The developmental floral morphology of Montrichardia arborescens (Araceae) revisited

The spadix of M. arborescens has a cylindrical or ellipsoid form at maturity and contains unisexual flowers without a perianth. The pistillate and staminate flowers are located in the basal and apical portions, respectively, of the inflorescence. In the upper portion of the female zone, there is a row of poorly developed female flower primordia. Above the row of underdeveloped gynoecia, there is a row of atypical flowers. On the side facing the female zone, primordia are absent on the floral meristem whereas 1 to 3 stamen primordia are present on the side facing the male zone. The presence of male appendages (stamens) and vestigial female appendages (portion of the ovary) on the same whorl indicates that these atypical flowers may correspond more appropriately to the Philodendron type compared to the Cercestis type where the staminodes and ovary are inserted in 2 distinct whorls. Morphologically, the structure of the atypical flowers in the inflorescences of Montrichardia is much closer to the Philodendron type than the Cercestis type. However, the female portion of the bisexual flowers is fully developed in Philodendron in contrast to Montrichardia where the gynoecial portion remains vestigial.