Description

Key Characters:

Growth Form: Annual or perennial herbs.

Stems: Stems diffuse, creeping to erect, branched.

Roots:

Leaves: Leaves simple. Opposite. Members of a pair sometimes unequal. Margins entire or toothed. Veins obscure or palmately 3-veined. Petiolate. Stipules connate.

Flowers: Flowers in axillary cymes, these solitary or in dense, head-like or open, paniculate inflorescences, bracts small, inconspicuous. Flowers unisexual (and the plants monoecious or dioecious). Calyx of staminate flowers lobes (2–)4, concave, subvalvate, usually mucronate or appendaged on back, pistillate Calyx lobes (2)3, 1 lobe larger than others and usually gibbous or hooded, staminodes minute, opposite the Calyx lobes, scale-like. Corolla (petals) absent. Stamens (2–)4, pistillode conical or oblong. Ovary superior (pistillate flowers), straight, psuedomonomerous, 1-celled; ovule 1, basal; style 1; stigma sessile, minutely penicillate; staminate flower ovary vestigial and sterile.

Fruit: Achenes ovoid; compressed; smooth or roughened with microscopic papillae; sometimes partly enclosed by the large calyx lobe; often forcefully ejected from it by the staminodes. Seeds 1 per achene; with scarcely any endosperm; cotyledons broad.

Ploidy:

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