IRRITABILITY. ZO 



ly demonstrated by an experiment of Von Uslar. He 

 destroyed the life of a plant by electricity, without af- 

 fecting its organization, after which an incision of its 

 branches was not followed by an effusion of fluids, 

 though previous to the experiment it bled abundantly. 

 It may also be exhibited by two transverse sections of a 

 twig, from each extremity of which a fluid may be ob- 

 served to escape. 



Sensibility differs from the preceding property of 

 vegetable life, by its supposed association with pleas- 

 ure and pain. A little attention to this subject will 

 convince us, that plants distinguish heat from cold, 

 darkness from light, and the other sensible properties 

 of the atmosphere which promote, from those which 

 retard vegetation. Thus when plants are placed by 

 our windows, we see them present the upper surface 

 of their leaves to the light ; and when their position is 

 reversed, a new arrangement of the leaves takes place, 

 by which the same surface is again exposed to the rays 

 of the sun. Some flowers which shine with distinguish- 

 ing lustre in the morning, shrink from the dazzling 

 brightness of a noon day sun ; some court his meridian 

 glory, while others at the approach of darkness, expand 

 their tender blossoms, loading with perfume the breez- 

 es of evening. Thus too, we find the leaves of some 

 plants closing around their tender blossoms, to protect 

 them from the injurious effects of cold and moisture , 

 and others exquisitely sensible to the touch of extrane- 

 ous bodies. The flowers of the Barberry, a shrub 

 which grows abundantly in every section of the United 

 States, evince a susceptibility of impression from exter- 

 nal objects, at once curious and surprising. The 

 leaves of the Sensitive, so often the innocent source of 

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