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 

 its definiteness of direction on 

 the physiological anisotropy of 

 the organ. In those leaves 

 in which the physiological differentiation of the upper and 

 lower surfaces is not strongly marked, the differential 



FIG. 161. Response-curve from 

 Rheotomic Observation on Leaf 

 of Nymphcea alba 



Ordinate represents galvanometer 

 deflection ; abscissa, time in 

 hundredths of a second. 



