A paleocene plant fossil from the Sentinel Butte Formation.A stem fossil from the Sentinel Butte Formation (North Dakota) was investigated using brightfield and scanning electron microscopy. Within the surface periderm Periderm A group of tissues which replaces the epidermis in the plant body. Its main function is to protect the underlying tissues from desiccation, freezing, heat injury, mechanical destruction, and disease. are vertically oriented fiber masses whose individual cells overlap. Centripetal to the fibers is a circle of vascular bundles separated by multiseriate rays. The bundles encircle the pith. Many cells throughout the stem contain fungal hyphae hy·pha n. pl. hy·phae Any of the threadlike filaments forming the mycelium of a fungus. [New Latin, from Greek huph which can pass from cell to cell across cell wall regions. The hyphae are septate septate /sep·tate/ (sep´tat) divided by a septum. sep·tate adj. Divided by a septum or septa. septate divided by a septum or septa. and probably represent signs of incipient decay of the stem prior to fossilization. The water-conducting tissue (xylem) consists of cells with annualar/helical thickenings or pits. The pits are present in opposite or scalariform arrangements. The water-conducting cells are probably tracheids and the architecture of the xylem in general is similar to that of the extant family Trochodendraceae. Roland Dute and Michael Miller, Dept. Biological Sciences, Auburn Univ., Auburn, AL 36849. Ronald Lewis, Dept. of Geology and Geography, Auburn, Univ., Auburn, AL 36849. |
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