Description: Annual or perennial herbs, stems striate and often woody near the base.
Inflorescence terminal racemes or spikes. Flowers usually in groups in axils of bracts. Hypanthium cup-shaped. Petals free at base, fused in the middle, distally free. Stamens 5, 3 long, 2 short, enclosed in the corolla tube; filaments as long as or longer than glandless anthers; pollen reticulate. Ovary of 3–5 carpels; style without membranous cup; stigmatic lobes 3–5, spreading.
Fruit a schizocarp; cocci 1–5, wingless or 3-winged, connected at base to column by short triangular point of attachment, leaving a triangular scar after shedding; wings lacking prominent transverse veins; style inserted between and shorter than mature cocci.
Distribution and occurrence: World: 14 species, Malesia, Micronesia, Australia, New Zealand. Australia: 13 species (12 species endemic), all States.
Text by A. K. Brooks. Key updated by Kerry Gibbons, from Barker, W.R., Flora of Australia Online [accessed 17 May 2023].
Taxon concept:
| | Key to the species | |
| 1 | Flowers solitary, in uppermost leaf axils; prostrate herb, forming mats | Stackhousia pulvinaris |
| Flowers in terminal inflorescence, several- to many-flowered, erect herbs | 2 |
| 2 | Flowers arranged singly along the inflorescence axis; 1–3 bracts at each main inflorescence node | 3 |
| Flowers in clusters of 1–6 along the inflorescence axis; 3–12 or more bracts at each main inflorescence node
Back to 1 | 4 |
| 3 | Leaves spathulate, rounded at apex; cocci prominently winged | Stackhousia spathulata |
| Leaves obovate to linear or lanceolate, acute; cocci not winged
Back to 2 | Stackhousia monogyna |
| 4 | Cocci pyriform to dumbbell-shaped, muricate at apex, with a prominent round basal cavity; leaves linear, 1–2.5 mm wide | Stackhousia muricata |
| Cocci obovoid, wrinkled to reticulate, rarely muricate at apex, the basal cavity lacking or shallow and ovate to narrow-triangular; leaves narrow-obovate to elliptic, 1.5–8 mm wide or reduced to scales
Back to 2 | 5 |
| 5 | Leaves foliose, the broadest 1.6–7.5 mm wide, the basal ones sometimes reduced to scales | Stackhousia viminea |
| Leaves reduced to scales, rarely (S. clementii) foliose, less than 1.6 mm wide
Back to 4 | 6 |
| 6 | Cocci 1–3, obloid-ellipsoidal, rugose to tuberculate; inflorescence 1-sided | Stackhousia nuda |
| Cocci usually 1, curved-obovoid, rugose-reticulate, sometimes muricate in apical part; inflorescence cylindrical
Back to 5 | Stackhousia clementii |
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