Br. Bell on the Vhyfiokgy of Plants, 41 1 



this fubjeft is as difficult, as it is important, 

 and, as yet, it is not precifely underftood, even 

 by the moft curious obfervers. I am led to engage 

 jn it more by the pleafing nature of the ftudy, 

 than the hope of furpaffing thofe who have 

 gone before me; and I purpofe, in the following 

 Eflay, to confine myfclf to a few remarks on the 

 ftrudure, life, and funflions, of vegetables. 



It is proper to premlfe, that if the anatomy 

 of plants be not demonftrated throughout, with 

 all the clearnefs that could be wiftied, this arifes 

 from their containing parts of fuch a degree of 

 minutenefs, that they elude the human fight. 

 The nature of thefe mufi: therefore frequently be 

 inferred from analogy only, which is often falla- 

 cious. But many things have been afcertained 

 on this fubje^l, and with thefe I Ihall begin. 



On making a tranfverfe fcclion of a tree, it 

 appears to confift of three diftincl parts — the 

 bark — the wood — and the medulla, or pith. 



I. The bark confifts of two parts — the cuticle, 

 and the true baik. The cuticle of plants affords 

 an external covering to all their parts. It con- 

 fifts of numerous layers, eafily feparable from 

 f ach other, and of which the fibres are circular.* 



The 



• Dr. Hill, by the ufe of magnifying glaiTes, firft dif- 

 Covered the cuticle to be an organized body, containing 

 longitudinal veflels, and veficles, Sec He however thought, 

 the cuticle was formed merely by the hardening of the 

 fuperficies of the true bark, when expofed to the external 



air. 



