380 



Sir J. C. Bose and Mr. G. Das. 



growth. I also give a record (fig. 8), which shows in an identical specimen 

 (1) an acceleration of growth under indirect, and (2) a retardation of growth 

 under direct stimulation.. 



Fia. 8. — Efiect of indirect and direct stimulation on growth, (t) shows application of 

 indirect stimulus with consequent acceleration of growth : application of direct 

 stimulus at ( X ) induces contraction and subsequent retardation of rate of growth. 



Table II. — Accelerating Effect of Indirect Stimulation (Crinvm). 



Specimen. 



Rate of growth. 









"21 fi per sec. 

 3 -26 „ „ 



I 



After indirect stimulation 







0-25 „ „ 



II II 



After indirect stimulation 



0-3 „ „ 



From the above results it will be seen that the effect of stimulus is modified 

 by its point of application. 



Hence we arrive at the following laws of direct and indirect stimulation*: — 



1. Direct Stimulation — 



The effect is contraction, diminution of turgor, negative mechanical and 

 electrical response, negative variation (retardation) of the rate of growth. 



2. Indirect Stimulation — 



(a) The effect of feeble stimulus is expansion, increase of turgor, 

 positive mechanical and electrical response, positive variation (acceleration) 

 of rate of growth. 



(&) The effect of prolonged application of stimulus of moderate intensity 

 is a diphasic response, positive mechanical or electrical response followed 

 by the negative ; an acceleration, followed by a retardation of growth. If 

 the intervening tissue be highly conducting, the transient positive effect 

 becomes masked by the predominant negative. 



* Gf. ' Plant Eesponse,' p. 535 ; ' Comparative Electro-physiology,' p. 64 ; ' Irritability 

 of Plants,' p. 196. 



