36 



Remarks on the Decay of 



the outside of the epidermis, nor were they at all visible on 

 the remains of the soft part which had been in contact with it. 

 Fig, 19. is a portion of the stem, or lignum^ from which, 

 when perfectly dry, its bark has been removed by peeling. It 

 formed a hard and tough cylinder, of moderate thickness, 

 the longitudinal striae being only interrupted by the slightly 

 elevated spots which held the spinous nerves as they emerged 

 from the wood, and then passed through the bark, where they 

 formed the external rugae. That part of the bark which 

 immediately covered the wood retained the same impressions 

 on its surface, but that in contact with the epidermis had 

 large tubercles corresponding with the outside of the plant; 

 but in no case did this portion of the bark exhibit a pattern 

 dissimilar from it. 



In fossil plants it has been remarked that the same species 

 may appear under three different states; such as are produced 

 by the epidermal, cortical, and ligneous configurations : the 

 first and the last differing much from each other ; and, as 

 Mr. Parkinson states, " it is only close observation that deter- 

 mines that it originates from the same plant." 



Assuming that fossil succulent plants have undergone 

 changes similar to those here represented, either before they 

 were lodged in their matrix, or when so embedded, it will be 

 easily perceived that one species may appear under several 

 aspects difficult to determine. It is not improbable that, 

 during the progress of maceration in the matrix, a variety of 

 circumstances may have occurred to favour these changes and 

 variations. 



In contrasting these observations with what is visible in the 

 submarine peat found in these islands, many indications point 

 out a similar decomposition to be going on; and although 

 these trees and vegetables have been buried many centuries, 

 and are of a different description from those under notice, yet 

 they exhibit changes nearly as difficult to recognise. 



