Pappus: A modified calyx made up of a ring of fine hairs, scales, or teeth that persist after fertilization and aid the wind dispersal of the fruit, often by forming a parachute-like structure. The pappuses of an inflorescence may form a ‘clock.’*
Pappuses are characteristic of plants in the sunflower family (Asteraceae). A well-known example is the dandelion whose pappuses act as parachutes to carry the seeds on the wind. Pictured above are the seeds of sow thistle, another plant in the sunflower family.
*Tootill, E. (ed.) (1984). The Penguin dictionary of botany. London: Penguin.