CHAP. I. VITAL PROPERTIES AND STIMULANTS. 1 6'3 



by such treatment. The revival of plants among the 

 cryptogamic tribes, after a very long suspension of the 

 vital functions, is well authenticated. 



(148.) Irritability. Besides the excitability of ve- 

 getable Hfe, there are certain striking phenomena ex- 

 hibited by some plants, which seem to indicate the 

 presence of a property analogous to that of animal 

 " irritability." A closer examination, however, of the 

 circumstances under which this " vegetable irritability " 

 manifests itself, rather inclines us to believe with De Can- 

 dolle, until sufficient proof be brought to show the con- 

 trary, that these are only extreme cases of the operation 

 of the property of excitability. The sudden inclination 

 of the stamens in the berberry towards the pistil, when 

 the filaments are touched near the base on the inside, 

 the well-known phenomena exhibited by the sensitive- 

 plant, and several other singular movements of particular 

 organs in some other plants, are the phenomena which 

 have led to the conclusion, that some few vegetables are 

 endowed with an irritability analogous to that which 

 exists in all animals. But on the other hand it has 

 been observed, that in animals this property is confined 

 to the muscular fibre, whilst in vegetables there does 

 not appear to be any particular tissue to which it is 

 peculiarly restricted. In animals, again, the effects of 

 irritability are apparent during the whole course of their 

 life, and are not destroyed by repetition of the experi- 

 ments by which they are elicited ; whereas this property 

 can be traced only under peculiar conditions of vege- 

 table existence, and then only in certain organs of a 

 very few species. Several of these instances, also, are 

 only special modifications of certain actions, which are 

 constantly produced by the operation of more general 

 causes. For instance, the folding of the leaflets of the 

 sensitive-plant, which takes place when we touch them, 

 is the very same sort of effect which we daily witness 

 in a vast number of other plants, where it is elicited 

 by the agency of light, only in a more gradual and 

 M 2 



