Inflorescence and flower development in the hedychieae (Zingiberaceae): Scaphochlamys kunstleri (Baker) holttum

Primary inflorescence bracts are initiated in a spiral phyllotactic pattern on the flanks of the inflorescence apex. A cincinnus primordium forms in the axil of each primary bract. A prophyll is initiated in the transverse plane and later extends around the periphery of the cincinnus to produce a sheathing, but not tubular, bract. The apex of the cincinnus forms a flower. Flower development begins with the enlargement and flattening of the floral apex. Sepal initiation is sequential but differs in the first two flowers of a cincinnus. The different sequences are likely the result of developmental constraints that operate at the time of sepal initiation. After initiation, the margins of the sepals become confluent and intercalary growth produces the synsepalous calyx. The periphery of the flower, interior to the sepals, now rises to form a ring primordium composed of three common petal/androecial primordia. The common primordia enlarge, flatten, and separate to produce a petal to the exterior and an androecial member to the interior. The outer androecium forms in the regions of the ring primordium left vacant by the formation of the other floral parts. The anterior outer androecial member soon ceases growth and contributes only initially to the formation of the labellum. The gynoecium shows heterochrony in its time of initiation, which occurs much earlier than in other species of Zingiberaceae. Gynoecial initiation takes place on the margins of the central flora cup, at the time of the separation of the common primordia. Three gynoecial primordia from in antipetalous positions. Septa development differs in the basal and apical portions of the ovary. At the base, the primordia grow inward and fuse to form the central axis of the ovary. At the apex, there is little radial growth of the primordia. They cease growth soon after initiation and produce a unilocular cavity. Ovules form at the junction of these two regions and project up into the cavity. Epigynous nectaries form after all other floral organs.