64 THE MEDALS OF CREATION. | Cuar. IV. | 
tyledons ; and the entire absence of any rind, the crypto- 
gamia. 
The markings on the stems, occasioned by the scars or 
cicatrices left by the separation of the petioles or leaf-stalks 
(as on the stalk of a cabbage), afford important evidence, 
since they are commonly present, even when the cylin- 
drical trunk is compressed into a flat thin layer of coal ; as 
we shall often have occasion to remark. In this place it © 
need only be stated, that by these scars may be detected © 
the position of the leaves, and the form of the bases of the © 
petioles or leaf-stalks ; their probable direction, whether they — 
were opposite, alternate, verticillate or spirally disposed, 
deciduous or persistent, imbricated or remote. Even when 
no traces of the leaves remain, the origin of the branches, 
and their bifurcation, may perhaps be determinable. 
2. The Leaves.—In a fossil state the texture and surface 
of the leaves are sometimes preserved ; but in general the 
outline of the leaf, its division and arrangement, and its 
mode of venation, can alone be ascertained. The venation, 
that is, the form and distribution of the vascular tissue, or 
vessels, through the leaf, is the most important character for — 
our guidance ; and Dr. Lindley offers the following sugges- 
tions on this point. If the veins be all parallel, not branched, 
or only connected by little transverse bars, and the leaves 
undivided (as in the Lily or Hyacinth), the plant was pro- 
bably endogenous ; but if the leaf be divided or pinnated, it 
may be referable to Cycadez (Lign. 45). 
Leaves having the veins of equal, or nearly equal thick- 
ness, and dichotomous (forked), or very fine, and simply 
divided, belong to the fern tribe ; to this division an immense 
proportion of the foliage found in the carboniferous strata is 
referable ; the genera of fossil ferns have been constructed 
principally from the venation. 
If the veins of a leaf be obviously of unequal thickness, 
and reticulated, or disposed in net-like meshes, as in the 
