Delevoeyas, Theodore. (Yale U., New Haven, Conn.) Investigations of North American cycadeoids: cones of Cycadeoidea. Amer. Jour. Bot. 50(1): 45–52. Illus. 1963.—A reinvestigation of the morphology of cones of Cycadeoidea indicates that they did not expand into flower‐like structures at maturity The microsporangiate region was actually a compound synangium fused peripherally and, for at least part of the time, along the inner surface surrounding the ovulate receptacle. Capping the microsporangiate region is a massive parenchymatous dome. Synangia were borne along trabecular structures which connected the outer part of the microsporangiate structure to the inner face. Pollen may have been released after an abscission of the entire compound synangium.
Silicified stems with typical cycadalean anatomy are described from specimens collected from the Fremouw Formation (Triassic) in the Transantarctic Mountains of Antarctica. Axes are slender with a large parenchymatous pith and cortex separated by a narrow ring of vascular tissue. Mucilage canals are present in both pith and cortex. Vascular tissue consists of endarch primary xylem, a narrow band of secondary xylem tracheids, cambial zone, and region of secondary phloem. Vascular bundles contain uni‐ to triseriate rays with larger rays up to 2 mm wide separating the individual bundles. Pitting on primary xylem elements ranges from helical to scalariform; secondary xylem tracheids exhibit alternate circular bordered pits. Traces, often accompanied by a mucilage canal, extend out through the large rays into the cortex where some assume a girdling configuration. A zone of periderm is present at the periphery of the stem. Large and small roots are attached to the stem and are conspicuous in the surrounding matrix. The anatomy of the Antarctic cycad is compared with that of other fossil and extant cycadalean stems.
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