| TREATMENT FROM THE JEPSON MANUAL (1993) |
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©Copyright 1993 by the Regents of the University of California
For up-to-date information about California vascular plants, visit the Jepson eFlora. |
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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.
Subshrub to small tree, monoecious
Stems slender
Leaves alternate, entire or narrowly lobed, white-hairy above; margins curled upward
Inflorescence: staminate heads many, in spike- or panicle-like clusters; phyllaries 4–8, fused into shallow cup, greenish; receptacle chaffy; pistillate heads ± spheric, beaked, in fruit winged, 1-flowered, ± bur-like, phyllaries 0–few, chaff scales ± fused, free tips winged, papery
Staminate flowers 4–18; corolla translucent; filaments and anthers free; style unbranched
Pistillate flower: corolla 0; style branches long; pappus 0
Fruit enclosed in bur, dispersed by wind or water
Species in genus: 2–4 species: sw US, n Mex
Etymology: (Greek: membrane-enclosed, from bur)
Reference: [Peterson & Payne 1974 Brittonia 26:397]
Like Ambrosia, Xanthium.
| Native |
Shrub or small tree 1–4 m, much-branched above
Stems straw-colored to dark brown; old bark gray-brown
Inflorescence: fruit heads 2–4 mm, fusiform; wings 7–12, 1.5–2 mm, < 1.5 mm wide, oblanceolate, in 1 central whorl
Ecology: Washes, dry riverbeds
Elevation: < 500 m.
Bioregional distribution: Southwestern California, East of Sierra Nevada, Sonoran Desert
Distribution outside California: to w Nevada, Texas, n Mexico
Flowering time: Aug–Nov
Recent taxonomic note: Ambrosia monogyra (A. Gray) Strother & B.G. Baldwin