LECT. II. j VITAL FUNCTIONS OF PLANTS. 51 



found in every animal; for many of the lower 

 classes of animated bodies want one or more of 

 them. As is the case in animals, the organs with 

 which plants are furnished are always of the same 

 structure in every individual of the same species, 

 when in a natural and healthy state : and these 

 organs are also susceptible of the same impres- 

 sions from external agents, the circumstances being 

 in every respect equal, in every individual of the 

 same species. Thus any number of seeds of the 

 same kind of Lily will produce Lilies all resem- 

 bling each other in form and structure ; the same 

 number of parts will be evolved, and the unfolding 

 of them take place in the same manner. The dif- 

 ferences of soil, of situation, and of culture may 

 occasion varieties in colour and other unimportant 

 particulars, but the specific characters remain in- 

 variable. These facts are sufficient to prove that 

 plants are endowed with life, or possess the same 

 principle by which the existence of the organic 

 structure, the growth, and the propagation of the 

 species in animals are supported : but let us exa- 

 mine a little more closely those functions of vege- 

 tables which prove their vitality. Although vi- 

 tality cannot properly be defined, yet we know it, 

 when it is present in any object, by its effects, 

 which are never displayed by unorganized matter ; 

 and therefore we are accustomed to define it by 

 saying, it is " that property of matter connected 



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