OF VEGETABLE TISSUE. 29 



the muscles in the animal body ; for example, 

 when the base of the stamen of the Berberis is 

 pricked with a needle, it is seen to depress itself 

 towards the pistil. If the hairs of the Drosera 

 are irritated, they press themselves close to the 

 leaf ; and one instance, especially, must be fami- 

 liar to most persons, viz. the closing of the leaves 

 of the Mimosa pudica, or sensitive plant, on the 

 slightest touch. It has, however, been conjec- 

 tured that all this class of facts may be referred 

 to vital excitability alone ; and with respect to 

 the third quality, which some persons have attri- 

 buted to plants, sensibility, or more properly 

 sensation, until much more positive proof of it 

 shall be adduced than has yet been offered, 

 it can only be classed with those phenomena 

 which are referrible to excitability. The same 

 argument, from analogy, which leads us to sup- 

 pose that the lower orders of animals are far 

 less sensitive than the higher, is against the idea 

 that plants, wholly unprovided as they are with 

 any apparatus of nerves, can be susceptible of 

 those impressions, whether of pain or pleasure, 

 which in the animal economy we have every 

 reason to refer to a particular portion of the 

 nervous system : nor can we see in the general 

 order of things any sufficient cause to lead us to 



