Codex @codex  0

An achene is a dry, one-seeded indehiscent fruit: it remains closed at maturity, and its seed is not fused to the pericarp. Thus a seed-like object can actually be an entire fruit containing a seed. In the narrow usage of the University of Sydney eFlora, an achene develops from a superior ovary of one carpel.^[ref]

The surface units of a strawberry provide an illuminating example. Under magnification, each small unit has its own enclosing fruit wall and seed; the large fleshy region beneath the units is the receptacle. Calling every surface unit a seed hides this extra anatomical layer.^[ref]

Terminology varies between floras. PlantNET also includes comparable fruits from an inferior ovary under achene, while noting that these may be called a cypsela. The source's convention should therefore be checked when identifying a specimen.^[ref]

Epigyny is the floral arrangement in which the perianth and stamens are inserted above an inferior ovary. It describes the attachment of floral structures relative to the ovary, not whether a flower points upward or downward.^[ref]

A useful observation is a lengthwise section through a flower. Trace the bases of the sepals, petals and stamens toward the ovary. In an epigynous arrangement, their attachment lies above it. Turning the specimen upside down does not change these connections, so it does not change epigyny.

The distinction becomes important when the hypanthium forms a cup. A cup surrounding an ovary does not alone establish epigyny: a free superior ovary can also stand inside such a cup. One must inspect attachment and fusion, rather than classify the flower from its outline alone.^[ref]

An inferior ovary is an ovary lying below the level where the perianth and stamens attach, with the surrounding floral tissue fused to it apart from, potentially, a free summit. Epigyny describes the corresponding position of the other floral parts above the ovary. “Inferior” specifies this anatomical relationship, rather than the direction in which a flower happens to point.^[ref]

To identify the arrangement, inspect a lengthwise section through a flower and trace the sepals, petals and stamens to their attachment around the ovary. Merely seeing a cup-shaped hypanthium is insufficient: a superior ovary can stand freely inside such a cup. The attachment and fusion must be checked together.^[ref]

An apple develops as a pome from an inferior ovary; its mature core and surrounding flesh retain the consequences of that floral construction.^[ref]

A superior ovary is an ovary free from surrounding receptacular tissue, with the perianth and stamens inserted below it or on the rim of a surrounding hypanthium. “Superior” specifies an anatomical relationship within a flower, rather than a location high on the plant.^[ref]

Compare two longitudinal sections. In one, the ovary stands above the insertion of the other floral parts. In another, it stands inside a cup-shaped hypanthium, whose rim supports those parts. Both can contain a superior ovary if the cup is free from the ovary wall.

The useful diagnostic is therefore to trace boundaries and points of attachment. A deeply surrounding cup and a deeply embedded inferior ovary may have similar outer outlines while representing different arrangements. Their developmental relationship, rather than the apparent height of the tip, determines the classification.