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.

EMEX

Annual, monoecious, glabrous
Stem decumbent to erect, 3–8 dm
Leaves cauline, alternate, petioled; stipules fused, sheathing stem above nodes; blade base ± cordate
Staminate inflorescence: panicle, axillary
Pistillate inflorescence: cluster, axillary, small
Staminate flower: perianth lobes 5; stamens 4–6
Pistillate flower: perianth lobes 6
Fruit enclosed in woody perianth tube that has 3 major spines
Species in genus: 2 species: Medit, s Africa, Australia
Etymology: (Latin: from Rumex )

Introduced

E. spinosa (L.) Campdera

DEVIL'S THORN

Fruit: perianth ± urn-shaped, sculpture fine, regular, netted or ladder-like, inner lobes ± elliptic
Chromosomes: 2n=20
Ecology: Uncommon. Disturbed places
Elevation: < 500 m.
Bioregional distribution: South Coast, expected elsewhere
Distribution outside California: native to Mediterranean
Weedy.