Lepidodendron The Fossil Plant Genus
Lepidodendron, derived from Greek words lepido meaning scale and Dendron meaning tree, hence commonly known as scale trees are an extinct genus of primitive vascular tree like plants belonging to the family of Lycopsids (club mosses). This black color fossil formed a part of the coral forest flora.
An account of what Lepidodendron looked like
One of the most interesting fossils found in Carboniferous shales and coal deposits, Lepidodendron was a tree with tall, thick trunk topped with a circles of bifurcating branches that bore leaves in clusters, they were long and slender and had spiral arrangement. Unlike the non-photosynthetic brown bark of modern day trees, Lepidodendron had a green trunk. It was thought to be a giant herb, its trunk supported by a thick rigid structure, a bark like region, which surrounds it and grows along but did not peel off as we notice in most trees existing today. These fossil plants grew tall, about 40 metres in height and 2 metres in diameter.
Found in the wettest parts of the coal swamps that may have existed during the Carboniferous period, Lepidodendron grew in dense regions, as many as 1000 to 2000 club mosses existing per hectare of land. This could be true since they did not branch until they fully grow and possibly would have spent most time of their lives as un-branched poles.
Reproduction took place through spores
The branches of this plant didn’t produce seeds; on the contrary they reproduce rapidly by the process of spore formation. By the onset of the Mesozoic era, it is believed that most of the giant lycopsids, inclusive of Lepidodendron, died out, probably because of the competition from emerging smaller Quillworts. Most of the species were monocarpic, as believed which means that they reproduced only once and that too when they approach the end of their life cycle.
The life cycle of Lepidodendron plant
During the young stages of plant growth, Lepidodendron grew as non-divided trunks with long, narrow leaves emerging out from the growing tip. At later stages, trunks start to bear branches, either dichotomy formed at the tip or lateral branches that were later dropped off. After the branching process, leaves shrink and appear awl shaped. As the plant continued to grow, it shed leaves from the worn out parts of its stem that left leaf bases shaped like diamond.
As discussed above, the stem or the trunk was distinguished by the thin central string of wood and bore a thick bark support around it that grew thicker as time passed. The underground parts of the plant, termed as Stigmaria were in close resemblance with modern day stems and thus not classified as true roots. The shape of the leaf base that formed when leaves were discarded and the layout of their vascular strands/strings were the major factors, which help, distinguish the different species within the group of arborescent lycopsids, the family to which Lepidendron belongs.
References:
- Davis, Paul; Kenrick, Paul (2004), Fossil Plants, Washington, DC: Smithsonian Books, ISBN 1-58834-181-X
- Morran, Robin C. (2004). A Natural History of Ferns, Portland: Timber Press. ISBN 0-88192-667-1
