"
[Illustration: Fig. 110.--_Lepidodendron Sternbergii_, Carboniferous,
Europe. The central figure represents a portion of the trunk with
its branches, much reduced in size. The right-hand figure is
a portion of a branch with the leaves partially attached to it;
and the left-hand figure represents the end of a branch bearing
a cone of fructification.]
The _Lepidodendroids_, represented mainly by the genus
_Lepidodendron_ itself (fig. 110), were large tree-like plants,
which attain their maximum in the Carboniferous period, but which
appear to commence in the Upper Silurian, are well represented in
the Devonian, and survive in a diminished form into the Permian.
The trunks of the larger species of _Lepidodendron_ at times
reach a length of fifty feet and upwards, giving off branches in
a regular bifurcating manner. The bark is marked with numerous
rhombic or oval scars, arranged in quincunx order, and indicating
the points where the long, needle-shaped leaves were formerly
attached. The fruit consisted of cones or spikes, carried at the
ends of the branches, and consisting of a central axis surrounded
by overlapping scales, each of which supports a "spore-case"
or seed-vessel. These cones have commonly been described under
the name of _Lepidostrobi_. In the structure of the trunk there
is nothing comparable to what is found in existing trees, there
being a thick bark surrounding a zone principally composed of
"scalariform" vessels, this in turn enclosing a large central
pith.
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