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



Annual, perennial herb, glabrous or hairy, sometimes glandular
Stem generally scapose (made up of inflorescence axes)
Leaves basal (rarely some cauline); stipule 0; blade generally ± oblanceolate
Inflorescence open or of few heads, sometimes 1-sided; bracts generally opposite, leaf-like to scale-like; involucres 1–several per axil, sessile, tube cylindric to bell-shaped, generally ± cross-ridged or net-veined, bracts (and ribs) 3–6, awns straight or hooked; flowers 1–2 per involucre
Flower: perianth white to red or yellow, lobes 6, entire to fringed or toothed; stamens 3–9
Fruit 1.5–4.5 mm, generally ± brown, glabrous
Species in genus: 50 species: temp w North America, sw South America
Etymology: (Greek: divided flower, from perianth)
Reference: [Reveal & Hardham 1989 Phytologia 66(2):98–198]


C. rigida (Torr.) Torr. & A. Gray


Stem erect, densely branched, 2–15 cm, greenish, hairy
Leaf long-petioled; blade generally 5–10 mm, oblanceolate to elliptic, hairy; rosette withering early
Inflorescence: main bracts like leaves but larger (blade generally 10–35 mm) and wider, later bracts many, spine-like, < 30 mm; involucral tube 2–3 mm, funnel-shaped, bracts 3, 2–10 mm (1 much the longest), lanceolate, awns straight,
Flower: perianth < 2 mm, included, yellow, densely hairy; stamens 9, attached near top of perianth tube
Chromosomes: n=19,20
Ecology: Common. Desert scrub
Elevation: < 2000 m.
Bioregional distribution: East of Sierra Nevada, Desert
Distribution outside California: to sw Utah, w Arizona, nw Mexico
Flowering time: Mar–May
Dead spiny skeletons persist.

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