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ASTERACEAE (Compositae) SUNFLOWER FAMILY

David J. Keil, except as noted

Annual to tree. Leaf: basal and/or cauline, alternate, opposite, rarely whorled, simple to 2+ × compound. Inflorescence: 1° inflorescence a head, resembling a flower, of several types (see below), 1–many in generally ± cyme-like cluster; each head generally with ± calyx-like involucre of 1–many series of phyllaries (involucral bracts); receptacle of head flat to conic or columnar, paleate (bearing paleae = receptacle bracts) or epaleate; flowers 1–many per head. Flower: bisexual, unisexual, or sterile, ± small, of several types (see below); calyx 0 or modified into ± persistent pappus of bristles, scales, and/or awns; corolla radial or bilateral (0), lobes generally (0)3–5; stamens 4–5, filaments generally free, generally fused to corolla at tube/throat junction, anthers generally fused into cylinder around style, anther base generally rounded or cordate (deeply sagittate or with tail-like appendages), tip (= flattened appendage) generally projecting beyond pollen sac; pistil 1, 2-carpeled, ovary inferior, 1-chambered, 1-seeded, placenta basal, style 1, tip generally ± 2-branched (except in some staminate disk flowers), branch tips truncate or generally bearing ± brush-like appendages; stigmas 2, generally on adaxial faces of style branches. Fruit: achene (also called a cypsela) (drupe in Chrysanthemoides), cylindric to ovoid, sometimes compressed, generally deciduous with pappus attached.
± 1500 genera, 23000 species: worldwide, many habitats. Flower and head types differ in form and sexual condition. A disk flower has a generally radial corolla, with a cylindric tube, expanded throat, and generally 5 lobes. Disk flowers are generally bisexual and fertile but occasionally staminate with reduced ovaries. Discoid heads comprise only disk flowers. A radiant head is a variant of a discoid head, with peripheral disk flower corollas expanded, often bilateral. A ray flower corolla is bilateral, generally with a slender tube and flattened petal-like ray (single lip composed of generally 3 lobes). Ray flowers are generally pistillate or sterile (occasionally lacking styles). Radiate heads have peripheral ray flowers and central disk flowers. Disciform heads superficially resemble discoid heads, with pistillate or sterile flowers that lack rays, together with or separate from disk flowers. A ligulate flower is bisexual, with a bilateral, generally ephemeral corolla and 5-lobed ligule. Liguliflorous heads comprise only ligulate flowers. See glossary p. 31 for illustrations of family characteristics. Echinops sphaerocephalus L., Gaillardia aristata Pursh, Gaillardia pulchella Foug., Hymenothrix loomisii S.F. Blake, Tagetes erecta L., Thelesperma megapotamicum (Spreng.) Kuntze are waifs. Melampodium perfoliatum Kunth, historic urban waif. Ageratum conyzoides L., Guizotia abyssinica (L. f.) Cass., Santolina chamaecyparisus L., orth. var. are rare or uncommon escapes from cultivation. Dyssodia papposa, Ismelia carinata (Schousb.) Sch. Bip. [Chrysanthemum carinatum Schousb.], Mantisalca salmantica (L.) Briq. & Cavill. are historical or extirpated waifs in California. Inula helenium L. not documented in California. Taxa of Aster in TJM (1993) treated here in Almutaster, Eucephalus, Eurybia, Ionactis, Oreostemma, Sericocarpus, Symphyotrichum; Chamomilla in Matricaria; Cnicus in Centaurea; Conyza in Erigeron and Laennecia; Dugaldia in Hymenoxys; Erechtites in Senecio; Hymenoclea in Ambrosia; Lembertia in Monolopia; Osteospermum ecklonis in Dimorphotheca; Picris echioides in Helminthotheca; Prionopsis in Grindelia; Raillardiopsis in Anisocarpus and Carlquistia; Schkuhria multiflora in Bahia; Trimorpha in Erigeron; Venidium in Arctotis; Whitneya in Arnica. Taxa of Arida in TJM2 treated here in Leucosyris. —Scientific Editors: David J. Keil, Bruce G. Baldwin.
Unabridged note: Largest family of vascular plants in California and of eudicots globally.

Key to Asteraceae

BIDENS
Annual, perennial herb [shrub]. Stem: prostrate to erect. Leaf: simple or pinnate, generally opposite, sessile or petioled. Inflorescence: heads radiate or discoid, occasionally disciform, generally few in California; involucre cylindric to bell-shaped; phyllaries in 2 dissimilar series, outer generally ± leaf-like in texture, inner thinner, with transparent or scarious margins; receptacle paleate; paleae narrow, flat. Ray flower: 0 or few; ray yellow or white. Disk flower: generally many; corolla yellow, radial (or outermost white, bilateral). Fruit: narrowly club-shaped, thick or compressed front-to-back; pappus 0 or awns 1–several, generally barbed.
± 230 species: worldwide. (Latin: 2 teeth) [Strother & Weedon 2006 FNANM 21:205–218]

Key to Bidens

B. cernua L. NODDING BUR-MARIGOLD
NATIVE
Annual. Stem: 1–9 dm, erect, glabrous to short-rough-hairy. Leaf: simple, sessile; bases fused around stem; blades 4–20 cm, lance-linear to lanceolate, acuminate, serrate, glabrous. Inflorescence: heads radiate or discoid, erect in flower, nodding in fruit; peduncle 1–7 cm; involucre 1–2 cm diam, hemispheric; outer phyllaries 5–8, 1–3 cm, lance-linear, spreading; inner phyllaries 8–10 mm, lance-ovate; paleae 6–8 mm, tips yellow. Ray flower: 0 or 6–8; ray 8–15 mm, yellow. Disk flower: corolla 3–4 mm, yellow. Fruit: 5–7 mm, narrowly wedge-shaped, 4-angled, compressed front-to-back; angles thick, barbed; pappus awns generally 4, 2–3 mm.
2n=24, 48. Freshwater wetlands; < 2000 m. Klamath Ranges, North Coast Ranges, Cascade Range, n Sierra Nevada, n Central Coast, Great Basin Floristic Province; widespread northern hemisphere. Much like Bidens laevis. Jul–Oct [Online Interchange]

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Nov 1 2014
Citation for this treatment: [Author of taxon treatment] 2013. Bidens, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=1682, accessed on Nov 1 2014

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click for enlargement Bidens cernua
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© 2006 Louis-M. Landry

Geographic subdivisions indicated for the distribution of Bidens cernua Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.