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Jepson Interchange (more information)
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  • Up-to-date information about California vascular plants is available from the Jepson eFlora.

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.

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