Microscopical Essays. 



fiderable diftances from each other. After a lapfe of fifteen 

 years, this new rind did not appear like the natural rind of the 

 cherry-tree. From thefe experiments we learn, that the rind re- 

 generates more readily in fome cafes than in others, and that it 

 preferves and prevents in a degree the bark from becoming dry 

 too foon, and in confequence thereof exfoliating. 



Aided by the microfcope, a number of luminous points may 

 be difcovered in the rind ; * thefe are fo many minute holes for 

 other purpofes of tranfpiration. In the ^ane thefe holes are vifible 

 to the naked eye. A few oval holes may alfo be perceived in it; 

 thefe are, however, no more than a feparation of the parts, oc- 

 cafioned by the extenfion of the vafa interiors 



Dr. Grew fuppofed the rind to be formed of fmall veficles, or 

 bladders, cluttered together, and intermixed with lignous fibres 

 or vefTels, which run through the length of the rind ; thefe are 

 conjoined by other tranfverfe ones, but that as the rind dries, the 

 bladders or blebs Ihrink up and difappear. This account does 

 not differ much from that of Dr. Hill, who fays, that the rind is 

 formed of a feries of longitudinal veffels, and a filmy fubftance 

 between them, which, when viewed in a tranfverfe feclion, form 

 fmall circles, the fides of which are fupported and made up of 

 thefe longitudinal fibres ; that the tranfverfe vefTels are only a de- 

 ception, occafioned by the fpaces between part and part of the 

 film. The mode of obtaining an accurate view of the organiza- 

 tion of this part, by conveying coloured liquors into the feveral 

 veflels thereof, has been already defcribed in page i 62 of thefe 



4 L eflays ; 



* Diihamel Phyfique .des Arbres, vol 1, p. 9. 



