Lepidodendron(redirected from Giant clubmosses)
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a genus of fossil arborescent lycopods (club mosses). Lepidodendrons existed during the Carboniferous and Permian periods in the tropical zone (for example, the Euramerican paleobotanical region). These plants had a straight trunk that branched dichotomously in the upper part; the trunk measured up to 20–30 m tall and had a diameter of up to 2 m at its base. The trunk consisted of wood and a thick bark that was covered with spiral rows of cushions. The cushions varied in shape from fusiform to rhombic or rounded-elliptic. The upper half of each cushion has a scar from a fallen leaf; over the scar is a pit that enclosed a ligule, whose function is not clear. In contrast to the bark of modern plants, the bark of Lepidodendron was not shed as the trunk grew but increased in thickness. In order to facilitate transpiration in a hot and humid climate, the bark was equipped with strands of air-bearing tissue. Below the level of the soil the trunk of Lepidodendron branched dichotomously, forming rhizophores (stigmariae), from which delicate roots emerged. The leaves, which bore sporangia (sporophylls), were gathered into large, heterosporous cones.
V. A. VAKHRAMEEV