134 THE MEDALS OF CREATION. Cuap. VI. 
When Stigmariz are observed in the under-clay, to which 
stratum they are principally confined, long, tapering, sub- 
cylindrical fibres, often several feet in length, are seen 
affixed to the tubercles with which the surface is covered ; 
their form and mode of attachment are shown in Lign, 36. 
Instances occur in which several Stigmariz spring from a 
common centre, of a dome-like form, whence they radiate 
in every direction (Ld. pl. lvi. fig. 8), and the main branches 
divide and subdivide till they are lost in the surrounding 
rock, 
The nature of these fossil vegetables was long a perplexing 
question, for no specimens had been found in connexion with 
any of the stems, branches, or foliage, that abound in the 
coal deposits. At length, the discovery of a dome-shaped 
mass, to which were attached numerous Stigmarie, seemed 
to afford a clue to the solution of this botanical problem; 
and it was concluded by the eminent authors of the “ Fossil 
Flora of Great Britain,” that the original belonged to a tribe 
of plants which inhabited swamps, or still and shallow lakes, 
and were characterized by a low truncated stem, having 
long horizontal branches beset with cylindrical, and, pro- 
bably, succulent leaves, that either trailed on the surface of 
the swamp, or floated in the water. 
But within the last few years, the occurrence in various 
carboniferous deposits of erect stems of Sigillarize, has shown 
that the Stigmarize are nothing more than the roots of these 
and other congenerous trees ; an opinion maintained by the 
Rey. H. Steinhaur more than thirty years ago, and subse- 
quently affirmed by M. Adolphe Brongniart, who found, on 
examining microscopically the internal structure of a silici- 
fied specimen in which the vascular tissue was preserved, 
that it bore as close an analogy to that of the Sigillariz, as 
exists between the roots and trunks of certain dicotyledonous 
trees. 
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