Erect annual, 2.5–7 cm tall, simple or branched towards base; stems quadrangular, glabrous to slightly minutely pubescent below, rigid. Basal leaves clustered, linear-spatulate, 4–7(–12) mm long, 1 mm wide, narrowing into a petiole-like base, apex obtuse, margins entire, subglabrous or minutely pubescent; cauline leaves opposite, narrowly elliptic to almost linear, 1.5–5 mm long, 0.8­–1 mm wide, acute to subobtuse, margins entire, subglabrous, venation markedly prominent beneath. Flowers solitary, axillary; pedicels up to 10 mm long, slender, glabrous to minutely pubescent. Calyx (1.6–)3–4 mm long, glabrous to minutely glandular-pubescent, somewhat prominently ribbed; lobes deltate, 0.5–1.2 mm long, acute or obtuse, glabrous on margins or minutely ciliate. Corolla various shades of blue and white, (3.5–)5–7(–8) mm long; upper lip bifid; lower lip 3-lobed, lobes rounded; tube ± 3–4 mm long, externally glabrous. Stamens 2, fertile; filaments up to ± 1 mm long; staminodes 2, clavate, 0.3–0.5 mm long, erect or more frequently slightly curved outwards, sparsely to densely clothed with minute clavate hairs which extend to palate between staminodes, short antero-lateral ridges barely evident. Capsule elliptic-ovate in outline, 3.5–6 mm long, 1.5­–2 mm broad, acute.