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Published In: Species Plantarum 2: 831. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted

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66. Bidens L. (beggar-ticks)

Plants annual or perennial herbs (shrubs elsewhere). Stems erect to loosely ascending (except in submerged aquatics), unbranched or more commonly few- to numerous-branched, with several fine to coarse longitudinal lines or ridges, sometimes relatively strongly 4- or 5-angled, glabrous or sparsely to moderately pubescent. Leaves opposite or less commonly in whorls of 3 and sometimes also basal, variously sessile to long-petiolate, the bases slightly expanded and wrapping around the stem. Leaf blades simple or 1–3 times pinnately lobed, dissected, or compound (repeatedly dichotomously dissected in submerged leaves of B. beckii), variously shaped, the margins otherwise usually toothed, glabrous or variously hairy, not glandular. Inflorescences of solitary terminal heads or appearing as loose, open clusters or small panicles, occasionally some of the heads appearing axillary, the heads with short to long, bractless stalks or rarely the stalk with 1 or 2 inconspicuous, minute bracts. Heads radiate or discoid. Involucre broadly to narrowly cup-shaped to slightly bell-shaped, the bracts in 2(3) dissimilar overlapping series. Involucral bracts free at the base, those of the outer series 2–25, mostly as long as or longer than the others, variously shaped, green, glabrous or sparsely to moderately hairy, not glandular, usually inconspicuously 1- or 3-nerved; those of the inner series 5–8(–12), variously shaped, yellowish brown to yellowish green, more or less scalelike with narrow to broad, lighter, thinner margins, glabrous (inconspicuously hairy in B. alba), not glandular, with several to numerous conspicuous nerves or longitudinal lines. Receptacle flat or slightly convex, not elongating as the fruits mature, with chaffy bracts subtending the disc florets, these linear to narrowly oblong or narrowly lanceolate, relatively flat to somewhat concave, sometimes slightly wrapped around the florets toward the base. Ray florets absent or 1–8(–12), when present sterile (lacking stamens and style at flowering and with an ovary that is shorter and thinner than those of the disc florets, not developing into a fruit; pistillate elsewhere), the corolla inconspicuous or showy, 2–30 mm long, relatively broad, yellow or white, not persistent at fruiting. Disc florets 10–100(–150), perfect, the corolla usually 5-lobed (sometimes 4-lobed in B. tripartita), yellow to orangish yellow, not thickened at the base, not persistent at fruiting. Style branches with the sterile tip slightly to moderately elongate and tapered to a sharply pointed tip. Pappus of the disc florets of (1)2–4(–8) short or long awn(s) (these smooth or with sparse, upward- or downward-angled barbs), rarely absent, when present usually persistent at fruiting. Fruits 3–18 mm long, sometimes dissimilar in the same head (the outer ones grading into the inner ones) narrowly oblong to linear in outline, strongly flattened or 4-angled, not appearing curved or curled, more or less truncate at the tip, not beaked, the angles lacking wings or less commonly with slender wings, the surfaces often angled or with 1 or more longitudinal grooves, glabrous or variously hairy, tan to dark brown or nearly black, sometimes mottled, the wings (if present) usually pale, sometimes slightly shiny. More than 200 species, nearly worldwide.

As noted in the treatment of the genus Coreopsis, that genus is difficult to separate from Bidens, and further research undoubtedly will result in the revision of generic circumscriptions in the subtribe Coreopsidinae. In addition, some of the species of Bidens are difficult to distinguish from one another. Barkley (1986) advised studying several specimens when attempting to identify Bidens species.


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1.1. Plants submerged aquatics with 2 dissimilar kinds of leaves, the submerged portion with the leaves repeatedly dichotomously dissected into narrowly linear (threadlike) segments, grading abruptly into the emergent leaves, which are unlobed; fruits more or less circular in cross-section; pappus 13–30 mm long ... 3. B. BECKII

Bidens beckii
2.1. Plants terrestrial or less commonly emergent aquatics (occasionally epiphytic), the leaves all unlobed or more or less similar in lobing or dissection; fruits flattened or 4-angled in cross-section; pappus absent or more commonly 2–8 mm long

3.2. Ray florets present, the corolla white ... 1. B. ALBA

Bidens alba
4.2. Ray florets absent or, if present, then the corolla yellow

5.3. Leaf blades all unlobed or, if lobed or divided, then at most with 3–5 divisions, none of the divisions of the lobed leaves stalked at the base

6.4. Outer series of involucral bracts loosely ascending to spreading; heads not nodding at fruiting; heads discoid or less commonly radiate, when ray florets are present then 1–5, the corollas 3–8 mm long ... 10. B. TRIPARTITA

Bidens tripartita
7.4. Outer series of involucral bracts spreading or more commonly reflexed; heads usually nodding at fruiting; heads radiate or rarely discoid, when ray florets are present then 6–8, the corollas (2–)10–30 mm long

8.5. Chaffy bracts straw-colored to yellowish-tinged at the tip; ray florets (when present) with the corolla (2–)10–15 mm long; angles of the fruit pale and somewhat thickened or sometimes narrowly winged ... 5. B. CERNUA

Bidens cernua
9.5. Chaffy bracts reddish brown to orangish brown at the tip; ray florets (when present) with the corolla (10–)15–30 mm long; angles of the fruit not paler than the body, not thickened or winged ... 8. B. LAEVIS

Bidens laevis
10.3. At least some of the leaves with the blades 1–3 times pinnately or ternately lobed, divided, or compound, the divisions or leaflets more than 5 or, if only 3, then at least the central segment or leaflet usually tapered to a stalked base

11.6. Heads radiate, the ray florets 5–8, showy, the corollas 10–25 mm long

12.7. Fruits mostly 1.5–2.5 times as long as wide, wedge-shaped to obovate in outline; disc florets with the corolla 2.0–3.5 mm long ... 2. B. ARISTOSA

Bidens aristosa
13.7. Fruits mostly 2.5–5.0 times as long as wide, narrowly wedge-shaped to oblong-oblanceolate or nearly linear in outline; disc florets with the corolla 3–5 mm long ... 9. B. TRICHOSPERMA

Bidens trichosperma
14.6. Heads discoid or less commonly radiate, when ray florets are present then 1–5, inconspicuous, the corollas 2–4 mm long

15.8. All except sometimes the uppermost leaves with the blades 2 or 3 times pinnately lobed, divided, and/or compound into 7 to numerous ultimate lobes or segments; fruits linear in outline, strongly 4-angled (more or less square in cross-section) ... 4. B. BIPINNATA

Bidens bipinnata
16.8. All of the leaves with the blades 1 time ternately or pinnately divided or compound into 3 or 5 divisions or leaflets; fruits wedge-shaped to narrowly oblong-obovate in outline, flattened, often slightly 3- or 4-angled (1 or both faces sometimes with a broad, low longitudinal angle or ridge)

17.9. Involucral bracts of the outer series 3–5, the margins glabrous; disc florets 10–20, the corolla 1.5–2.0 mm long; pappus rarely absent, usually of 2 awns 0.5–2.0 mm long; fruits 3–6 mm long ... 6. B. DISCOIDEA

Bidens discoidea
18.9. Involucral bracts of the outer series 5–21, the margins with spreading hairs, at least toward the base; disc florets 20–100(–150), the corolla 2.5–4.0 mm long; pappus of 2 awns 2–7 mm long; fruits 5–12 mm long

19.10. Involucral bracts of the outer series mostly 5–8 ... 7. B. FRONDOSA

Bidens frondosa
20.10. Involucral bracts of the outer series mostly 10–21 ... 11. B. VULGATA
Bidens vulgata
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