FOSSIL PLANTS. 
435 
tween them flattened furrows, or strips of true bark with its cicatrices. The 
irregularity of these ridges, which vary in size as well as in their respective 
distances, being sometimes close to each other, sometimes a few inches apart, 
contradict the supposition that they are a kind of organism resulting from the 
normal growth of the trees. They are mere excrescences, similar to those 
which are seen on old trees; for in some places, by the expansion of their bor¬ 
ders they cover part of the scars, in some others they push them aside, as from 
the enlarging border of a split. When supercorticated, the surface of the spe¬ 
cies of this genus between the top of the ribs, is filled by a coat of carbona¬ 
ceous matter, half a line to one line or more in thickness, in such a way that 
the surface of the coat of coal is on a plane with the ridges, and that conse¬ 
quently, the coal is thicker in proportion to the depth of the grooves, as seen, 
pi. xxiiij fig. 1. 
The surface of this coaly matter is smooth, striate lengthwise by narrow par¬ 
allel lines, and the position of the cicatrices of the bark and of the leaf scars 
is merely indicated by a slight depression, with a point in the middle. The 
peculiar nature, or rather the mode of formation of this supercortical coat of 
coal, which covers the surface of the plants now examined, as also of most of 
the species of trees found in the shales and in the sandstone of the Coal 
Measures, is not explained. It is evident from what is seen on our specimens, 
that it does not represent a true cortex, but that it is rather produced by some 
exudation of matter (ulmic acid ?) forced, by compression, during the process 
of maceration and carbonization of the plants. This supposition, however, does 
not account for the peculiar marks left and defined upon the surface of this 
matter, and different in each species, 
^ y /y Ulodendron majus, LI. and Hutt. 
Foss, flora., i, p. 22, t. s. 
Sigillarici Menardi, Lesqx . 
Ill. Geol. Rep , vol. ii, p. 450, PI. 43. 
Large and numerous specimens of this species, obtained from the shales at 
Morris, have afforded opportunity of studying it under various appearances, 
and of recognizing its identity with the species described and figured by Lind- 
ley and by Sternberg. Though the cicatrices are most of the time obliterated, 
and their outline modified, some specimens present them in their primitive 
forms, with the essential characters, the three-pointed leaf scar of the genus 
Lep idodendron. 
They arc rhomboidal in outline, pointed or truncate at the top, rounded at 
the base, enlarged on the obtusely pointed sides, marked in the middle by a 
