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©Copyright 1993 by the Regents of the University of California
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POLYGONACEAE

BUCKWHEAT FAMILY

James C. Hickman

Annual to trees, some dioecious
Stem: nodes often swollen
Leaves simple, basal or cauline, alternate, opposite, or whorled, generally entire; stipules 0 or obvious and fused into a generally scarious sheath around stem
Inflorescence: small cluster, axillary or arrayed in cymes or panicles; involucres sometimes subtending 1–many flowers
Flower generally bisexual, small, ± radial; perianth generally 5–6-lobed, base ± tapered, often jointed to pedicel; stamens 2–9, often in 2 whorls; ovary superior, styles generally 3, generally fused at base
Fruit: achene, generally enclosed by persistent perianth, generally 3-angled, ovoid, and glabrous
Genera in family: 50 genera, 1100 species: worldwide, especially n temp; some cultivated for food (Fagopyrum ; Rheum , rhubarb; Rumex , sorrel) or ornamental (Antigonon , coral-vine; Muehlenbeckia ; Polygonum )
Reference: [Ronse Decraene & Akeroyd 1988 Bot J Linn Soc 98:321–371; Reveal et al. 1989 Phytologia 66(2–4):83–414]
Treatments of the 15 eriogonoid genera are based on the monographic work of James L. Reveal, who is gratefully acknowledged.

OXYTHECA

Annual, glandular, glaucous
Leaves basal; stipule 0; petiole indistinct; blade linear to obovate, hairy
Inflorescence open; bracts generally 3 per node, generally linear-lanceolate, generally fused at base, awned; involucre 1 per node, generally stalked, narrowly funnel-shaped to bell-shaped, teeth 3–36, awned; flowers 2–20 per involucre
Flower: perianth white to rose or pale yellow, hairy, lobes 6; stamens 9
Fruit golden-brown to dark brown. w North America., s South America
Etymology: (Latin: sharp box, from involucre)
Reference: [Ertter 1980 Brittonia 32:70–102]

Native

O. dendroidea Nutt. subsp. dendroidea

Plant 5–40 cm
Leaf 1–4.5 cm, generally narrowly oblanceolate, hairy, sparsely glandular
Inflorescence sparsely glandular; bract awns 0–0.5 mm; branches sometimes recurved; involucre narrowly funnel-shaped, glabrous, involucral bracts 4, 1–2 mm, < half fused, awns 0.5–3 mm; flowers 2–6 per involucre
Flower: perianth 1–2 mm, white to pink, strigose, lobes entire
Fruit 1.5–2 mm
Chromosomes: n=20
Ecology: Dry sandy places in scrub or pine forest:
Elevation: 1200–2200 m.
Bioregional distribution: Great Basin Floristic Province
Distribution outside California: to Washington, Wyoming, Nevada
Flowering time: Jun–Sep

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