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
Taxa not yet included in identification key
| ||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|
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|3||Leaves spathulate, rounded at apex; cocci prominently winged||Stackhousia spathulata|
|Leaves obovate to linear or lanceolate, acute; cocci not winged|
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|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|
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|5||Leaves foliose, 1.6–7.5 mm wide, the basal ones sometimes reduced to scales||Stackhousia viminea|
|Leaves reduced to scales, less than 1.6 mm wide|
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