130 LIFE AND WORK OF SIR JAGADIS C. BOSE 



Again it is shown that agencies which depress the 

 physiological condition of a tissue also depress its 

 pulse of response (and conversely) ; and this response 

 ceases with death, just as does that shown in the 

 indicator-diagram with the stoppage of the machine. 

 Starting again with the muscle-curve so long familiar to 

 animal physiologists, analogous curves are now for the first 

 time obtained for the contractions of ordinary plants : not 

 only those of the sensitive stamens of various composites, 

 and the leaves of the sensitive plants, but also of ordinary 

 leaves. The filaments which make up the corona or 

 ' glory ' of the passion-flower were found to give an 

 excitatory contraction of great magnitude, . up to as much 

 as 20 per cent, of their length. This is only an extreme 

 case : the pistil and style and stamen of the flower exhibit 

 contraction. The phenomenon, of course, varies with 

 the nature of the tissue, since the thin cellulose walls of 

 young cells may acquire many later thickenings and harden- 

 ings, which are often of great mechanical strength and 

 resistance. Turgidity too is an important and interestingly 

 variable internal factor ; and age, season, temperature, 

 and other factors have all to be reckoned with. 



The modification of response exhibited by given plants 

 and their organs under various conditions is next copiously 

 experimented on. Response is not merely uniform : it may 

 show progressive increase the ' staircase effect ' of animal 

 muscle. Nor is fatigue merely a muscular phenomenon. 

 Plant-records also amply exhibit it ; for these readily 

 become ' tired out ' by long-continued previous stimula- 

 tion. The accompanying tracings (Figs. 8 and 9), taken 

 by his automatic recorders, show how the successive re- 

 sponses, under different conditions of experiment, undergo 

 a ' staircase ' enhancement or a ' fatigue ' depression. 

 Indeed some of the more intricate phenomena of fatigue, 

 nowadays being so actively studied, alike for educational, 

 athletic and industrial purposes, are seen not to be without 



