SECT. II. COMPOSITE ORGANS. 213 



experiment had been performed, and the result as- 

 certained, even in the time of Theophrastus.* The 

 pith cannot therefore be regarded as correspond- 

 ing to the spinal marrow of animals, in any thing at 

 all essential. 



Hence it appears that the peculiar function of the 

 pith has not yet been altogether satisfactorily ascer- 

 tained ; and the difficulty of ascertaining it has been 

 thought to be increased from the circumstance of its 

 seeming to be only of a temporary use in the pro- 

 cess of vegetation, by its disappearing altogether in 

 the aged trunk. But although it is thus only tem- 

 porary as relative to the body of the trunk, yet it 

 is by no means temporary as relative to the process 

 of vegetation ; the central part of the aged trunk 

 being now no longer in a vegetating state, and the 

 pith being always present in one shape or other in the 

 annual plant, or in the new additions that are an- 

 nually made to perennials. The pith then is essential 

 to vegetation in all its stages : and from the analogy 

 of its structure to that of the pulp or parenchyma 

 which is known to be an organ of elaboration, as in 

 the leaf, the function of the pith is most probably 

 that of giving some peculiar elaboration to the sap, 

 according to the hypothesis of Malpighi ; which 

 seems to me to be the best founded of all the fore- 

 going, with the exception of that part of it by 



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 tyvrav &ITKM. TO. E. 



