426 
ELEMENTS OF GEOLOGY. 
Sigillaria Icevigata, Brong. 
some degree, in the form of the cica¬ 
trices left by the base of the leaf¬ 
stalks which have fallen off (see 
Fig. 464). But some of them are 
ascertained to have had long linear 
leaves, quite unlike those of ferns. 
They grew to a great height, from 
30 to 60, or even 70 feet, with regu¬ 
lar cylindrical stems, and without 
branches, although some species were 
dichotomous towards the top. Their 
fluted trunks, from one to five feet in 
diameter, appear to have decayed 
more rapidly in the interior than ex¬ 
ternally, so that they became hollow 
when standing; and when thrown 
prostrate, they were squeezed down 
and flattened. Hence, we find the 
bark of the two opposite sides (now converted into bright 
shining coal) constitute two horizontal layers, one upon the 
other, half an inch, or an inch, in their united thickness. 
These same trunks, when they are placed obliquely or ver¬ 
tically to the planes of stratification, retain their original 
rounded form, and are uncompressed, the cylinder of bark 
having been filled with sand, which now affords a cast of the 
interior. 
Dr. Hooker inclined to the belief that the SigillaricB may 
have been cryptogamous, though more highly developed 
than any flowerless plants now living. Dr. Dawson having 
found in some species what he regards as medullary rays, 
thinks with Brongniart that they have some relation to gym- 
nogens, while Mr. Carruthers leans to the opinion that they 
belong to the Lycopodiacese. 
Stigmaria ,—^This fossil, the importance of which has al¬ 
ready been pointed out, p. 398, was originally conjectured to 
be an aquatic plant. It is now ascertained to be the root of 
Sigillaria. The connection of the roots with the stem, pre¬ 
viously suspected, on botanical grounds, by Brongniart, was 
first proved, by actual contact, in the Lancashire coal-field, 
by Mr. Binney. The fact has lately been shown, even more 
distinctly, by Mr. Richard Brown, in his description of the 
Stigmarice occurring in the under-clays of the coal-seams of 
the Island of Cape Breton, in ISTova Scotia. In a specimen 
of one of these, represented in the annexed figure (Fig. 465), 
the spread of the roots was sixteen feet, and some of them 
sent out rootlets, in all directions, into the surrounding clay. 
