Practice question

In Asteraceae each floret develops on a flattened receptacle surrounded by involucre of bracts, calyx does not form typical green sepals but metamorphoses into pappus comprising bristles, scales or plumose hairs crowning the inferior ovary. Ontogenetically a ring primordium at corolla base expresses sepal identity genes, considered modified calyx acting for fruit dispersal by wind or epizoochory. Petals form ligulate or tubular corolla, stamens syngenesious, bracts form involucre. Thus pappus homology as calyx derivative explains absence of conventional sepals in sunflower cypsela and functional replacement by dispersal apparatus.