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Project Name Data (Last Modified On 6/17/2013)
 

Flora Data (Last Modified On 6/17/2013)
Genus Bidens L.
PlaceOfPublication Gen. P1., ed. 5. 362. 1754.
Note TYPE: B. tripartita L.
Synonym Pluridens Neck., Elem. Bot. 1: 86. 1790, nom. mut. Bidens L. Edwardsia Neck., Elem. Bot. 1: 1790, nom. mut. Bidens L. Kerneria Moench, Meth. 595. 1794. TYPE: K. trigona Moench = Bidens pilosa L. Ceratocephalus Cass., Dict. Sci. Nat. 7: 432. 1817. TYPE: Bidens pilosa L. Delucia DC., Prodr. 5: 633. 1836. TYPE: D. ostruthioides DC. Diodonta Nutt., Trans. Amer. Phil Soc., n.s. 7: 360. 1841. LECTOTYPE: D. leptophylla Nutt. = Bidens mitis (Michx.) Sherff. Diadonta Walp., Repert. Bot. Syst. 2: 614. 1843, orth. mut. Diodonta Nutt. MAcocotli Hernandez, Altam. Mat. Med. Mex. 2: 154. 1898, cf. Sherff, N. Amer. Flora, ser. 2, 2: 113. 1955.
Description Herbs, perennial or annual, erect, scandent or procumbent, rarely shrubby or paludal; stems mostly pubescent and drying striate or sulcate, at least when young. Leaves opposite, simple or compound, serrate, lobed or dissected, rarely entire, mostly petiolate. Inflorescences of solitary, sometimes aggregated terminal heads; peduncles slender, narrowing upwards, striate, subtended by paired, foliaceous bracts and often by one or more alternately disposed foliaceous or scalelike bracteoles along their length. Heads mostly radiate, sometimes showy; involucre of an outer series of distinct, herbaceous, acute or rarely foliaceous bracts and an inner series of broader, membranous, sometimes basally united bracts, the margins often hyaline; receptacle flat or convex; paleas resembling the inner involucral bracts but narrower, slightly curved around the ovary; ray florets few-many in 1 series or wanting, the corolla with a broad, apically denticulate limb, drying with longitudinal nerves, the tube short, the ovary sometimes fertile; disc florets numerous, the corolla tubular, the 5-lobes yellowish, glabrous or puberulent on the ventral surface, the anthers often black, basally obtuse or subauriculate, the appendages large, the style branches flattened, apically pilose with a short, narrow appendage, the ovary mostly fertile. Achenes black or brown, narrowly fusiform or linear, sulcate, often apically ascending-strigose, mostly surmounted by 1-6 retrorsely strigose awns held at various angles, those of the marginal disc florets sometimes different from those of the central disc florets, those of the rays sometimes flattened, broad.
Habit Herbs
Distribution Bidens is a genus of about 75 species mainly of Mexico but ranging into North and South America.
Note Several species are widely naturalized as weeds. It is closely related to Coreopsis and Cosmos.
Reference Sherff, E. E. 1937. The genus Bidens. Field Mus. Nat. Hist., Bot. Ser. 16: 1-709.
Key a. Plant erect, annual; ray florets not showy, yellow or white, less than 12 mm long, or wanting. b. Leaves 3(-5)-foliolate, the leaflets serrate; achenes straight. c. Achenes less than 12 mm long, the awns erect ...... 3. B. pilosa cc. Achenes more than 12 mm long, the awns divaricate, sometimes reflexed ...... 5. B. riparia var. refracta bb. Leaves 2-3-pinnately divided, the leaflets deeply toothed or lobed; achenes curved ...... 1. B. bipinnata var. cynapiifolia aa. Plants procumbent, ascending or scandent, not erect, perennial; ray florets showy, yellow or orange, more than 12 mm long. d. Plants scandent, the shoots more than 45 cm long; the solid portions of the leaf blade more than 10 mm wide, the margins serrate ...... 4. B. reptans dd. Plants procumbent, rooting at the lower nodes, the ascending shoots less than 30 cm long; the solid portions of the leaf blade less than 10 mm wide, the margins deeply toothed or lobed. e. Ray florets fertile; style branches conspicuous in living material ...... 2. B. ostruthioides var. costaricensis ee. Ray florets sterile; style branches mostly wanting ...... 6. B. triplinervia
 
 
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