64 
THE GEOLOGIST. 
but the interior was replaced with sandstone, retaining no structure, 
but bearing, liowever, tlie rude flutings which distinguish the casts of 
Sigillaria; : it appeared to belong to the species Siyillaria 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 sj^ot. 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 under-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 Sigillarise, — the trunks of which have largely contributed to the 
formation of the coal. As this fossil tree is frequently to be seen in 
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 Sigillariae differs widely from that of any living 
plant ; 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. Brouguiart considers them allied 
both to the Lycopod and to the Cycas ; they form, therefore, a con- 
necting link between ordei-s which stand far apart in existing nature. 
Composed chiefly of cellular tissue, the Sigillarioe were extremely suc- 
culent ; they grew in swamps and marshes, their long and numerous 
roots and 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 furrowed 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 Ea-stem Borders," p. 299. 
