9. Bidens trichosperma (Michx.) Britton
B. coronata (L.) Britton (1913), not B. coronata
Fisch. ex Colla (1834)
Pl. 273 e, f;
Plants annual or
biennial, terrestrial, sometimes with taproots. Stems
15–80(–150) cm, erect or ascending, glabrous or nearly so.
Leaves all more or less similar, short-petiolate, opposite, the blade
2–12 cm long, mostly ovate or triangular-ovate in outline, 1 or 2 times
deeply pinnately divided or compound into 3–7(–9) segments or
leaflets, these linear to more commonly lanceolate to oblanceolate, angled or
tapered at the base, the middle one frequently with a stalklike base, tapered
to a sharply pointed tip, the margins usually sharply and finely to coarsely
toothed, rarely entire or nearly so, the surfaces glabrous or sparsely hairy.
Inflorescences of solitary terminal heads or appearing in loose, open clusters
or small panicles, the heads radiate, not nodding at fruiting. Involucre with
the outer series of (6–)8(–11) bracts 4–8 mm long,
ascending to spreading, somewhat leaflike, linear to narrowly oblanceolate, the
margins entire but sometimes with minute, ascending hairs, the surfaces
glabrous; the inner series of 6–8 bracts 4–8 mm long,
oblong-elliptic, glabrous. Chaffy bracts narrowly oblong-lanceolate, usually
with broad, yellowish margins and tip, occasionally purplish-tinged at the tip.
Ray florets (6–)8(–9), the corolla showy, 10–25 mm
long, yellow. Disc florets 40–80(–120), the corollas
3–5 mm long, yellow. Pappus of 2 awns 1–4 mm long (rarely
shorter and scalelike), these with upward barbs, erect to somewhat spreading at
fruiting. Fruits 4–8 mm long, narrowly wedge-shaped to
oblong-oblanceolate or nearly linear (mostly 2.5–5.0 times as long as
wide), more or less flattened and somewhat 4-angled in cross-section, the
angles roughened with short, stiff, ascending, pustular-based hairs, the faces
sometimes with 1 or few faint longitudinal line(s), dark brown to black,
sparsely to moderately pubescent with short, fine, mostly appressed hairs. 2n=24.
known thus far only from the city of St. Louis (eastern [mostly northeastern] U.S. west to Minnesota, Nebraska, and Mississippi). Railroads.
This species was
first reported for Missouri by Mühlenbach (1979).