TEMPERATURE AND AUTONOMOUS RESPONSES 341 



Fig. 143. Photographic 

 Record of Cyclic Group- 

 ings in Autonomous Pul- 

 sations of Desmodium, 

 showing Sub-pulses 



seen in fig. 140, where successive pulsations of the same 

 leaflet, at first apparently continuous, are made to exhibit the 

 sub-pulses with growing distinctness, as the period becomes 

 progressively slowed down by cooling. 

 First we are enabled to observe the 

 sub-pulses during the up movement, 

 and afterwards during the down move- 

 ment also. I give another photo- 

 graphic record also (fig. 143), in which 

 these subsidiary pulses are seen at both 

 the ' systole ' and ' diastole ' (see also 

 fig. 175). Arguing from analogy, 

 therefore, it becomes highly probable 

 that any single pulsation of the heart 

 also may be made up of similar dis- 

 crete and constituent elements. 



While dealing with this question, it must be borne in 

 mind that in each case the contractile organ as a whole is 

 made up of a mass of in- 

 dividually contractile ele- 

 ments, the sum of whose 

 separate and additive ac- 

 tions it is which is seen 

 as a single contraction and 

 expansion of the whole 

 organ. Thus, in Desmo- 

 dium for example, a single 

 pulsation of the motile 

 organ is made up of sub- 

 sidiary pulselets. The 

 unit-pulses, again, may 

 themselves be grouped in 

 larger systems, either as 

 the alternate waxings and 

 wanings seen in periodic 

 groupings (figs. 143 and 149), or in those periodicities of 

 the order of an hour or so, which the plant sometimes 



Fig. 144. Photographic Record of Auto- 

 nomous Pulsation of Desmodium, 

 showing Hourly Period 

 [Speed of drum = 5 cm. in one hour.] 



