General: Annual herb from a taproot; stems prostrate to decumbent, often branched at base, straight appressed-hairy, 2-25 cm long.
Leaves: Basal and stem leaves linear, to 2 cm long and 2 mm wide, appressed-hairy to spreading-hairy, entire, mostly alternate, reduced towards the branch tips.
Flowers: In small clusters along and at tips of stems; corollas tiny (to 3 mm long), white, tubular at base, flaring merely 1 mm wide or less at top.
Fruits: Nutlets usually 4, spreading in pairs, oblong, 1.5-2 mm long, flattened and sunken in the centre, with prominent, upturned or incurved margins beset (mostly above the middle) with hooked prickles.