STAMINATE FLORAL DEVELOPMENT IN BEGONIA-CUCULLATA VAR HOOKERI AND 3 DOUBLE-FLOWERING BEGONIA CULTIVARS, EXAMPLES OF HOMEOSIS

Homeosis is a process whereby features characteristic of one structure are found in the position that a different structure normally occupie s. In three double-flowering begonia cultivars, perianth features are expressed in the positions stamens occupy in a single-flowering begoni a. The staminate flower of Begonia cucullata var. hookeri (Willd.) con sists of two broad sepals, two small petals in a more or less decussat e arrangement, and an androecium of numerous stamens. The staminate fl owers of Begonia semperflorens-cultorum 'Cinderella', 'Goldie Locks', and 'Lucy Lockett' also have a perianth of two sepals and two petals, but sepaloid and petaloid appendages form in positions that stamens oc cupy in the single-flowered progenitor. Using epi-illumination microsc opy, we found that early stages of floral development in the double-fl owering cultivars are similar to the early stages of development in th e single-flowered begonia, while later stages diverge remarkably. The first primordia that will form petaloid appendages are small and round at the time of initiation, similar in appearance and position to thos e primordia that become stamens in the single-flowered begonia. As the se primordia develop, they broaden and flatten, forming perianth-like appendages.