Synonyms: Zygophyllum pro parte APNI*
Description: Annual herbs or perennial subshrubs with fleshy branches and leaves, glabrous or almost so.
Leaves opposite, usually petiolate, with 1 pair [or rarely several pairs] of leaflets, or sessile and simple, [linear or] apically 2-lobed.
Flowers solitary, axillary, usually pedicellate. Sepals 4 or 5, imbricate, with green centre and membranous margins. Petals 4 or 5, rarely 3 or 6, imbricate, clawed, yellow, white or orange [rarely red]. Stamens 4, 6, 8 or 10. Disc between stamens and ovary sinuate or distinctly 3–5-lobed or 3–5-partite, the lobes at base of septa that separate the loculi of the ovary. Ovary 3–5-locular, 3–5-angled; style subulate; stigma ± globose or lobed.
Fruit a 4- or 5-angled loculicidal capsule, or indehiscent and with 3 or 4 vertical wings, or breaking into 2 or 4 dorsally winged cocci; seeds with endosperm, 1–6 per loculus, often mucilaginous when wet.
Distribution and occurrence: World: c. 150 species, Mediterranean to C Asia, southern Africa & Australia, in deserts and steppes. Australia: c. 30 species, all mainland States and Bass Strait islands.
Roepera includes species previously included in Zygophyllum. All Australian species are now included in Roepera (RM Barker, Fl. Aust. 26, 2013, edited K.L. Gibbons Aug 2019).
Text by Hj. Eichler (1992); edited KL Wilson (Jan 2014) and K.L.Gibbons (Aug 2019).
Taxon concept: Beier, B.-A., Chase, M.W. & Thulin, M. (2003), Phylogenetic relationships and taxonomy of subfamily Zygophylloideae (Zygophyllaceae) based on molecular and morphological data. Plant Systematics and Evolution 240, 11–39
Taxa not yet included in identification key
Roepera compressa
| | Key to the species | |
| 1 | Fruit 3- or 4-winged, more or less globose in outline, indehiscent or septicidally breaking into up to 4 cocci; filaments without wings or appendages in lower part | 2 |
| Fruits 4- or 5-angled, more or less globose or obovoid to cylindrical, loculicidal; filaments in lower part often winged or with more or less stipular appendages | 4 |
| 2 | Fruit 3-winged; stamens 6; leaves sessile, cuneate, with 2 short broad obtuse lobes at apex, upper pairs fused at base; annual | Roepera howittii |
| Fruit 4-winged; stamens 8; leaves petiolate, with 1 pair of linear leaflets, upper pairs not fused; mostly perennial
Back to 1 | 3 |
| 3 | Petals obovate, obtuse or faintly notched at apex, golden-yellow; fruit 12–18 mm long, splitting into 2–4 cocci when ripe; seeds usually 1 (rarely 2) in each coccus | Roepera aurantiaca |
| Petals narrow-oblanceolate, more or less acute at apex, pale lemon-yellow; fruit 8–12 mm long, indehiscent; seeds usually only 1 in each fruit
Back to 2 | Roepera eremaea |
| 4 | Capsule 5-locular, 5-angled; flowers 5-merous; stamens 10 | 5 |
| Capsule 4-locular, 4-angled; flowers 4-merous; stamens 8 or 4
Back to 1 | 6 |
| 5 | Capsule truncate at apex, with a short blunt appendage at upper corner of each angle, more or less turbinate; perennial, woody at base | Roepera apiculata |
| Capsule rounded at apex, without appendages at the angles, more or less globose; herbaceous annual
Back to 4 | Roepera iodocarpa |
| 6 | Capsule almost sessile, often more or less erect, narrow-cylindrical to narrow-ellipsoidal, with 4 erect thick appendages at apex | Roepera prismatotheca |
| Capsule distinctly pedicellate, drooping, broader, without erect appendages at apex
Back to 4 | 7 |
| 7 | Leaflets usually crenate at apex (i.e. with 3 blunt teeth); annual | Roepera crenata |
| Leaflets entire or notched at apex; annual or perennial
Back to 6 | 8 |
| 8 | Capsule truncate at apex | 9 |
| Capsule rounded at apex; annual
Back to 7 | 13 |
| 9 | Perennial; capsule 6–11 mm long; petals yellow | 10 |
| Annual; capsule 5–7 mm long; petals yellow or white
Back to 8 | 11 |
| 10 | Leaflets continuous from petiole; petals obovate, 9–12 mm long, longer than the sepals; shrub with more or less self-supporting stems and branches | Roepera confluens |
| Leaflets articulate at base; petals narrow-obovate to elliptic, 4–8 mm long, scarcely exceeding the sepals; shrub with very slender stems and branches, usually leaning on stronger bushes
Back to 9 | Roepera angustifolia |
| 11 | Petals yellow; at least some filaments with stipular appendages in lower part; leaflets mostly cuneate and distinctly emarginate at apex; capsule broader than long; stamens 8 | Roepera emarginata |
| Petals white; filaments usually broadened in lower part, without stipular appendages; leaflets linear to narrow-oblong rounded or truncate (rarely slightly emarginate) at apex; capsule usually more or less longer than broad; stamens 8 or 4
Back to 9 | 12 |
| 12 | Stamens 4; petals narrow-obovate to narrow-elliptic, usually as long as or slightly longer than petals; seeds 3 or 4 per loculus; leaflets narrow-oblong, more or less abruptly truncate, sometimes rounded to almost emarginate at apex | Roepera ammophila |
| Stamens 8; petals cuneate, shorter than to as long as sepals, more or less 3-lobed at apex; seed 1–2 per loculus; leaflets very narrow-obovate, rounded at apex
Back to 11 | Roepera similis |
| 13 | Petals white, usually shorter than sepals; capsule ellipsoidal, c. 8 mm long; leaflets continuous from petiole; seeds usually 2 per loculus | Roepera ovata |
| 13 | Petals white, usually shorter than sepals; capsule ellipsoidal, c. 8 mm long; leaflets continuous from petiole; seeds usually 2 per loculus | Roepera ovata |
| Petals yellow, longer than sepals; capsule subglobose and very small or oblong-ovoid and more than 10 mm long; leaflets continuous from petiole or articulate at base; seeds 1, 3 or 4 per loculus
Back to 8 | 14 |
| 14 | Capsule subglobose, 3–4 mm long; 1 seed per loculus; leaflets not articulate, cuneate to more or less oblong, ± 1 cm long, mostly notched at apex; petals c. 3 mm long | Roepera humillima |
| Capsule oblong-ovoid to oblong-obovoid, 14–18 mm long; usually 3 or 4 seeds per loculus; leaflets articulate at base, obliquely obovate, 1–4 cm long, rounded at apex; petals 8–15 mm long
Back to 13 | Roepera glauca |
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