Overview of
Lepidodendron lycophytes|370x370px , which from left to right include
Lepidophloios, Synchysidendron, Diaphorodendron and
Sigillaria. Lepidodendron species were comparable in size to modern trees. The plants had tapering trunks as wide as at their base that rose to about and even , arising from an underground system of horizontally spreading branches that were covered with many rootlets. Though the height of the lycopsids make the plants similar to modern trees, the constant
dichotomy of branches created a
habit that contrasts with that of modern trees. At the ends of branches were oval-shaped
strobili called
Lepidostrobus that had a similar shape to modern cones of a
spruce or
fir.
Stem The stem of the lycopsids had a
unifacial vascular cambium, contrasting with the
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
cortical meristem. The nearly-uniform growth of this cortical tissue indicates no difference in growth during changing seasons, and the absence of dormant
buds further indicates the lack of
seasonality in
Lepidodendron species. The bark of the lycopsid was somewhat similar to that of
Picea species, as
leaf scars 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.
Hyphae are occasionally present in the tissues of
Lepidodendron lycopsids, indicating the presence of
mycorrhizal associations.
Decay .|213x213px Different
fossil genera have been described to name the various levels of decay in
Lepidodendron bark fossils. The name
Bergeria describes stems that have lost their epidermises,
Aspidiaria is used when cushions have been removed by deep decay, and
Knorria is used when the leaf cushions and the majority of cortical tissues has decayed, with a shallow "fluted" surface remaining. However, it has been suggested that these are more likely growth forms than preserved bark types, as entire fossilized trunks have been discovered with dissimilar forms; if decay is assumed to be constant throughout the trunk, then different forms indicate growth rather than levels of decay. It is likely that the trunk of
Lepidodendron lycopsids were subject to the growth forms
Knorria,
Aspidiaria, and
Bergeria progressing up the trunk, respectively. ==Growth and reproduction==