| Name | Structure/ Category | Description |
|---|---|---|
| Achene | [Fruits] {type} | A more or less small, dry fruit that does not split open at maturity (indehiscent), with a typically thin, close-fitting wall surrounding a single seed. |
| Acicular | [Leaflets, Leaves] {shape} | Very long and slender, gradually tapering to a point, like a needle; needle-shaped. |
| Acorn | [Fruits] {type} | A nut with a persistent, cup-like structure (cupule) attached at the base consisting of numerous partially fused, overlapping, dry bracts, as in oaks (Quercus). |
| Actinomorphic | radially symmetrical -- used of organisms, organs, or parts capable of division into essentially symmetrical; halves by any longitudinal palne passing through the axis | |
| Acuminate | [Leaf apices, Leaflet apices, Petal apices, Phyllary apices, Sepal apices] {shape} | Gradually tapering to a sharp point, forming concave sides along the tip. |
| Acute | [Leaf apices, Leaflet apices, Petal apices, Phyllary apices, Sepal apices] {shape} | Tapering to a pointed apex with more or less straight sides, the sides coming together at an angle of less than 90. |
| Adnate | grown together, used especially of unlike parts | |
| Adventitious | (1) Structures or organs arising in a position that is unusual for their type, as roots originating on the stem. | |
| Adventitious | (2) [Roots] {type} | Roots arising from any part of the plant (e.g. stem or leaf) other than the root system; usually growing laterally, often from the lower part of the main stem. |
| Aerial stem | [Stems] {type} | A prostrate to erect, above ground stem. |
