150 PLANT RESPONSE 



example, the specimens tested were radishes, and the experi- 

 ment was conducted during the winter season in England. 

 It would appear from the results given, that in these six cases 

 response begins to be abolished at temperatures varying from 

 35° to 55° C. It will be shown later that the death-point 

 depends on the season, being a few degrees lower in winter 

 than in summer. 



Table showing Effect of High Temperature in Abolition of 

 Response and Death of Plant 



Galvanometric re- I Galvanometric re- 



Teinperature sponse of specimen Temperature sponse of specimen 



at given temp. at given temp. 



17 C 70 dns. (17° C 80 dns. 



(1) i (4) 



53° C 4 „ (55° C ., 



17 C 160 „ (17 C 40 



(5) 



53° C 1 „ l6o^ C o 



17 C 100 ,, (17° C 60 



(6) 



50" C 2 „ (ss° C o 



(b) By observation of the spasmodic movement of lateral 

 response. — I now turn to the second of the four methods 

 which I have named, that in which a spasmodic lateral 

 movement is looked for, in a dorsi-ventral or anisotropic 

 organ, at the moment of death. It has been shown that 

 when an electric shock of moderate intensity is applied 

 to an anisotropic organ, say the leaf of Mimosa, response 

 occurs, in consequence of molecular derangement, and recovery 

 takes place on restoration of molecular equilibrium. If the 

 shock, however, be excessive, response occurs, it is true, 

 but there is no subsequent recovery, owing to the fact 

 that the molecular derangement has passed beyond the 

 point where restoration was possible. There is thus a per- 

 manent, irreversible ' set,' and the organ is now said to be 

 killed. 



At death, then, a sudden irreversible molecular derange- 



