PLANT SCRIPTS 3 



as that in the animal ? Is there to be found in plants any 

 tissue that might twitch persistently, like the cardiac tissue 

 of the animal ? If so, are these rhythmic pulsations charac- 

 teristically similar ? Is there, again, any general resem- 

 blance between responsive actions in plant and animal? 

 Going deeper, since the same protoplasmic basis underlies 

 them both, are these reactions to be regarded as essentially 

 the same, though different in degree ? If this last were 

 true, then since the simpler explains the more complex, 

 might not the physiological reactions of the plant be expected 

 to elucidate many of the obscurities in the similar reactions 

 of animal tissues ? 



We return, then, to the question, Is the plant capable 

 of furnishing any such responsive indications as we have 

 supposed ? I have shown elsewhere that all plants give 

 response to impinging stimulus by a definite electrical 

 change, J which can be recorded by means of suitable 

 apparatus. For the purpose of the present work, however, 

 it will be convenient to employ the more conspicuous motile 

 indications afforded by certain plants, pre-eminent amongst 

 which is Mimosa pudica. 



The most prominent motile organ in Mimosa consists of 

 a mass of tissue known as the pulvinus, at the joint or arti- 

 culation of the primary leaf-stalk. The swollen mass on the 

 lower side of this organ is very conspicuous. Under excita- 

 tion the parenchyma, in this more effective lower half, 

 undergoes ' contraction,' in consequence of which there is 

 a fall of the leaf. This sudden movement constitutes 

 the mechanical response of the leaf to the impinging 

 stimulus, just as the contractile movement of a muscle in 

 similar circumstances forms its characteristic mechanical 

 response. 



Digressing for a moment to consider the phenomenon 

 of excitatory contractions in general, it may be said that 

 our present knowledge is not complete as to the minutice 



1 Bose : Friday Evening Discourse — Royal Institution, May 1901 ; 

 Comparative ElectrO'Physiology, Longman's, London, 1907. 



B 2 



