PLANT RESPONSE 133 



death-spasm occurs, a perfected form of apparatus a 

 ' Death Recorder ' was devised. The death-point at 

 any rate for all the dicotyledonous plants observed and 

 their different organs was found to be almost as definite 

 as a physical constant ; for, using very diverse specimens 

 and methods, the critical temperature is always at or very 

 near 60 C. The death-contraction in the plant is in every 

 respect similar to the same phenomenon in the animal, and 

 is an instance of true excitatory effect. Yet different plants 

 have their characteristic death-curves, and the same species 

 may exhibit variations under changed conditions of age 

 and previous history. Thus when the plant's power of 

 resistance is artificially depressed, whether by poisons or 

 by fatigue, its death-spasm occurs at a temperature 

 often considerably lower even as much as 23. This 

 phenomenon, of course, also shows that the death-spasm is 

 no mere phenomenon of coagulation ; for even if it takes 

 place at 60 or thereabouts, it cannot also happen at 37 C. 



As stated before, there is an electrical spasm corre- 

 sponding to the mechanical spasm at death. The electro- 

 motive force generated at death-temperature is sometimes 

 considerable : Bose shows that in each half of a green 

 pea it may be as high as half a volt. If five hundred 

 peas are suitably arranged in series, the electric pressure 

 will be five hundred volts, which may cause even electrocu- 

 tion of unsuspecting victims. And so Bose drily remarks : 

 ' It is well that the cook does not know the danger she runs 

 in preparing the particular dish ; it is fortunate for her that 

 the peas are not arranged in series ! ' 



All this complex investigation necessarily depended 

 on contriving and adjusting three different systems of 

 apparatus for recording different modes of response, 

 mechanical and electrical. Though the instruments em- 

 ployed were so widely different, yet the responses obtained 

 were found to agree in every important detail. 



Much investigation has been devoted in these books, and 

 also, more recently, to the nature and causes of ' automatic ' 



