APEX TIME OF DESM ODIUM 309 



The latent period of motile leaflet of Desmodium is of the 

 same order. It varies from -4 second to -5 second. 



The Apex Time 



In order to study in detail the time-relations, I took on a 

 fast-moving plate the response of Desmodium leaflet, origin- 

 ally in a state of standstill, to the action of induction-shock. 

 The frequency of oscillation of the recording-plate was once 

 in a second, hence successive dots represent intervals of 



Fig. 153. — Response of Desmodium leaflet originally at standstill. 

 Successive dots at intervals of i second. 



I second. The entire response, consisting of contractile 

 down-movement and subsequent recovery, was accom- 

 plished in the course of 2 minutes and 45 seconds ; the 

 leaflet attained its maximum down or contractile position 

 45 seconds after the application of stimulus. The top of 

 the response-curve is seen to be somewhat flattened, indi- 

 cating a persistent contraction from which recovery takes 

 place slowly. The period of relaxation is much longer, 

 being 120 seconds ; the record in fig. 153 shows recovery 

 which is not quite complete. 



Taking thus a typical case we find that in Desmodium, 



(i) The latent period is -5 second. 



(2) The apex time is 45 seconds. 



(3) The period of relaxation is 120 seconds. 



