Comparative androecium morphogenesis ofSicyos angulatus andSechium edule (Cucurbitaceae)

“Androecium” ofSicyos angulatus andSechium edule is unique in having a solid central column below a head portion with thecae. Its morphogenesis was examined for the two species. The developmental course is composed of two distinct successive phases; (1) establishment of stamen primordia and (2) uplift of the stamen primordia caused by development of a central column below them. In the first phase, there is a difference between the two species; inSicyos angulatus, two bithecal and one monothecal stamen primordia are formed by congenital fusion among preformed five protrsions, whilst inSechium edule, three or four monothecal stamen primordia are formed without fusion. The central column is later produced by intercalary growth in a region below the stamen primordia in both species. Concomitant with central column development, the center of the floral primordium, which was surrounded by the early formed stamen primordia, is raised up to the top of the central column. The central column could be interpreted as a receptacular column, and not as congenitally fused stamen filaments, as currently believed. The “androecium” of the both species is considered an androecium complex, which consists of the stamens and a receptacular column.