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Hydrasperma tenuis ovules containing cellular megagametophytes have been recovered from Upper Devonian (stage) strata near Ballyheigue, County Kerry, Ireland. The megagametophytes are elliptical in transverse section and obovate in longitudinal section. The vegetative cells are organized into three, distinct, concentric zones and exhibit the radial orientation characteristic of centripetal development. Up to three archegonia may be present at the apical end of the megagametophyte. They are elliptic to terete in cross‐section and elliptic in longitudinal section. Archegonia are thought to be sunken with each possessing a canal‐like connection to the surface of the megagametophyte. Archegonial jacket cells surround the egg cavity. A low, broad tent‐pole occurs at the top of the megagametophyte. This report represents the oldest, structurally‐preserved gymnosperm megagametophyte.

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