Glossary of plant morphology flowers, a tube or cup-like hypanthium (floral tube) is formed above or around the ovary and bears the sepals, petals, and stamens. There may also be a nectary producing nectar. Nectaries may develop on or in the perianth, receptacle, androecium (stamens), or gynoecium. In some flowers nectar may be produced on nectariferous disks. Disks may arise from the receptable and are doughnut- or disk-shaped. They may also surround the stamens (extrastaminal), be at the stamen bases (staminal), or be inside the stamina (intrastaminal). Finally, the actual reproductive parts form the innermost layers of the flower. These leaf primordia become specialised
Calyx of Held high frequency sound localization. This synapse has been described as the largest in the brain. The related endbulb of Held is also a large axon terminal smaller synapse (15-30 µm in diameter) found in other auditory brainstem structures, namely the cochlear nucleus. As with the calyces, these synapses promote fast, efficient information transfer. The calyx of Held holds vesicles containing glutamate on the presynaptic terminal, the vesicles are released upon stimulation (originating in the auditory system). The glutamate then binds to two known glutamate receptors, AMPA- and NMDA receptors. Commonly used in research due to its large size, the calyx