A cypsela is a dry, one-seeded indehiscent fruit derived from an inferior ovary, especially characteristic of Asteraceae. The seed remains enclosed by a fruit wall rather than being the whole structure. In the narrower terminology distinguishing it from an achene, a cypsela has an inferior, origin in two carpels.[ref]
Cypsela in the New York Botanical Garden Lecythidaceae glossary. Definition: inferior bicarpellate ovary and Asteraceae
A pappus, when present, forms a crown or plume associated with the cypsela. It comes from the modified calyx, whereas the seed comes from an ovule. These parts can travel together during seed dispersal while retaining different developmental origins.[ref]
Cypsela in the New York Botanical Garden Lecythidaceae glossary. Pappus identified as modified calyx
To see the distinction, imagine removing the enclosing wall of one mature unit: the enclosed seed is a separate anatomical object. Calling the whole unit a seed hides that extra layer. Some floras use achene broadly enough to include these fruits, so the convention of the identifying flora should be checked.[ref]
Glossary of Botanical Terms by PlantNET. Entries achene and cypsela; Figure18Q–R distinguishes superior- and inferior-ovary origins
New to topics? Read the docs here!