1914] on Plant-Autographs and their Revelations 185 



but too well. The gorged plant is seen to have lost all power of 

 movement. I was, however, able to restore the plant to normal 

 condition by extracting the excess of liquid by application of glycerin 

 (Fig. 10). ^ 



UNIVERSAL Sensitiveness of Plants. 



It may be urged that the various reactions of irritabihty may 

 hold good only in the case of the particular plant Mimosa, and that 

 the majority of plants are quite insensitive. I shall presently show 

 that this view is quite erroneous. In Mimosa diffuse stimulation 

 causes relatively greater contraction of the more excitable lower half 

 of the pulvinus, and this differential action is magnitied by the long 

 petiolar index. Had the upper half of the pulvinus been equally 

 excitable as the lower, then the antagonistic reactions would have 

 balanced each other. In radial organs we do not observe any lateral 

 movement as in Mimosa. This is not owing to insensitiveness, but to 

 equal contractions on all sides balancing each other. The shortening 

 of length of various radial organs like soft stem, tendril, pistil, and 

 stamen, can easily be shown by means of magnifying levers. Again, 

 if we take a hollow tubular organ of some ordinary plant, say the 

 peduncle of daffodil, it is clear that the protected inner side of the 

 tube must be the more excitable. When this is cut in the form of a 

 spiral strip and excited by means of an electric shock, we observe a 

 responsive movement by curling, brought about by greater contrac- 

 tion of the inside of the strip. If again we take a tendril which has 

 curled round a support, the outside is fresh and free from irritation 

 and therefore more excitable. In this case the response is by 

 uncurling, due to greater contraction of the more excifeable outer side 

 of the spiral. 



In the case of woody plants, responsive movement is prevented by 

 the rigid support. Even in such a case I have been able to demon- 

 strate its excitation by means of electric response, first exhibited at 

 this very hall thirteen years ago.* No plant could appear more 

 stolid and irresponsive than the common mdish ; appearances are, 

 however, deceptive, and we find it giving a series of vigorous 

 responses in answer to successive stimuli. The electric response 

 comes to an end with the death of the plant. 



Latent Peeiod of Plant. 



I next take up the very difficult problem of finding out how long 

 it takes for the plant to perceive and respond to a blow. In attempt- 

 ing to make such measurements the results are vitiated by our 

 personal limitations. The conditions of the experiment demand 



* Bose — Friday Evening Discourse. May 10, 1901. 



