1. (Bot.) (a) 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. (b) A columnlike axis in the capsule of mosses. 2. (Anat.) A term applied to various columnlike parts; as, the columnella, or epipterygoid bone, in the skull of many lizards; the columella of the ear, the bony or cartilaginous rod conne...