Bidens heterodoxa
Rhodora 17: 23. 1915.
Annuals, (5–) 25–35 (–55+) cm. Leaves: petioles (narrowly, if at all, winged) 5–20 (–35+) mm; blades lanceolate to lance-linear, (20–) 30–50 (–80+) × (3–) 6–20 (–30+) mm, sometimes laciniately 1-pinnatisect with 2–4+ lobes near bases, bases cuneate, margins incised to serrate, seldom ciliate, apices acute to attenuate, faces glabrous. Heads borne singly or in 2s or 3s. Peduncles 10–35 (–55) mm. Calyculi of (2–) 3–5 (–7) ± erect, oblanceolate or spatulate to linear, ± foliaceous bractlets or bracts (6–) 10–25 (–40+) mm, margins rarely ciliate, abaxial faces usually glabrous, sometimes sparsely hispidulous. Involucres usually obconic to broadly campanulate, rarely hemispheric, (4–) 6–7 × (4–) 5–7 mm. Phyllaries (4–) 5–8,oblong to lanceovate, (4–) 5–8+ mm. Ray-florets usually 0, sometimes 1–3+; laminae orange yellowish, 2–5 (–10) mm. Disc-florets (7–) 20–70+; corollas yellowish, 2.5–3.5 mm. Cypselae: outer redbrown, ± flattened, sometimes 3–4-angled, broadly cuneate, 4–5 (–6) mm, inner blackish, narrowly cuneate, (5–) 6–7 (–8+) mm, margins glabrous or sparsely antrorsely strigillose,apices ± truncate to convex, faces ± 1-nerved, glabrous or sparsely setulose, usually smooth, sometimes ± tuberculate; pappi 0, or of 2 (–4) spreading to divergent, antrorsely or retrorsely barbed awns (0.1–) 1–3.5+ mm. 2n = 48.
Phenology: Flowering Aug–Oct.
Habitat: Borders of estuaries, lakes, marshes, streams
Elevation: 0–10 m
Distribution
N.B., P.E.I., Que., Conn.
Discussion
Bidens heterodoxa may be better treated as part of B. tripartita.
Selected References
None.