66^ Microscopical Essays. 



•dimiriifhing gradually in fize as they are more interior, and form- 

 ing as it were fo many conical cells. 



' We may, I think, conclude from what has been faid, that the 

 bark is compofed of feveral thin membranes, which extend over 

 the whole exterior furface of the tree. The moft exterior mem- 

 brane is the rind $ under this is what Duhamel calls the cellular 

 coat; next to this the cortical ftratum, or true bark of the tree, 

 which is formed of lymphatic veftels ranged more or lefo in a 

 reticular form, and of the vafa propria interiora. The mefhes 

 ; are fo conftituted as to form large cavities next the rind, and 

 fmall ones near the wood. Thefe cavities are filled with a 

 parenchymous fubftance or the cellular tiffue, which being con- 

 tinued from the wood to the rind, joins and unites the cortical 

 ftratum, and afterwards fpreading on the outfide thereof, forms 

 -what has been termed the cellular coat. 



Of the Cellular Tissue. 



We now proceed to give fome account of the fubftance which 

 fills up the vacant fpaces that are left between the longitudinal 

 fibres. It is called by Grew the parenchyma or pulp, by Mal- 

 phigi, the veficular tiflue or web j both of them confider it as 

 formed of fmall bladders or reticules, that are in contact with 

 each other, lying in an horizontal pofition, or at right angles to 

 the longitudinal fibres : they do not fuppofethem to be all of the 

 fame fize, or even of the fame figure : Grew compares it to jthe 

 froth of beer or eggs. The flelh of fruits confifts for the moft 

 ( part of this fubftance, very much filled with juice, though -with 

 .considerable difference in it's organization, Be this as it may, 



ttbe 



