COxXTEXTS XV 



CHAPTER XII 



EFFECT OF TEMPERATURE 



Temperatures optimum, maximum, and minimum — Diminution of electrical 

 response by cooling — Temporary or permanent abolition of response due 

 to cold — Characteristic differences exhibited by different species- 

 Mechanical response of Biophytinn and autonomous response of 

 Desmodmm arrested by cold — Prolongation of latent period — Diminution 

 of longitudinal mechanical response by cold— Diminution of electrical 

 response of plants by rise of temperature— Similar diminution seen in 

 longitudinal mechanical response — Increase of excitability due to cyclic 

 variation of temperature ......... 159 



CHAPTER XIII 



ON THE DEATH-SPASM IX PLANTS 



Difficulty of determining exact moment of death — Various post-mortem 

 symptoms afford no immediate indication — Ideal methods for determina- 

 tion of death-point — Realised in four different ways : [a) Determination 

 by electrical method— (A) Determination by spasmodic lateral movement 

 at moment of death — Experiments with Mimosa — Death-contraction a 

 true physiological response— Continuity of fatigue and death— Death- 

 point earlier in young tissues — Composite spasmodic movement — (/'') 

 Determination of death-point in tendril of PassiJJora, by sudden move- 

 ment of uncurling— (<r) Determination of death-point by method of volu- 

 metric contraction of hollow organ, causing expulsion of contained water 14S 



CHAPTER XIV 



THE DETERMINATION OF THE CRITICAL POINT OF DEATH 

 BY INVERSION OF THE THERMO-MECHANICAL CURVE 



Death-spasm in anisotropic organ due to differential longitudinal contraction 

 — In radial organ the death-contraction is purely longitudinal — Death- 

 point determined from point of inversion of a thermo-mechanical curve 

 — The complete record thus constitutes a curve of life-and-death, the two 

 being separated by the death-point— Characteristic thermo-mechanical 

 curve as resultant of variation of temperature and variation of length— 

 The necessity of specifying the rate of rise of temperature — The thermo- 

 mechanical curve characterised by sharp and definite inversion at point 

 of death — No inversion of thermo-mechanical curve after death of plant 

 — Death-contraction under heat-rigor in plant analogous to similar 

 phenomenon in animal — -The Morograp/i, a perfected form of apparatus 

 for determining critical point of death — Remarkable identity of thermo- 

 mechanical curves obtained with two similar specimens— Death -point 

 almost as definite as a physical constant — Vanishing of point of inversion 

 with age — Determination of death-point under cold-rigor — Constancy of 

 death-point ........... 159 



