POLAR EFFECTS OF MODERATE CURRENTS 231 



of 8 volts, the reactions are those characteristic of Type I. 



But when the acting current was increased by applying the 



higher e.m.f. of 12 volts, the responsive characteristics, as 



was to be expected, changed to those of Type II. Whereas 



under feeble current the kathode alone had excited at 



make, now under moderate current excitation occurred 



at both kathode-make and anode-break. 



These distinctive effects of the moderate current were 



obtained with no fewer than fifteen different specimens in 



spring, and were thus shown to be characteristic of plants in 



normal condition. Later in the year, however, seasonal 



changes were seen to induce certain modifications of the 



polar effects ; these will be fully described in another 



chapter. 



Table XIII.— Effect of Moderate Currents on Mimosa 

 e.m.f. = 10 volts ; current = 8 micro-amperes 



It will now be advisable to recapitulate the results 

 described in the present chapter, in order to show how 

 universal these phenomena are. I will first give a tabular 

 statement of the effect of feeble current : — 



Table XIV. — Effect of Feeble Current on Various Specimens 

 of Sensitive Plants 



Type I. — Excitation formula Km 



