In some fronds the pinna are further divided into segments, creating a bipinnate frond. The "koru" symbol is inspired by the shape of an unfurling silver fern frond. A leaf gap is where the vascular tissue branches off to a frond. The fiber is produced from the membrane on the underside of each individual frond leaf. A frond is a large, divided leaf. Left on the plant, each fiddlehead would unroll into a new frond (circinate vernation). Sporangia are formed in sori on the underside of the frond. Underneath the shield are gold wheat ears and a palm frond. Local Acacia with palm frond matts was used for the ceiling of the palace. Lulav (; ) is a closed frond of the date palm tree. Mr. Ihle built a temporary palmetto frond shelter. The primary symbols of Ogun are Iron, the dog, and the palm frond. Blade division decreases towards the apex of the frond. The margin is smooth and the frond is dichotomously branched. Some attributes are general, such as the palm frond carried by martyrs.