360 PHYTOLOGY. 



Of Relaxation in Vegetables. — There is an action, in plants which 

 appears to be the contrary of expansion; it may be considered as a 

 relaxation, or an action of those parts antagonizing the others which 

 acted through the day, or at other periods, and takes place at the time 

 these other parts cease to act. 



This action has hitherto been considered as analogous to sleep in 

 animals, whereas sleep is a total loss of the sensitive principle and all 

 the actions dependent on volition for the time, and therefore can only 

 take place in animals endowed with sensation*. It is rather a defect 

 in the animal than an action or the exertion of a principle. 



This action of relaxation is seen in the sensitive plant when the 

 folioles close upwards and are kept bent by the power of action in the 

 flexors, till light and some other of its attendants affect it, when the 

 extensors begin to act, and this action of the flexors ceases. The foot- 

 stalk dropping down favours the idea of simple relaxation ; but this only 

 arises from the position of the plant, for if turned upside down it still 

 bends against its own gravity 1 . 



The one action is produced by the stimulus of light, the other by that 

 of darkness ; for if the sensitive plant is kept in a dark room it will 

 keep bent, and perhaps as long as it lives ; and if one part of the plant 

 is kept in the dark and the other in the light, that in the dark will be 

 bent, and continue so, while that in the light will expand itself. 



Light and darkness become stimuli to the same plant, and have much 

 more influence over vegetables than coidd at first be imagined. Many 

 plants only grow through the day, others only grow after it is dark. 



Sympathy in Vegetables. 



Sympathy is the action of one part in consequence of an application 

 being made to another part, or action in another part. 



This power of action is extended to few plants, and even in these ap- 

 pears to have little variation. It is evident in the sensitive plant ; for 

 if one of the little leaves be wounded at its termination it will collapse 

 immediately, as also its fellow on the other side. This action runs 

 through the whole of the rachis of the compound leaves, the leaves bend- 

 ing regularly in pairs. 



If it is a middle foliole that is wounded the same thing takes place ; 

 they all collapse towards the footstalk, but seldom towards the extreme 

 * The polypus does not sleep. 



1 [The powers which produce the depression and elevation of the leaf-stalk ope- 

 rate in a manner precisely the reverse of the flexor and extensor muscles in animals, 

 pushing the moving part from, instead of pulling it towards, the fixed point. The 

 distension and collapse of cells through movement of the sap, appear to be the chief 

 physical changes accompanying these movements.] 



