POSITIVE AND NEGATIVE TURGIDITY-VARIATIONS 6l 



the leaf. We shall now see whether a similar difference 

 exists between the electrical expressions of the positive and 

 negative turgidity-variations. 



In carrying out this experiment, I took a specimen of 

 Biophytum and applied stimulus at a distance from the par- 

 ticular leaflet whose responses were to be observed, arranging, 

 at the same time, for a simultaneous record of the mechanical 

 and electrical responses. It will be seen from fig. 46 that the 

 preliminary erectile twitch, due to the positive turgidity- 

 variation, has, as its concomitant, galvanometric positivity. 

 And this is followed in both records by its opposite : namely, 

 the contractile fall and the galvanometric negativity of true 

 excitation. 



It will thus be seen that the increase of internal energy, with 

 its positive turgidity-variation, has, as its electrical expression, 

 galvanometric positivity. Besides this, the mere physical 

 movement of water in 

 the tissue gives rise to 

 a certain electrical varia- 

 tion of positivity, and 

 this can still be detected, 

 even after the tissue is 

 killed. The question of 

 how to discriminate what 

 proportion of the electro- 

 positivity was due to this 

 mere water - movement, 

 and what to the increase 

 of turgidity, associated 

 with the increase of in- 

 ternal energy, I at first 

 found it very difficult to 

 decide. But I ultimately 

 succeeded in doing this 

 by bringing a plant to 

 a condition just short of 



FIG. 46. The Abnormal Positive preceding 

 the Normal Negative in Mechanical and 

 Electrical Responses in Biophytum 



x represents the moment of application of 

 stimulus. The upper is the mechanical 

 and the lower the electrical record. 

 The records downward indicate erection 

 of the leaf or galvanometric positivity. 



death, and thus abolishing its 



true excitatory reaction. In this condition, the responsive 



