434 



On the Leaf of Dionsea muscipula. [Dec. 14^ 



return occupies about the same time, so that we may regard two seconds 

 as the duration of the whole process of latent stimulation. We have 

 already seen that the mechanical effect of excitation, viz. the change of 

 form of the leaf, does not begin until at least two seconds and a half after 

 the excitation ; consequently it may be concluded that in every instance 

 the electrical effect is entirely over before the mechanical effect begins. 



Section 6. — Influence of Temperature. 



The conspicuous analogies which, throughout our investigations, have 

 presented themselves between the phenomena of excitation in the leaf 

 and those which occur in nerve and muscle, rendered it of great import- 

 ance to ascertain whether those physical agents which are known to exer- 

 cise a decisive influence on the excitation process in animal tissue have 

 a similar influence on that in the plant. This subject we propose to 

 investigate more fully next season. In the mean time we submit the 

 results of two experiments, either of which would be sufficient to show 

 that the influence of temperature on the plant corresponds completely 

 with what is known as to its effect on the contractile tissue of animals. 



In each case a leaf, which for this purpose was necessarily detached 

 from the plant, was investigated at the ordinary temperature of a room, 

 then placed for twenty minutes in a chamber warmed to 45 C, and then 

 cooled by placing a block of ice in its neighbourhood. The results of the 

 chronometrical comparison of its condition, under these circumstances, 

 are as follows : — 



Table Y. 

 Time, in seconds, after excitation of 





Beginning 

 of 



excursion. 



Maximum 

 of 



excursion. 



End of 

 excursion. 



Expt. 1. 



^Leaf at ordinary teniperature, 1 



18°-20° C J 



After 10 minutes in chamber 



0-22 



0-17 

 0-12 

 0-29 



0-86 



0-51 

 0-42 

 0-92 



Not observed. 



5 J J? 



Expt. 2. 



f Leaf at ordinary temperature . . . 

 After 20 minutes in chamber 



0-23 

 0-11 

 0-44 

 0-44 



1-46 



0- 79 



1- 48 

 1-68 



2- 2 



1- 37 



3- 1 



2- 94 



