128 LIFE AND WORK OF SIR JAGADIS C. BOSE 



which has become increasingly predominant. The essen- 

 tial problem is thus stated : Is the plant a mysterious 

 entity, with regard to whose working no law can be 

 definitely predicated ? Or can it be interpreted as a 

 machine i.e. as transforming the energy supplied 

 to it in ways more or less capable of explanation ? 

 So diverse are its movements that the first hypothesis 

 has often seemed the only one. For light may induce 

 sometimes positive curvature, sometimes negative ; gravi- 

 tation induces one movement in the root and the 

 opposite in the shoot, and so on : whence it appeared to 

 many, even to evolutionists, as if the organism had become 

 endowed with various specific sensibilities for its own 

 advantage, but that a consistent physico-chemical explana- 

 tion of its movements was out of the question, However, 

 the thesis is here clearly affirmed, and justified in detail, that 

 ' the plant may nevertheless be regarded as a machine ; 

 and that its movements of response to external stimuli, 

 though apparently so various, are ultimately reducible to 

 a fundamental unity of reaction. This demonstration has 

 been the object of the present work, and not that treatment 

 of known aspects of plant-movements which is to be found 

 detailed, together with the history of the subject, in standard 

 books of reference on Vegetable Physiology.' 



Of this large thesis the first chapter is a model of explicit 

 statement. ' The plant, like a machine, responds either to 

 the impact of external forces, or to energy latent within. 

 As the working efficiency of an engine is exhibited by 

 indicator-diagrams, so the physiological efficiency of a 

 living machine may be inferred from the character of its 

 pulse-records/ The making of the records, and the mode 

 of exhibiting them during their progress (even to the largest 

 audiences), are explained and clearly figured ; this ' Optical 

 Pulse-Recorder ' may therefore here be figured (Fig. 7), as at 

 once simple and convincing. The apparatus consists of a 

 twin drum, over which is wrapped a band of paper to serve 

 as the recording surface. The drums are kept revolving by 



