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II. Of the Formation of the Vegetable Epidermis, By the Rev. 



Patrick Keith, F.L.S. 



Head March 7, 1815. 



XiiE pellicle that constitutes the vegetable epidermis has gene- 

 rally been regarded as a membrane essentially distinct from the 

 parts which it invests, and as generated with a view to the dis- 

 charge of some peculiar functions in the vegetable ceconomy. 

 Some phytologists, however, have viewed it in a light altogether 

 different, and have regarded it as being merely the effect of acci- 

 dent, and nothing more than a scurf formed upon the exterior 

 and pulpy surface of the parenchyma indurated by the action 

 of the air. This was the opinion of Grew and Malpighi, and, 

 though it does not seem to have ever met with any very general 

 reception, has been revived of late by M. Mirbel, who, pro- 

 fessing to be dissatisfied with the analogy that has generally 

 been thought to exist between the epidermis of the animal and 

 vegetable, contends that the latter is nothing more than the in- 

 durated surface of the parenchyma, from which it differs only in 

 such circumstances as are occasioned by position. If it is more 

 or less transparent; if it is tougher and firmer in its texture than 

 the parenchyma, or any of its parts ; it is only because it is con- 

 stantly exposed to the influence of light and air, and to the con- 

 tact of such bodies as float in the atmosphere ; but it is not to 

 be regarded as constituting a distinct organ or membrane; or as 



exhibiting 



