286 



PLANT RKSPONSE 



rapid pulsations, and afterwards slow down (fig. 118). And 

 finally we may have any combination of these (figs. 119 and 

 120). 



Fig. 119. 



Multiple Response in Biophytuni, showing Cyclic Groupings 

 of Amplitude and Period 



These cyclic changes of amplitude and period are seen in 

 all types of rhythmic multiple responses, of which I shall 

 show that the autonomous responses of Desmodium and the 

 growth-responses of all plants are only special cases. These 

 characteristics are seen not only in 

 the rhythmic responses of vegetable, 

 but also in those of animal, tissues. 

 The cause of the latter is still regarded 

 as very obscure. Hence the study 

 of similar phenomena in plants, under 

 simpler conditions, may be expected 

 to throw much light on the subject. 



How striking, even in their more 

 intricate details, are the similarities 

 between multiple responses in plant 

 and animal, will be shown in the next 

 three chapters. For the present I 

 shall confine myself to the considera- 

 tion of two of the most obscure 

 instances in animal tissues, and 

 be paralleled in the case of the 



Fig. 120. Multiple Re- 

 sponse in Biophytinu, 

 snowing Cyclic Group- 

 ings 



shall show them to 

 vegetable. 



Recurrent visual impulses. — It is known that when we 

 look for some time at a strongly illuminated object and after- 

 wards close the eyes, we see the same image repeating itself 

 many times in succession ; and of this phenomenon, so far 



