Description

Key Characters:

Growth Form: Annual herb.

Stems: Stems erect or ascending with watery sap, unbranched or branched from base, 10–60(–80) cm long, glabrous or sparsely pubescent and with scattered, coarse, stinging hairs, hispidulous at nodes.

Roots: Taprooted.

Leaves: Leaves simple. Opposite. Blades elliptic to ovate, (2.5–)4–13 cm long, (0.7–)1.5–5.2 cm wide, often larger toward apex of stem. Surfaces glabrous except with scattered stinging hairs; blades thin. Margins coarsely laciniate–serrate. 3–5-veined. Petioles 0.5– 4.2 cm long. Stipules prominent, lateral, distinct or connate and interpetiolar; oblong, 1–4 mm long.

Flowers: Flowers in axillary, racemose, paniculate or loose clusters but predominantly pistillate, 0.5–2(–2.5) cm long. Flowers unisexual (and the plants monoecious or rarely dioecious). Calyx of staminate flowers deeply 4-lobed, the lobes imbricate, hispid; Calyx of pistillate flowers 4-lobed, 1.5–2.5 mm long in fruit, ± sparsely hispid, margins hispid–ciliate. Corolla (petals) absent. Stamens in staminate flower 4; filaments incurved in bud, elastically reflexed when pollen is shed; anthers dithecal, opening by longitudinal slits. Ovary superior (pistillate flowers), straight, psuedomonomerous, 1-celled; ovule 1, basal; style 1; stigma sessile or nearly so. Staminate pistillode cup-like, ovary vestigial and sterile.

Fruit: Achenes deltoid; 1.5–2.5 mm long; smooth to slightly roughened with punctate dots. Seeds 1 per achene.

Ploidy: 2n = 24; 26; 52

Habitat: Pastures and subalpine forest.

Elevation Range: 790–2290 m.