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Plants2 - Lepidodendron was a heterosporous tree common in...

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Plants The Lycophytes became even more significant elements of the world's flora during the Carboniferous. These non-seed plants evolved into trees in the fossil genera Lepidodendron and Sigillaria, with heights reaching up to 40 meters and 20-30 meters respectively. Lepidodendron trunks can be over 1 meter in diameter. However, the stems are composed of less wood (secondary xylem) that usually is found in gymnosperm and angiosperm trees. We know much about the anatomy of these coal-age lycopods because of an odd type of preservation known as a coal ball. Coal balls can be peeled and the plants that are anatomically preserved within them laboriously studied to learn the details of cell structure of these coal age plants. Additionally, we have some exceptional petrifactions and compressions that reveal different layers of the plants' structure. Estimates place the bulk, up to 70%, of coal material as being derived from lycophytes.
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Unformatted text preview: Lepidodendron was a heterosporous tree common in coal swamps. As with many large plant fossils, one rarely if ever finds the entire tree preserved intact. Consequently there are a number of fossil plant genera that are "organ taxa" and represent only the leaves (such as Lepidophylloides ), reproductive structures ( Lepidostrobus ), stem ( Lepidodendron ), spores ( Lycospora ), and roots ( Stigmaria ). Lepidodendron had leaves borne spirally on branches that dichotomously forked, with roots also arising spirally from the stigmarian axes, and both small (microspores) and large (megaspores) formed in strobili (a loose type of soft cone). Taylor and Taylor (1993) note that Lepidodendron reached nearly 40 meters in height, with trunks nearly 2 meters in diameter. The trees branched extensively and produced a large number of leaves. that, when they fell from the branches, produced the characteristic leaf scars of the genus....
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