CHAPTER L 



REVIEW OF RESPONSE, SIMPLE AND MULTIPLE 



Responsive contraction — Kunchangraphic records— Direct and indirect effects of 

 stimulation— Various forms of responsive expression; (a) Lateral motile 

 response by differential contraction; (d) Suctional response; (c) Growth- 

 response ; (d) Torsional response ; (e) Death response ; {/) Thermographs of 

 regional death ; {g) Electrical response— Different types of response : {a) 

 Uniform response ; {b) Fatigue ; (c) Staircase response— Excitability- 

 Conductivity— Polar effects of currents— Multiple response— Continuity of 

 multiple and autonomous responses — The ascent of sap. 



We have now studied in detail the manner in which a plant 

 reacts to the varied forces of its environment, and although 

 its response to them finds modes of expression which appear 

 highly diverse, yet we have found that on analysis these are 

 all reducible to two very simple and well-defined factors, of 

 responsive contraction and expansion. 



Responsive contraction.— In vegetable cells, as in other 

 protoplasmic bodies, it has been shown that the impact of all 

 external stimulus evokes responsive contraction ; and this 

 we found to be true, not in the so-called sensitive plants 

 alone, but in all plants. Taking the simple case of a radial 

 vegetable organ, such as a stem, style, stamen, or other 

 filamentous structure, we find that it undergoes longitudinal 

 contraction under stimulation. Here, then, we have a phe- 

 nomenon which is analogous to the contraction of muscle, 

 The amount of contraction of these ordinary vegetable 

 organs, further, is sometimes very considerable, as we saw in 

 the case of the coronal filament of Passiflora, where it was 

 as great as 20 per cent, of the original length. Such 

 responsive contraction takes place, moreover, under all forms 

 of stimulation, mechanical, thermal, electrical, photic, and 

 chemical ; and we have found that all the various move- 



