The surface of the columella is called the columellar wall. The depressor septi pulls the columella, the septum, and the tip of the nose downwards. The arched columella has a pearly callus. An extension of the sporangiophore called the columella protrudes into the sporangium. The globules migrate to the columella when the sporangium is formed. The columella is smoothish to weakly ridged. The columella is yellowish, smooth and arched. This is in relation to the length between the glabella (between eyebrows) and the columella. The central axis passes through the columella, the central pillar of the shell. Sea turtles have no external ear and only one ear bone, called the columella. Sporangia are supported by a large apophysate columella atop a long stalk, the sporangiophore. There are no folds on the columella, unlike some other genera within the same family. Delos seems to have been a center of chicken breeding (Columella, "De Re Rustica" 8.3.4). The Roman Columella associated the disease with insects from swamps. Cato, Columella, Varro and Palladius wrote handbooks on farming practice.