254 



COMPARATIVE ELECTRO-PHYSIOLOGY 



attained in a much shorter time that is to say, in about 

 03 second. I give below a table showing the rheotomic 

 observations made on such a leaf at gradually increasing 

 intervals after the exciting shock. It should be remembered 



TABLE OF RHEOTOMIC OBSERVATIONS. 



that the recording galvanometer was un-shunted for -01 

 second, The curve given in fig. 161 has been plotted from 



these results. The maximum 

 electro-motive change took place, 

 as already pointed out, in -03 

 second after the application of 

 stimulus. This curve shows 

 multiple apices, as was also the 

 case, it will be remembered, after 

 a strong mechanical stimulation 

 (cf. fig. 40). This point will be 

 referred to in greater detail in 

 the next chapter. In the course 

 of half a second after the shock, 

 the excitatory electro-motive 

 change had subsided to about 

 one-twelfth of the maximum. 



It has been said that the 

 excitatory current depends for 



Ordinate represents galvanometer its definiteness of direction on 

 deflection; abscissa, time in the physiological anisotropy of 

 hundredths of a second. 



the organ. In those leaves 



in which the physiological differentiation of the upper and 

 lower surfaces is not strongly marked, the differential 



