Vernonia arkansana |
Asteraceae tribe vernonieae |
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Arkansas ironweed, great ironweed |
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Habit | Plants 8–12(–20) dm. | Annuals, biennials, perennials, or shrubs [trees or lianas] (sap rarely milky). | ||||||||||||||||||||
Stems | scabrellous to pilosulous, glabrescent. |
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Leaves | mostly cauline; blades lance-linear, 6–14(–20) cm × 7–15(–25) mm, l/w = 7–10(–18), abaxially scabrellous (hairs awl-shaped), resin-gland-dotted, adaxially scaberulous, glabrescent, resin-gland-dotted. |
usually cauline, sometimes basal or basal and cauline; alternate (rarely subopposite distally) [opposite]; usually petiolate, sometimes sessile (or petioles winged); margins usually ± dentate, sometimes entire [lobed or dissected]. |
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Peduncles | 2–5 cm. |
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Involucres | ± hemispheric, 11–15 × 11–15 mm. |
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Receptacles | flat to convex, usually epaleate (often foveolate, sometimes setose). |
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Florets | 50–100+. |
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Ray florets | 0 (corollas of peripheral florets enlarged, zygomorphic, ± raylike in Stokesia). |
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Disc florets | bisexual, fertile; corollas white, ochroleucous, or pink to cyanic [yellow]; anther bases ± sagittate [tailed], apical appendages ovate to lanceolate; styles abaxially hirsutulous (at least distally), branches lance-linear to ± lanceolate, adaxially continuously stigmatic from bases nearly to apices, apices acute, appendages essentially none. |
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Phyllaries | (50–)60–70+ in 5–6 series, scabrellous (and resin-gland-dotted), margins ciliolate, the outer lance-ovate, 3–8+ mm, inner lanceolate, 12–15 mm, tips subulate to filiform. |
usually persistent [readily falling], in 2–8+ series, distinct, unequal, herbaceous to chartaceous, margins and/or apices sometimes scarious. |
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Calyculi | 0. |
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Heads | in ± corymbiform arrays. |
homogamous (discoid, pseudo-radiant or -liguliflorous in Stokesia), usually in corymbiform, paniculiform, or scorpioid arrays, sometimes borne singly or in glomerules [aggregated in second-order heads]. |
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Cypselae | 3–5 mm; pappi fuscous to purplish, outer scales 25–30+, 0.5–1 mm, contrasting with 25–30+, 5–7 mm inner bristles. |
± monomorphic within heads, columnar to clavate, fusiform, or prismatic, sometimes compressed, not beaked, bodies smooth, nerved, or ribbed (glabrous or hirsutulous to strigillose, sometimes resin-gland-dotted as well); pappi usually persistent, usually in 2 series (outer series of shorter, stouter bristles or narrow scales, inner of longer, usually barbellate bristles), sometimes in 1 series (bristles or scales, scales often aristate). |
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2n | = 34. |
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Vernonia arkansana |
Asteraceae tribe vernonieae |
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Phenology | Flowering Aug–Oct. | |||||||||||||||||||||
Habitat | Leas, roadsides, stream banks, in sand or on limestone | |||||||||||||||||||||
Elevation | 200–300 m (700–1000 ft) | |||||||||||||||||||||
Distribution |
AR; KS; MO; OK
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Mostly tropics and warm-temperate regions of New World and Old World |
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Discussion | Vernonia arkansana was published in April, V. crinita in October 1838. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Genera 100–140, species ca. 1300 (6 genera, 25 species in the flora). Most members of Vernonieae are herbs, subshrubs, or shrubs (Vernonia arborea Buchanan-Hamilton of tropical Asia may form trees to 33 m). They are characterized by discoid heads of bisexual florets with purple to pink or white corollas, calcarate anthers, attenuate, abaxially hirsutulous style branches stigmatic ± uniformly (rather than in two lines or bands) nearly to their tips, and pollen grains with regular, polygonal, patterns of ± spiny to smooth ridges. Centers of species concentration for the tribe are found in Africa, Madagascar, South America, and Antilles. In the flora, most species are found in the eastern and southern states of the United States. The plants are often associated with open, prairie or savanna-like areas. Treating clades recognized by J. L. Panero and V. A. Funk (2002) as corresponding to tribes, Vernonieae is sister to Liabeae (none in the flora) and is included with Arctotideae (introduced), Cichorieae, and Gundelieae (none in the flora) within Cichorioideae. Historically, 80% or so of the species in the tribe were included in Vernonia. H. Robinson (1999) has argued for resurrections and recircumscriptions of some old genera and recognition of some “new” genera, resulting in a Vernonia of ca. 20 species. Stokesia laevis and some Vernonia species are grown as ornamentals. Some Vernonia species have been used medicinally in folk remedies and some may be locally troublesome as weeds (e.g., V. baldwinii). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 19, p. 208. | FNA vol. 19, p. 200. | ||||||||||||||||||||
Parent taxa | Asteraceae > tribe Vernonieae > Vernonia | Asteraceae | ||||||||||||||||||||
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Synonyms | V. crinita | |||||||||||||||||||||
Name authority | de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 7: 264. (1838) | Cassini: J. Phys. Chim. Hist. Nat. Arts 88: 203. (1819) | ||||||||||||||||||||
Web links |