Lepuropetalon and usually face upward. They are large compared to the rest of the plant, 2 to 3mm in diameter with male and female parts both present and functional. The calyx consists of five broad, often unequal sepals that are joined in the lower part to form a floral cup that encloses the lower half of the ovary and is thickened along its fissures to form five ribs. The sepals persist beyond the maturity of the fruit. The petals are scale-like, white and barely visible, on the rim of the floral cup between the sepals, or sometimes absent. They die but
Calyx of Held embryonic calyx formation. One characteristic that distinguishes Eph proteins and their receptors from other signaling systems is their ability to transmit information bidirectionally. Forward and reverse signaling in VCN and MNTB cells is essential for the proper number and formation of VCN and ipsilateral MNTB projections in the calyx. Eph proteins also ensure that while axons pass through the ipsilateral MNTB, branching and final termination of these projections only occur in the contralateral MNTB, possibly because the proteins are only targeted towards specific regions on the axons. Overall, there are two ultrastructural changes that occur in the calyx of Held.