LEPIDODENDRA. 139 
branches. One specimen, forty feet high, and thirteen feet 
in diameter at the base, divided towards the summit into fif- 
teen or twenty branches, was discovered in the Jarrow coal- 
mine.* The foliage consists of simple, linear leaves, spirally 
arranged around the stem, and appears to have been shed 
from the base of the tree with age. The scars produced by 
the attachment of the petioles were persistent; and the 
twigs and branches are generally found covered with foliage, 
as in Lign. 39. The roots are Stigmariz, like those of the 
Sigillarize, as proved by specimens in the Pictou coal-field, 
discovered by Mr. Brown.t 
The internal organization of the stem of Lepidodendron 
differs from that of Sigillaria, in the absence of the woody 
cylinder and medullary rays which constitute so peculiar 
and important a character in the latter. The Lepidodendra 
have only an eccentric, vascular, medullary zone, the in- 
terval between which and the bark is filled up by cellular 
tissue.t In their structure, external configuration, mode of 
ramification, and disposition of the leaves, they accord so 
closely with the Lycopodiacee, that, notwithstanding the 
disparity in size, M. Brongniart, Dr. Joseph Hooker, and 
other eminent botanists, concur in regarding them as gigantic 
arborescent club-mosses.§ The living species of Lycopo- 
diaceze amount to nearly two hundred, the greater number 
of which, like the arborescent ferns, inhabit the islands of 
intertropical regions. They are diminutive plants, with 
delicate foliage, none exceeding three feet in height ; most 
* Wond. p. 722. This specimen is figured and described in Foss. 
Flor. 
+ Petrifactions, p. 39. 
t See M. Ad. Brongniart, Archives du Muséum d’Hist. Nat. tom. i. 
(for 1839), pl. xxx. 
§ Figures of Lepidodendra in Wond. p. 718. Pict. Atlas, pl. i. 
lil. ix. XXVi. XXVii. XXXili. 
