REVIEW OF RESPONSE, SIMPLE AND MULTIPLE 72 1 



The sum total of the energy derived by the plant from 

 the various stimuli of its environment determines what is 

 known as its tonic condition. 



Continuity of multiple and autonomous responses. — 

 There is no line of demarcation between the phenomena of 

 multiple and autonomous response. When the latent or 

 internal energy of the plant is above par, it finds expression 

 in the form of multiple response, which is apparently auto- 

 matic. Taking the typical case of a multiply-responding 

 plant which is furnished by BiopJiytum, we find, on supplying 

 it with excess of energy, by maintaining it at the tempera- 

 ture of say 35 C, and thus exalting its tonic condition, that 

 it displays autonomous response. Conversely, when the 

 tonic condition of an autonomously responding plant, such 

 as Desmodium, is in any way reduced, by reason of low tem- 

 perature, unfavourable season, or other circumstances, it 

 becomes converted into an ordinarily-responding plant like 

 Biopliytum. A single moderate stimulus now gives rise to a 

 single response, and a strong stimulus to multiple responses. 



It is in accordance with this, that a Desmodium leaflet in 

 a state of temporary standstill has its multiple or autonomous 

 response renewed by any circumstance, or combination of 

 circumstances, which sufficiently enhances the internal energy 

 of the plant. Amongst such circumstances are: (1) The 

 action of light ; (2) favourable temperature ; (3) the presence 

 of stimulating chemical substances ; (4) an increase of internal 

 hydrostatic pressure. 



The energy which expresses itself in pulsatory move- 

 ments, then, may be derived by the plant either directly 

 from immediate external sources ; or from the excess of such 

 energy already accumulated and held latent in the tissue, 

 aided by the incidence of external stimulation ; or from an 

 excessive accumulation of such latent energy alone. Thus 

 there is, strictly speaking, no such thing as automatism, for 

 only when acted upon by stimulus can a living tissue give 

 responsive indications. The impact of an external stimulus 

 may give rise to immediate response, or it may be held 



3 A 



