II. Of the Formation of the Vegetable Epidermis.By the Rev. Patrick Keith, F.L.S.
Read March 7, 1815.
The pellicle that constitutes the vegetable epidermis has generally been regarded as a membrane essentially distinct from the parts which it invests, and as generated with a view to the discharge of some peculiar functions in the vegetable œconomy. Some phytologists, however, have viewed it in a light altogether different, and have regarded it as being merely the effect of accident, 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, professing 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 indurated 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 constantly exposed to the influence of light and air, and to the contact of such bodies as float in the atmosphere; but it is not to be regarded as constituting a distinct organ or membrane; or as
