Floral Anatomy of Calliandra

Floral anatomy of six species of Calliandra (C. haematocephala, C. portoricensis, C. fasciculata, C. harrisii, C. selloi and C. houstoniana) has been studied. Sepals are one or three traced and petals are single traced. Branching of traces results into variable number of bundles in calyx and corolla tubes. Stamens are numerous arranged in one or two rings and each is single traced. A prominent disc with well developed vascular tissue is observed surrounding the stalk of the ovary in C. haematocephala, C. portoricensis, C. harrisii and C. houstoniana. Vasculature of the gynoecium consists of two carpellary ventral bundles, supplying the ovules arranged on marginal placenta, and one carpellary dorsal bundle. From the vascular supply and position, the disc is considered to be staminal. Because of three traced sepals, free petals, numerous stamens, more than 2 rings of staminal traces and a well developed disc, C. houstoniana appears to be less advanced than the other five species, while C. fasciculata with the minimum number of stamens arranged only in single ring with well defined corolla stamen tube and without a distinct disc may be considered the most advanced out of all.