Description

Key Characters:

Growth Form: Nearly glabrous annual herbs.

Stems: Stems ascending or spreading, 3–5 dm iong, spongy when growing in water.

Roots:

Leaves: Leaves simple. Opposite. Blades linear–oblong to linear–lanceolate, 2–10 cm long, 0.3–1.5 cm wide. Base cuneate, truncate, or auriculate. Surfaces glaucescent. Margins entire. Sessile. Stipules minute or absent.

Flowers: Flowers small, usually 3–5 in axillary cymes, peduncles 3–5 mm long, always longer than pedicels. Flowers small, bisexual (perfect), sometimes cleistogamous flowers also present, actinomorphic or sometimes zygomorphic. Calyx teeth 4, usually with a small horn-shaped appendage in each sinus, valvate, appearing as lobes on the floral tube, often alternating with external appendages at the sinuses. Corolla of 4 petals, alternate with the sepals, distinct, attached at summit of or within floral tube, crumbled in bud, small, purple to pink, 1–2 mm long, caducous, sometimes absent. Stamens 4–8, inserted at various levels on the floral tube; anthers dithecal, opening by longitudinal slits. Ovary superior, 2–4(–6)-carpellate, with as many cells, at least at base, rarely 1-celled, placentation axile, rarely parietal when 1-celled; ovules 2 to numerous, anatropous, ascending; style 1, persistent, 1.5–3 mm long; stigma usually capitate.

Fruit: Capsules ca. 4 mm long; enclosed by the persistent floral tube when mature; 2–4–celled; dehiscing irregularly. Seeds numerous; angled and minutely pitted; endosperm absent or very scanty.

Ploidy: 2n = 30–32; 66

Habitat: Sparingly naturalized in wet sites such as taro paddies.

Elevation Range: