350 SPONTANEOUS MOVEMENTS IN PLANTS. 



ments, which Ave are unable to distin2;uish in character from those of 

 the lowest animals. It is at their lowest confines, accordingly, that 

 the vegetable and the animal kingdoms approach or meet, and even 

 seem to blend their characters. 



681. 'Wlien we consider that the excitability of sensitive plants 

 is often transmitted, as if by a sort of sympathy, from one part to 

 another ; tliat it is soon exhausted by repeated excitation (as is 

 certainly the case in Diona^a, the Sensitive-Plant, «fcc.), to be re- 

 newed only after a period of repose ; that all plants require a 

 season of repose ; that they consume their products and evolve heat 

 under special circumstances with tlie same results as in the animal 

 kingdom (Chap. VII.) ; that, as if by a kind of instinct, the various 

 organs of the vegetable assume the positions or the directions most 

 favorable to the proper exercise of their functions and the supply of 

 their Avants, to this end surmounting interA'ening obstacles ; when 

 we consider in this connection the still more striking cases of spon- 

 taneous motion that the lower Algse exhibit ; and that all these 

 motions are ai'rested by narcotics, or other poisons, — the narcotic 

 and acrid poisons even producing effects upon vegetables respectively 

 analogous to their different effects upon the animal economy ; we 

 cannot avoid attributing to plants a vitality and a power of " making 

 movements tending to a determinate end," not different in nature, 

 perhaps, from those of the lowest animals. Probably life is essen- 

 tially the same in the two kingdoms ; and to vegetable life faculties 

 are superadded in the lov/er animals, some of which are here and 

 there not indistinctly foreshadowed in plants. 



682. Tlie essential differences between plants and animals Avere 

 enumerated at the commencement of this Avork (16), and have been 

 illustrated in its progress. Distinct as are the general structure 

 and the offices of the tAvo great kinds of organized beings, it is still 

 doubtful Avhether the discrimination is absolute, or whether the 

 functions of the A'egetable and the animal may not, in some micro- 

 scopic organisms, be imposed upon the same individual. 



