252 Account of the Fossil Trees found at St. Helenas. 



having several veins originating from the rachis, circumstances 

 very different from those which prevail in true ferns, more 

 particularly in the Pecopt^ris, and which appear to connect it 

 with Odontopteris, a fornv very nearly allied to Otopteris, a 

 fossil of decided cycadeous type, occurring along with other 

 cycadeous forms in-' the Yorkshire oolite*. 



The roots of Sigillaria are more abundant than any other 

 remains which occur in the coal formation, and the smaller 

 fibrils abound to such a degree in coal floors, that it is scarcely 

 possible to obtain a hand specimen of one of them without 

 meeting with some trace of the rootlets of Stigmaria; and in 

 most of the floors these roots are met with unassociated with 

 any other description of plant. 



This great abundance of the roots in floors, and the very 

 frequent occurrence of stems of Sigillaria in various states in 

 the coal deposits, would almost justify the supposition that this 

 plant had, by its destruction, formed the chief portion of our 

 coal seams, an opinion which is further confirmed when we 

 remember that such portions of coal as show traces of internal 

 organization have decidedly a gymnospermous character. 



The upright position of many of these stems also seems to 

 lead to the conclusion, that these trees have not been trans- 

 ported by the agency of water, but rather that they have pe- 

 rished on the spot where they originally grew, most probably 

 by some such cause as a subsidence of the locality, to which 

 circumstance it is probable that we owe the formation of all 

 our coal deposits with floors containing Stigmaria. 



The external character, the internal structure, and all the 

 circumstances under which Sigillaria occur, render the sup- 

 position that this plant was of a partially aquatic nature, and 

 required a watery habitat, exceedingly probable. Its roots 

 most commonly occur in a deposit which was originally soft 

 mud, through which the rootlets struck for a considerable di- 

 stance in all directions : the quincunx order of the arrange- 

 ment of the scars which cover the main roots also justifies the 

 conclusion as to the nature of the habitat in which it grew and 

 flourished during the e()och when |)lant^ were grailually puri- 

 fying the atmos[)here and rendering it fit for the respiration 

 of vertebrated animals. 



* The authors are unable to conceive on what grounds Lindley and 

 Hutton have referred this specimen to Pecopteris, having only the adhe- 

 rence of its base to the rachis to identify it with this genus, and wanting 

 entirely the distinct midrib from whence the veins originate. 



