so THE PHILOSOPHY 



This fliort account of the general ftrucHiure of animals was 

 a necefTary preparation for perceiving more clearly their con* 

 ne(Slion with the vegetable kingdom. 



The ftructure of plants, like that of animals, confifts of a 

 feries of veiTels difpofed in a regular order. Thefe veflels 

 are deftined to perform the different functions neceflary to 

 the nourllhment, growth, and diflemination of the plant. In 

 trees, and moft of the larger vegetables, three diftin<Sl: parts 

 are to be obferved ; the bark, the wood, and the pith. The 

 bark likewife confifts of three parts ; the il-win, the body, and 

 the I'lhery or inner circle j which laft, about the end of au- 

 tumn, aflumes the fame texture and firmnefs with the wood. 

 The lubftance of the bark is compofed of a number of lon- 

 gitudinal fap and air vefTels, which have the appearance of 

 fine threads, running from the root to the trunk and branch- 

 es. Belide thefe veflfels, the bark is furnifhed with a paren- 

 chymatous or pulpy fubftance, in which there are a vafl va» 

 riety of foUkull^ or fmall bladders. The bark is connected to 

 the wood by tranfverfe infertions of the parenchyma. 



The wood confifls of two diftin£t fubftances •, the one is 

 denfe, and compa(SI:, and conftitutes what is termed the lig- 

 neous body ; the other is porous, moift, and pulpy, and is 

 therefore called t\\Q parenchymatous part of the wood. A 

 portion of wood is placed alternately between a fimilar por- 

 tion of parenchyma. Thefe alternate portions proceed from 

 the edges of the pith, as radii from the center of a circle, 

 widening proportionally as they approach the circumference. 

 Both of them, however, like the bark, are furnifhed with 

 numberlefs fap and air vefTels. 



The pith or heart is bounded on all fides by the wood, 

 and is compofed of the fame materials : It Is nothing but a 

 Taft congeries of air and fap vefTels, interwoven with the 

 parenchyma and bladders, not unlike the tifTue of gauze or 

 lace. This texture is common to every part of the trunk. 



