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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California
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ASTERACEAE

SUNFLOWER FAMILY

David J. Keil, Family Editor and author, except as specified

Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1–many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1–many per head
Flowers bisexual, unisexual, or sterile, ± small, of several types; calyx 0 or modified into pappus of bristles, scales, or awns, which is generally persistent in fruit; corolla radial or bilateral (rarely 0), lobes generally (0)4–5; stamens 4–5, anthers generally fused into cylinder around style, often appendaged at tips, bases, or both, filaments generally free, generally attached to corolla near throat; pistil 1, ovary inferior, 1-chambered, 1-seeded, style 1, branches 2, generally hair-tufted at tip, stigmas 2, generally on inside of style branches
Fruit: achene, cylindric to ovoid, generally deciduous with pappus attached
Genera in family: ± 1300 genera, 21,000 species (largest family of dicots): worldwide. Largest family in CA. Also see tribal key to CA genera: Strother 1997 Madroño 44(1):1–28. See glossary p. 25 for illustrations of general family characteristics.

AMBROSIA

RAGWEED, BUR-SAGE

Willard W. Payne

Annual to shrub, monoecious
Leaves often opposite below, generally alternate above, generally petioled, hairy, glandular
Inflorescence: staminate heads generally many in ± spikes or racemes, phyllaries fused into shallow cup; pistillate heads generally clustered below staminate, generally spiny, bur-like; involucre ± 0; receptacle chaffy; chaff scales spirally arrayed, fused below, tips generally becoming spiny; each pistillate flower in separate chamber
Staminate flowers ± many; corolla yellow or translucent; anthers free; style unbranched
Pistillate flowers 1–5; corolla 0; style branches long
Fruit enclosed in bur; pappus 0
Etymology: (Greek: early name for aromatic plants; the mythic food of the gods)
[Payne 1976 Plant Syst Evol 125:169–178] Closely related to (indistinct from) Hymenoclea [Miao et al. 1995 Amer J Bot 82:924–932; Baldwin et al. 1996 Madroño 43:15–27] Wind-blown pollen often highly allergenic.

Native

A. eriocentra (A. Gray) Payne

WOOLLY BUR-SAGE

Shrub 3–18 dm, ± spheric
Stems gray-brown, ± woolly, becoming glabrous
Leaves: petioles winged; blades 1–9 cm, ± lanceolate, coarsely toothed or pinnately lobed, ± rolled under, ± green above,
Inflorescence: staminate heads few, 5–7 mm diam, involucre lobes 5–8; pistillate heads generally 1-flowered
Fruit: bur 8–11 mm, greenish brown, densely long-soft-hairy; spines 12–20, generally near middle, straight, flat, stout, sharp, tips ± hair-tufted
Chromosomes: 2n=36
Ecology: Dry washes and slopes
Elevation: 800–1700 m.
Bioregional distribution: eastern Mojave Desert, Desert Mountains
Distribution outside California: to sw Utah, nw Arizona
Flowering time: Mar–May

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bioregional map for AMBROSIA%20eriocentra being generated
 
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Retrieve Jepson Interchange Index to Plant Names entry for Ambrosia eriocentra
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