I 8 PLANT RESPONSE 



kathode during ' charge,' when the key is pressed. When the 

 key is released, the circuit is ' discharged,' and the current 

 flows in the opposite direction. 



The given point r, is, as has been said, excited by being 

 made kathode at the moment of charge. The immediately 

 succeeding discharge produces no exciting effect, but it wipes 

 off any residual polarisation effect caused by charge. The 

 plant-tissue is thus maintained in as completely normal a 



Fig. 14. Diagram of Connections for Stimulation by Condenser Discharge 



Pressure of key K charges the condenser c through the plant. Release of key 

 brings it in contact with M, discharging the condenser through the plant. 

 L, responding leaflet attached to recording lever by thread s. 



condition as possible. The excitation produced in the plant 

 by current to or from the condenser, I shall, for simplicity, 

 designate as ' stimulation by condenser discharge.' 



In the course of the present chapter we shall study the 

 response of the leaf of Mimosa^ shown by its fall, and also 

 that of other sensitive plants, exhibited by the closure of 

 the leaflets, as in the case of BiopJiytuin scjisitiviivi. One 

 difficulty encountered in obtaining successive responses, in 

 these latter cases, was due to the fact that the responding 



