australian Plants, 

 By Thomas Steel. 



FRIDAY, SEPTEMBER 12. 



The following Papers were read : — 



1. Electric Resjmnse of Ordinary Plants under Mechanical Stimulus.^ 

 By Professor Jagadis Chundee Bose, M.A., D.Sc. 



Electric response has been found by Burdon Sanderson, Munck, and others to 

 occur in sensitive plants. The present investig'ation was directed to find whether 

 these responses were confined to plants which exhibit such remarkable movements, 

 and whether they could not also be obtained from ordinary plants where visible 

 movements are completely absent. The inquiry had the further important object 

 of determining whether throughout the whole range of response phenomena a 

 parallelism iu every detail could be demonstrated between the animal and 

 vegetable. 



Method of experiment. — For exhibition of electric response a non-electrical 

 form of stimulus is preferable. A mechanical tapper gives isolated or superposed 

 stimuli. This form of stimulation labours under certain disadvantages : there is 

 an unknown loss of energy due to rebound ; the plant subjected to repeated blows 

 is liable to be injured, and this might give rise to variation in the successive 

 responses, A more perfect method of stimulation, i.e., of vibration, has been 

 devised by me. The intensity of stimulation is found to depend on the amplitude 

 of vibration. In order to maintain the efiective intensity of stimulus constant it 

 is necessary (1) to maintain the vibration amplitude constant, (2') the period of 

 vibration constant. 



As regards the obtaining of response the method of injury or negative varia- 

 tion may be employed. But a far more perfect plan has been devised by me — that 

 of block. 



The advantages of this method are : (1) The response is obtained under per- 

 fectly normal conditions, the plant being left intact ; (2) every experiment may be 

 duplicated by corroborative reversal experiment. Many investigations which can- 

 not be attempted by the method of inj ury can be easily carried out by the method 

 of block. 



As regards the record of responses the following device is very perfect, and 

 enables demonstration before a large audience. Twin aluminium cylinders are 

 kept revolving at a uniform rate by clockwork, an endless band of paper passing 

 over the cylinders. The moving galvanometer spot of light is at right angles to the 

 motion of the recording paper and is followed with a pen. 



' For a more complete account see the following : Bose, • Response of Inorganic 

 Matter to Stimulus' (Friday Evening Discourse, Royal Institution, May 1901); 

 ' Electrical Response in Ordinary Plants under Mechanical Stimulus ' {Journal 

 Linnean Society, March 1902) ; Response in the Liviiig and Non-living (Longmans, 

 Green, & Co.). " 



