Syngenesious stamens are seen in
Syngenesious condition denotes anthers laterally united into a tube encircling style while filaments remain free and distinct. Cohesion results from interlocking epidermal hairs, enabling precise secondary pollen presentation mechanism as elongating style brushes pollen outward. Found characteristically in Asteraceae including Helianthus, Tagetes and Tridax. Fabaceae shows diadelphous filaments fused, Solanaceae epipetalous free anthers, Malvaceae monadelphous filament column. Syngenesious anthers together with inferior ovary, pappus and cypsela form synapomorphy for Asteroideae subfamily, enhancing pollen economy and insect mediated pollination efficiency in head inflorescence.
Ref: Bhattacharya, Systematic Botany; Campbell Biology 12th ed., Syngenesious Asteraceae and pollination