CHAPTER XIII 



ON THE DEATH-SPASM IN PLANTS 



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

 afford no immediate indication — Ideal methods for determination of death- 

 point — Realised in four different ways : {a) Determination by electrical method 

 — (b) 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 — Com- 

 posite spasmodic movement — {b') Determination of death-point in tendril of 

 Passiflora, by sudden movement of uncurling— (c) Determination of death- 

 point by method of volumetric contraction of hollow organ, causing expulsion 

 of contained water. 



It is known that when the temperature to which it is 

 subjected is raised above a certain maximum, a plant is 

 killed. But it is very difficult to determine at what exact 

 temperature this takes place. One reason of the difficulty 

 lies in the fact that hitherto a sure criterion of death, which 

 would give an immediate and reliable indication of its occur- 

 rence, has not been generally available. Its various symptoms, 

 such as drooping, withering, discoloration, and the escape of 

 coloured cell-sap, do not manifest themselves at the moment 

 of death, but at some time indeterminately later. Even 

 when a plant has been subjected to a temperature in excess 

 of the fatal degree, it continues to appear fresh and living, 

 and it is not till after some greater or less interval that the 

 death-symptoms are seen. Various investigators have taken 

 up different indications as the criteria of death, and this fact 

 accounts for discordance in the results, which would already 

 have been sufficiently uncertain even had a common standard 

 been decided upon. 



Exact methods of determination of death-point. -A 

 good method for the determination of the death-point would 



