Plants1 - Plants Cross section through a...

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Plants Cross section through a branch (approximately an inch in diameter) of a large lepidodendrid tree. In the very center is a pith, surrounded by primary xylem and a small fringe of secondary xylem [wood, MJF]. Then there is black gunk and an open white area. Phloem and innermost cortical tissues are typically not well preserved, and this black gunk and white areas probably represent their positions in the branch. The outermost part of the stem is gone.
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Lepidodendron was a large Carboniferous tree reaching heights of 100 feet. When the plant's leaves fell they left diamond-shaped scars arranged in oblique rows around the stem. Sigillaria was another arborescent lycopod, and is also common in coals-age deposits. In contrast to the spirally borne leaves of Lepidodendron , Sigillaria had leaved arranged in vertical rows along the stem. Like the lycophytes, the sphenophytes reached their zenith during the Carboniferous and have declined to but a single genus, Equisetum, surviving today. The largest of the
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Plants1 - Plants Cross section through a...

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