230 RESEARCHES ON IRRITABILITY OF PLANTS 



lay in the value of the minimally effective e.m.f., which in 

 less excitable specimens was sometimes as high as 8 volts. 



Table XII. — Effect of Feeble Current on Pulvinus of Mimosa 

 E.M.F. = 4 volts ; current = 4 micro-amperes 



Effect of moderate current. — Under an increasing e.m.f. 

 the characteristic polar effects seen in the pulvinus of 

 Mimosa are, as in other cases, transformed into those of 



Fig. 115. — Under 8 volts excitation at kathode-make; under 

 12 volts excitation at kathode-make and anode-break. 



Type II. Thus in a particular case the e.m.f. applied was 

 10 volts, the resulting current being 8 micro-amperes. In 

 carrying the experiment through the usual cycle of direct 

 and reverse currents it was found that the kathode excited 

 at make, and the anode at break. In fig. 115 are shown 

 a series of records given by a different leaf under kathode- 

 make, kathode-break, anode-make, and anode-break. It 

 will be seen that under a feeble current, due to an e.m.f. 



