an axis to which a carpel of a compound pistil may be attached, as in the case of the geranium; or which is left when a pod opens.-a columnlike axis in the capsules of mosses.-a term applied to various columnlike parts; as, the columella, or epipterygoid bone, in the skull of many lizards; the columella of the ear, the bony or cartilaginous rod connecting the tympanic membrane with the internal ear.-the upright pillar in the axis of most univalve shells.-the central pillar or axis of the calicles of certain corals.