MULTIPLE RESPONSE 29 1 



circumstances, behaving in either of these ways ; that is 

 to say, giving ordinary response, or exhibiting automatic 

 movements. 



Continuity of multiple and automatic response. — If there 

 be thus no real breach of continuity between multiply and 

 automatically responding plants, it should be possible, under 

 suitable circumstances, to obtain from such a characteristi- 

 cally automatic plant as Desmodiuni all those peculiarities of 

 responsive indication which were found in Biophytum. The 

 latter, it will be remembered, under the condition of over- 

 excitability, consequent on the absorption of abundance of 

 energy of heat and light, became converted from an ordinarily 

 responding into an automatically responding plant. Con- 

 versely we might expect Desnwdium, under the opposite 

 circumstances, to pass from the condition of giving automatic 

 to that of giving ordinary response. 



This inference I have been able to verify, for I succeeded 

 in obtaining the requisite conditions for converting the auto- 

 matically responding Desmodiuni into an ordinarily responding 

 plant, in three different ways : firstly, by artificially reducing 

 the absorbed energy of the plant, under cautious cooling, care 

 being taken that this did not produce permanent cold-rigor ; 

 secondly, by keeping a plant for some days in a dark room, 

 at uniform temperature ; and thirdly, by selecting a plant for 

 experiment in the most unfavourable season of the year — that 

 is to say, in the winter, when it was already exhausted by 

 flowering. It will be seen that the principle adopted in each 

 of these cases consisted in depriving the plant of its excess of 

 energy. The third method was the most satisfactory of all, 

 since the leaflets were in a state of natural standstill. In 

 every instance, the automatic movements of the leaflets came 

 to a stop, and the motile organ was reduced, as will be shown, 

 to the ordinarily responding condition. In choosing the 

 leaflets for experiment, it must be remembered that their 

 sensitiveness is liable to disappear with age. In Biophytiini, 

 for example, very old leaflets show no response. In experi- 

 menting, therefore, on leaflets of Dcsuiodium which have been 



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