Cycloloma

Herbs, annual, polygamo-monoecious, villose or tomentulose, becoming glabrous at maturity. Stems erect, much branched, especially in inflorescence, not jointed, not armed, not fleshy. Leaves alternate, petiolate or almost sessile; blade oblong-ovate, oblong, or lanceolate, base cuneate, margins sinuate-dentate, apex acute or mucronate. Inflorescences diffusely branched, paniculate, interrupted, linear spikes; flowers solitary or few in axils of short bracts. Flowers bisexual or pistillate; perianth segments 5, connate to above middle; stamens 5; stigmas 3. Fruiting structure: connate perianth segments enclosing utricle, at maturity forming horizontal, membranous, circular wing; pericarp membranous, free. Seeds horizontal, ovate-lenticular or globose-lenticular; seed coat black, smooth or indistinctly sculptured; embryo annular, perisperm copious. x = 9.

Traditionally, Cycloloma has been included in Chenopodieae (Chenopodiodeae). Recently it was placed in Camphorosmioideae (A. J. Scott 1978), mostly due to the presence of the broad wing formed by the encircling perianth segments. However, the development of the wing in Cycloloma seems to be very different from the mode of development of a similar wing (or other appendages) in Kochia, Bassia, and other genera of Camphorosmioideae. In my opinion, Cycloloma is more closely related to Chenopodium in the broad sense; the problem of its proper placement requires additional study.

Fls perfect or pistillate; cal persistent, 5- lobed to the middle, the segments usually keeled, incurved over the ovary; stamens 5; ovary flattened, discoid; styles (2)3; cal at maturity developing below its lobes a continuous, horizontal, erose or toothed, membranous wing; fr plano-convex, horizontal, black, puberulent, the pericarp free from the seed; embryo annular; densely branched annual tumbleweed with pale green lvs and slender, few-fld, terminal, interrupted spikes of minute green fls subtended by minute bracts; fr often turning purple. Monospecific.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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