Description

Key Characters:

Growth Form: Prostrate annual herbs.

Stems: Stems up to ca.10 dm long.

Roots:

Leaves: Leaves compound. Opposite. Blades oblong to ovate or elliptic, 1–4.5 cm long, leaflets 3–6(–8) pairs, 4–11 mm long, 2–4 mm wide. Surfaces moderately to densely sericeous to long strigose, especially when young. Margins entire. Petiolate. Stipules subulate, 2–5 mm long.

Flowers: Flowers in peduncles densely antrorsely strigose and hirsute, the latter hair type with pustulate bases. Flowers bisexual (perfect), actinomorphic. Calyx of 5 sepals; sepals ovate to lanceolate, equal, 2–4.5 mm long, 1.5–2 mm wide, margins scarious. Corolla of 5 petals; petals yellow, oblong to obovate, 3–5 mm long, 1–3 mm wide. Stamens 10, in 2 whorls of 5, the outer whorl opposite the sepals and adnate to them basally, usually slightly longer than inner whorl; filaments filiform or subulate, without appendages; anthers cordate to sagittate. Ovary superior, long–strigose.

Fruit: Fruit 5–12 mm in diameter; mericarps dorsally crested and tuberculate; bearing 2 stout hard spines 2.5–7 mm long; sometimes also with 2 smaller ones near base; the crests short hirsute; the hairs with pustulate bases. Seeds oblong–ovoid; seed coat membranous; embryo straight; endosperm absent.

Ploidy: 2n = 12; 24; 32; 36; 48

Habitat: Disturbed areas such as along roadsides; often in sandy soil.

Elevation Range: 0–15 m.