Chap, i.] *?be Stem or Trunk. 3 



root, the leaf, the flower, the fruit, and the feed. In 

 rnany vegetables the root appears nearly fimilar, in all 

 its conftituent parts and principles, totheftem or trunk, 

 and indeed the one feems a continuation of the other; 

 which muft be my apology for reverfing in fome de- 

 gree the order of nature, and treating firft of .that partj 

 which though it feems to proceed or fpnng immedi- 

 ately from the other-, is yet the moft perfect in its or- 

 ganization, and is in general of the greatelt life- and 

 importance to man. 



I. The item or trunk, which includes alfo the 

 branches, I might fay all the more folid end fubftan- 

 tial parts of a tree or plant, confifts of three parts, the 

 bark, the wood, and the pith. 



lit. The bark is protected en the outfide, by a cuti- 

 cle, epidermis,, or fcarf-fkin, which confifts fometimes 

 of numerous layers, and differs Jn thicknefs in differ- 

 ent plants. This fkin or cuticle is an organized body^ 

 compofed of very minute bladders, often interfperfed 

 with longitudinal woody fibres, as in the nettle, thiftlei 

 and' the generality of herbs. It contains alfo longitu- 

 dinal veiiels, and is vifibly porous in fome plants, and 

 particularly the cane. 



On removing the cuticle, the true bark appears, and 

 may be confidered as a congeries of < pulp or cellular 

 iubftancej in which are placed a number of veffels, as 

 well as longitudinal fibres. The veffels of the bark 

 are differently ficuated, and deftined for various ufes, 

 in different plants. , In the bark of the pine, for in- 

 ftance, the inmoTt are lymph-ducts, exceedingly minute; 

 thofe neareft the iurface are gum or refiniferous veilels, 

 for the fecretion of the turpentine, and thefe are fo large 

 as to be vifible to the naked eye. 



2d. The wood lies between the bark and the pith. 



Its fubltance is denfer than that of the bark, and its 



B 2 flruclur? 



