M I C R< O S COP I C A'L "E S S A -Y«S. 



Juice Vess.els.. 



f t, The exterior veffels, placed between the rind and the .bark. 

 | 2. The .interior, in the fubftance of the bark. 

 ^1 3. The intimate, in the fubftance of the blea. 

 ^4. The fap veftels, in the fubftance of the wood, 

 5. The coronal, in the corona. 



More accurate inftruments, or a more minute inveftigation o£ 

 the parts, may probably difcover new veftels, in a fyftem which 

 .appears to.be entirely vafcular, and bring us more thoroughly 

 acquainted with the nature of vegetation. 



Of the Rind, 



The exterior covering of all trees is a thin, dry, parched fub- 

 ftance, which has been compared by many writers to the (kin of 

 animals, and called by names analogous thereto ; thus it is called 

 the epidermis by Duhamel, the fkin by Grew, the rind by Hill. 



When a tree is full of fap, this membrane may be eafily de- 

 tached from the part it covers it may be feparated from green 

 branches which are not in fap, by boiling them in water 5 large 

 pieces of it may alfo be obtained from rotten branches ; the rind 

 of the leaves of many trees is detached with fingular dexterity 

 from the other parts, by fome of the mining caterpillars ; artificial 

 methods for effecting this purpofe have been defcribed in page 

 159 of this work. Though the rind may at firft fight be thought 

 to be of little ufe, it will be found to be a principal organ in the 



procefs 



