THE GEOLOGIST. 



but the interior T\'as replaced with sandstone, retaining no structure, 

 but bearing, however, the rude flutings which distinguish the casts of 

 Sigillarice : it ajDpeared to belong to the species Sig'iUaria organum. 

 The sandstone in which it stood consists of several beds ; the lines of 

 stratification distinctly passing through the fossil, and curving more 

 or less downward on all sides towards it. No roots could be observed 

 attached to this tree ; yet from its position at right angles to the 

 strata, and the peculiarity of the stratification, I think it originally 

 grew on the spot. Indeed, there seems to me little doubt that most 

 of the coal-seams, even in northern Northumberland, have been formed 

 of plants and trees which grew, during the Carboniferous Era, in the 

 district now occupied by the coal-beds ; the uuder-clay usually beneath 

 each coal-seam having been the surface-soil on which they grew, it is 

 now found more or less traversed by the Stigmaria Jicoides, — the roots 

 of Sigillarite, — the trunks of which have largely contributed to the 

 formation of the coal. As this fossil tree is frequently to be seen iu 

 Northumberland, it may add to the interest of these notes to give the 

 following description from my Fossil Flora of the Eastern Borders." 



The structure of the Sigillarice differs widely from that of any living 

 plant j it is, however, essentially acrogenous ; and the nearest analogue 

 to those majestic trees of other times is the Lycopod or lowly-creeping 

 club-moss ; yet the radial arrangement of the woody tissue and the 

 presence of medullary rays and a sheath bring them into a distant re- 

 lationship to exogenous vegetation. Brongniart considers them allied 

 both to the Lycopod and to the Cycas ; they form, therefore, a con- 

 necting link between orders which stand far apai-t in existing nature. 

 Composed chiefly of cellular tissue, the Sigillariis were extremely suc- 

 culent ; they grew in swamps and marshes, their long and numerous 

 roots aud rootlets (Stigmaria) forming an entangled mass and per- 

 meating the mud in all directions, in a manner similar to that of the 

 living water-lily in shallow lakes and pools. The roots sometimes ex- 

 hibited a crucial arrangement, uniting into four main portions, sepa- 

 rated from each other by deep channels and forming a dome, from the 

 summit of which the fiuTowed and scarred stems, clothed in the upper 

 parts with a long, narrow, and pendent foliage, rose to the height of 

 nearly 100 feet." 



* Tate's " Fossil Flora of the ]Mountain Limestone Formation," in Dr. John- 

 ston's " Botany of the Eastern Borders," p. 299. 



