| Here is a cross section through a branch of a large lepidodendrid tree.
It is around an inch in diameter. In the very center is a pith, surrounded
by primary xylem and a small fringe of seccondary xylem. Then there is
black gunk and an open white area. Phloem and innermost cortical tissues
are typically not well preserved, and this black gunk and white areas probably
represent their positions in the branch. Those circular things in the white
area are stigmarian rootlets that grew through the stem after it was deposited
and part of the "compost" on the forest floor. To the outside you
can see a couple more layers of cortical tissue interrupted by white areas
which are the air channels accompanying leaf traces. The outermost part
of the stem is gone. |
