Description

Key Characters:

Growth Form: Annual herbs.

Stems: Stems sometimes tinged reddish or yellowish, erect, ascending, or prostrate, 0.6–6(–9) dm long, unbranched or branched, striate, glabrous, rarely with unicellular to multicellular short hairs, especially above.

Roots:

Leaves: Leaves simple. Alternate. Blades ovate to rhombic–ovate, blades 1–8 cm long, 0.6–6 cm wide. Apex usually broad, widely emarginate. Surfaces glabrous, rarely on the lower surfaces with scattered multicellular hairs along the veins. Margins entire or sinuate. Petioles 0.5–10 cm long. Stipules absent.

Flowers: Flowers in slender to stout axillary or terminal spikes, rarely panicles, both sexes mixed throughout the spikes. Bracts and bracteoles whitish, deltate–ovate to lanceolate, membranous, tipped with a short yellow or reddish mucro. Flowers unisexual; plants monoecious. Calyx of 3(4) sepals; sepals green, lanceolate–oblong to spatulate, 0.7–2 mm long, apex subacute, mucronate, apex of pistillate flowers often more blunt. Corolla (petals) absent. Stamens (2)3–5, distinct; anthers dithecal. Ovary superior, 2–3(4)-carpellate, the carpels connate to form a compound, 1-celled ovary; ovule placentation basal, free-central, or rarely apical; style 1, often lobed; stigmas 2–3.

Fruit: Utricles with circumscissile or irregularly dehiscient; or indehiscent; 2–3 beaked at apex; globose to pyriform; compressed; exceeding the sepals; 1.2–2.5 mm long; indehiscent or rupturing irregularly at maturity; the surface smooth; occasionally wrinkled upon drying. Seeds 1 per fruit; the surface usually lustrous; endosperm essentially absent; dark brown to black; shiny; the margins duller; compressed; 1–1.8 mm long; faintly reticulate; minutely punctate–roughened.

Ploidy: 2n = 16; 34

Habitat: Apparently sparingly naturalized in disturbed areas. Cosmopolitan in warmer regions.

Elevation Range: