IRRITABILITY OF PLANTS 151 



permanently stilled" with the cessation of life (Fig. 16). But the 

 rate of the death-march has been successfully retarded by means 

 of nourishing solutions ; the throbbing life of the cut leaflet 

 has thus been prolonged from one to seven days. 



In cutting off the leaf of Mimosa the sensibility of the plant 

 is paralysed for several hours. The paralysing effect of the 

 wound was determined by means of testing shocks, the response 

 being at the same time taken down by the automatic recorder. 

 The parent plant gradually recovered, and showed signs of 

 returning sensitiveness. The detached leaf also recovered its 

 sensibility in a few hours, and exhibited its normal responses. 

 But this vehemence lasted only for a day, after which a curious 

 change crept in ; the vigour of its responses began rapidly to 



FIG. 1 6. Abolition of pulsation at the death of the 

 plant. 



decline. The leaf, hitherto erect, fell over death had at last 

 asserted its mastery. 



As regards the comparison of the general phenomenon 

 of Irritability in plants and animals, Bose says : 



We find that the plant is not a mere mass of vegetative 

 growth, but that its every fibre is instinct with sensibility. We 

 find it answering to outside stimuli, the responsive twitches 

 increasing with the strength of the blow that impinges on it. 

 We are able to record the throbs of its pulsating life, and 

 find these wax and wane according to the life conditions of the 

 plant, and cease with the death of the organism. We find 

 the different parts of the plant are connected together by 

 conducting threads, so that the tremor of excitation initiated 

 at one place courses through the whole, this nervous impulse, 

 as in man, being accelerated or arrested under the several 

 actions of drugs and poisons. In these and in many other 



