Description: Tufted perennial herbs with short stems.
Leaves basal, tufted; basal sheath red, brown or black, occasionally shiny, forming an open sheath around the stem; lamina linear or terete, glabrous; leaf edge pale or not differentiated; apex attenuate.
Inflorescence with scape flat, subterete or terete, occasionally with tuberculate ribs; bracts rigid, leathery, imbricate with a thickened central region, often with a upper stomatous area, wings thin, basal bracts sterile; flowers solitary in the axils of upper bracts. Outer tepals 3; lateral (outer) pair keeled, bract-like, conduplicate, persistent; upper (inner) one larger, membranous, not persistent. Inner tepals petaloid, yellow [blue or white]; claw c. 3.5 mm long; limb obovate, 5–9 mm long. Anthers 2.2–2.5 mm long. Staminodes conspicuous [or absent], densely hairy along upper margin; hairs 1-seriate, yellow or red, often banded. Ovary 2.5–4.5 mm long; style c. 5 mm long.
Capsule c. 4 mm long; seed oblong, brown with 15–20 red brown ridges when mature.
Distribution and occurrence: World: c. 400 species, tropical to temperate regions. Australia: c. 20 species (c. 17 species endemic), all States. Usually growing in damp or swampy areas, often in heath, in sandy soils.
Text by A. N. L. Doust & B. J. Conn
Taxon concept: B.J. Conn & A.N.L. Doust
| | Key to the species | |
| 1 | Leaves subterete to terete; marginal zone not differentiated from remainder of lamina | 2 |
| Leaves linear, flat; marginal zone pale, silicified, often tuberculate | 4 |
| 2 | Leaves 2.5–30 cm long, basally with minute transverse ridges; capsule not thickened at apex; seeds c. 0.5 mm long; lateral outer tepals with unequal wings | Xyris juncea |
| Leaves 20–90 cm long, basally smooth or striate but not transversely ridged; capsule more or less thickened at apex; seeds ca 1.3 mm long; lateral outer tepals with equal wings
Back to 1 | 3 |
| 3 | Inflorescence ovoid, 10–12 mm diam.; sterile bracts loosely packed, reflexed at base; capsule splitting from base to apex at maturity; lateral outer tepals obovate, keel and wings papillate towards apex, margins apically lacerate | Xyris ustulata |
| Inflorescence obovoid, 6–10 mm diam.; sterile bracts usually tightly packed into more or less 5 vertical rows, not reflexed; capsule splitting in basal two-thirds, apical cap thickened, not splitting; lateral outer tepals ovate, keel with spreading cilia towards apex, margins entire
Back to 2 | Xyris operculata |
| 4 | Capsule walls papery, not thickened towards apex; ovary unilocular; placentation parietal; seeds ovoid to ellipsoid, 0.3–0.6 mm long (section Xyris) | 5 |
| Capsule walls not papery, mostly thickened towards apex; ovary 3-locular or incompletely so; placentation axile; seeds obloid to fusiform, 0.9–1.5 mm long (section Pomatoxyris)
Back to 1 | 6 |
| 5 | Leaves basally with minute transverse ridges; scape subterete to terete, filiform; sterile bracts not keeled; sterile and fertile bracts without a notched apex | Xyris juncea |
| Leaves smooth or striate, basally without transverse ridges; scape flat to subterete, linear; sterile bracts often keeled; sterile and fertile bracts with a notched apex
Back to 4 | Xyris complanata |
| 6 | Inflorescence 2- or 3-flowered, 2.5–3.6 mm diam., with basal pair of sterile bracts (2–3 mm long) shorter than the next more distal pair; leaves 1–1.4 mm wide; seeds 0.9–1.3 mm long | Xyris gracilis |
| Inflorescence 7–10-flowered, 5–6.5 mm diam., with basal pair of sterile bracts (mostly 4–8 mm long) equal to or longer than the next more distal bracts; leaves 1.4–3.5 mm wide; seeds 1.3–1.4 mm long
Back to 4 | Xyris bracteata |
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