Editing Lepidodendron (section)

=== Stem ===
[[File:PSM V18 D629 Lepidodendron modulatum and diplodigioides.jpg|thumb|upright|Leaf scars shown on a ''Lepidodendron''. The "diamond shape" or scale impressions are common indicators of the leaf scars from ''Lepidodendron'' lycophytes.]]
The stem of the lycopsids had a [[Unifacial cambium|unifacial]] [[Vascular cambium|vascular]] cambium, contrasting with the [[Bifacial cambium|bifacial vascular]] cambium of modern trees. Though the bifacial cambium of modern trees produces both secondary [[phloem]] and [[xylem]], the unifacial cambium of ''Lepidodendron'' lycopsid produced only secondary xylem. As the lycopods aged, the wood produced by the unifacial cambium decreased towards the top of the plant such that terminal twigs resembled young ''Lepidodendron'' stems. Compared to modern trees, the stems and branches of the lycopsids contained little wood with the majority of mature stems consisting of a massive [[Cortex (botany)|cortical]] [[meristem]]. The nearly-uniform growth of this cortical tissue indicates no difference in growth during changing seasons, and the absence of dormant [[bud]]s further indicates the lack of [[seasonality]] in ''Lepidodendron'' species.<ref name="Geography" /> The outermost cortex of oldest stems developed into the bark-like [[lycopodiopsid]] [[periderm]].<ref name="Evo">{{cite book |author=Karl J. Niklas |title=The Evolutionary Biology of Plants |publisher=University of Chicago Press |year=1997 |isbn=9780226580838 |edition=illustrated |page=321}}</ref> The bark of the lycopsid was somewhat similar to that of ''[[Picea]]'' species, as [[leaf scar]]s formed peg-like projections that stretched and tore as the bark stretched. To resist the bending force of wind, ''Lepidodendron'' depended on their outer bark rather than their vascular tissues, as compared to modern trees that rely mostly on their central mass of wood.<ref name="Students" />