270 PLANT RESPONSE 



interval between successive sparks was fe of a second. By 

 this means, it was found that increasing fatigue induced a 

 corresponding increase in the latent period of a leaf of 

 Mimosa, from the normal ffo to jVtt °f a second. 



Response of Biophytum. —I shall now proceed to de- 

 scribe effects essentially similar to the last, seen in Biophytum. 

 In order to be able to observe in detail the various responsive 

 peculiarities of the curve, subsequent to stimulation, records 

 were taken in this case on a much slower-moving drum. The 

 record given in fig. 112 shows the mechanical response to 

 stimulation produced by discharge of condenser (capacity -oi 



Fig. 112; Response of Biophytum ; Electrical Stimulus having been 

 Applied at the Pulvinus of the Motile Leaflet 



The thick dot represents the moment of stimulation. 



microfarad, charged to nine volts). The exact moment of 

 stimulation is marked on the record. 



It will be seen that the leaflet begins to respond almost 

 instantaneously. The maximum contraction in this case, 

 being considerably more rapid than in that of Mimosa, is 

 almost attained in the course of half a second. An interest- 

 ing point to be noticed in the record is the flattening of the 

 top of the curve (fig 112). That is to say, the maximum 

 contraction persists for a considerable time before recovery 

 begins. In the present case this lasted for ten seconds. This 

 period varies in different specimens, from a maximum of ten to 

 about two seconds. But in this particular specimen the period 



