THE SLEEP OF PLANTS 203 



four hours. In this way it was found (Fig. 26) that the 

 plant is a late riser, waking up very gradually and very 

 slowly ; it becomes fully alert by noon, remaining so until 

 evening. It is, however, quite awake until midnight. It 

 then begins to grow somewhat lethargic, but does not lose 

 its sensibility until the early hours of the morning, when its 

 excitability disappears, and the plant ceases to give any 

 answer. 



FIG. 26. Diurnal record showing variation of sensibility of Mimosa from 

 5 P.M. to 5 P.M. next day. 



The anomalies and intricacies of plant-movements, 

 though so baffling, served only, as we have seen, to spur 

 Bose to renewed efforts. As regards the possibility of 

 unravelling the complexity, he spoke with confidence : 



The extent of our range of investigation is limited ultimately 

 by our power of detecting movement and measuring the rate 

 of movement, that is to say in measurements of length and time. 

 I have shown elsewhere how the employment of my Resonant 

 Recorder enables us to measure time within a thousandth part 

 of a second. We are, on the other hand, able by means of 

 the Crescographic amplification to obtain records of movements 

 magnified a million times. These possibilities and increasing 

 refinement in our experimental methods cannot but lead to 

 important advances towards a deeper understanding of the 

 physiological reactions in living organisms. 



