Trunk and branch fossils (Lepidodendron)Most reconstructions of Lepidodendron
are misleading: they show only the final mature stage with a crown of branches, but during its short life (estimated at 10 to 15 years) it grew as an unbranched "pole" with spirals of leaves around its trunk. Unlike modern trees, no secondary phloem (cells which transport food products around the plant) was produced at all in Lepidodendron.
Much of the interior was of soft cellular pith which collapsed after death, and, unlike modern trees, these plants were strengthened by the growth of a strong outer cortex. It was the cortex which provided the support for the tall trunks of these plants, and the interior is often fossilised as a sediment filled space. Branches are common fossils, often found flattened, or partially filled with sediment, and, because they were partly compressed during burial, these are usually oval shaped in cross section.
The scaly surface pattern is made up of the leaf scars left behind on the cortex during leaf-fall. It is this leaf pattern that gives the fossil its common name of "Scale Tree". The leaves grew directly from the trunk (not with a stalk) and they always form a spiral around the stem, indicating that the leaves formed a helix around the main axis.
Leaf fossils (Lepidophylloides)
The leaves on Lepidodendron
grew to different sizes depending on which part of the plant they were found. The largest leaves could reach up to a metre in length whilst only being a few centimetres in width. The leaves had a single central vascular bundle (for water transfer) and two grooves on the lower surface with stomata for gas exchange. The distinctive leaf base pattern on the trunk and branches was covered by cuticle, had stomata and was involved in photosynthesis along with the leaves.