188 COMPARATIVE ELECTRO-PHYSIOLOGY 



to be diminished, since the amplitude of response was con- 

 siderably enhanced. That the general excitability of the 

 plant was not increased by the lowering of temperature, 

 is seen from the fact that the frequency of pulsation was 

 reduced on cooling to about two-thirds of its original value. 



The diminution of response with rising temperature may 

 thus be due to an increase of internal energy, which tends 



FIG. 126. Photographic Records of Autonomous Pulsations in Des- 

 modium, showing Increase of Amplitude and Decrease of Frequency, 

 with Lowering of Temperature 



The pulsations to the left were recorded at the ordinary temperature of 

 the room, 29 C. Those to the right, when the temperature had been 

 lowered to 25 C. 



to cause antagonistic expansion and consequent galvano- 

 metric positivity. This view finds support from the records 

 seen in figs. 129 and 133, given in the next chapter. The 

 first of these (fig. 129) shows the expansion, with consequent 

 physical elongation, of the filament of Passiflora under a 

 rising temperature. In the second (fig. 133) is seen the in- 

 creasing galvanometric positivity of a specimen of Amaranth 

 under similar circumstances. 



It is now clear that when the temperature of the tissue 



