RHYTHMIC RESPONSE IN PLANT AND ANIMAL 345 



gives a single response to a single stimulus, or if the stimulus 

 be sufficiently strong, a multiple series of rhythmic responses. 

 In the plant Desmodium, under favourable tonic conditions 

 we observe automatic movements ; but when under less 

 favourable circumstances, as for instance owing to the 

 unfavourable season, it is brought to a state of standstill, it 

 gives a single response to a single stimulus. When the 

 stimulus, however, is strong, we have seen that it gives rise to 

 a multiple series of responses, in a manner precisely like that 

 of Biophytum under similar circumstances. It will thus be 

 seen that Biophytum in its ordinary condition may be 

 regarded as equivalent to Desmodium in a state of standstill. 

 Similarities, in their fundamental characteristics, of 

 rhythmic tissues, animal and vegetable : (i) In responses. — 

 In the matter of response, we have found that the rhythmic 

 automatic movements of cardiac muscle are repeated in 

 Desmodium under ordinary tonic conditions, and in Biophytum 

 under exceptionally favourable circumstances. In a state of 

 standstill, all three give a single response to a single moderate 

 stimulus, and a multiple series of rhythmic responses to a 

 sufficiently strong stimulus. The following tabular statement 

 exhibits this parallelism in a concise form : 



Tabular Statement showing Similarities in the Responses of 

 Rhythmic Animal and Vegetable Tissues 



