[*] Achenes flat, not tapering at the summit; outer involucre foliaceous; annuals.
[+] Heads erect, nearly rayless; leaves mostly petiolate.
1. B. frondòsa, L. (Common Beggar-ticks. Stick-tight.) Smooth or rather hairy, tall (2–6° high), branching, leaves 3–5-divided; leaflets mostly stalked, lanceolate, pointed, coarsely toothed; outer involucre much longer than the head, ciliate below; achenes wedge-obovate, 2-awned, ciliate (the bristles ascending except near the summit).—Moist waste places; a coarse troublesome weed, the achenes, as in the other species, adhering to clothing, etc., by their retrorsely barbed awns. Hybrids occur with Coreopsis aristosa and other species. July–Oct.
2. B. connàta, Muhl. (Swamp Beggar-ticks.) Smooth (1–2° high); leaves lanceolate or oblong-lanceolate, pointed, sharply serrate, tapering into margined slightly united petioles; the lower often 3-divided, their lateral divisions united at the base and decurrent on the petiole; outer scales longer than the head, few, mostly obtuse; rays none; achenes narrowly wedge-form, 3- (2–4-) awned, the margins minutely retrorsely ciliate.—E. New Eng. to Minn., and southward.—Var. comòsa, Gray, is stouter, the leaves commonly all simple, upper ones nearly sessile, the heads larger and with very leafy involucre. Ill., Ky., and westward. Aug.–Oct.—Var. pinnàta, Watson; leaves nearly all pinnately divided, the 5–7 narrow divisions sparingly incised; achenes 4-awned. Hennepin Co., Minn. (F. L. Conillard).
[+][+] Heads somewhat nodding, commonly radiate; leaves sessile, undivided.
3. B. cérnua, L. (Smaller Bur-Marigold.) Nearly smooth (5´–3° high), leaves lanceolate, unequally serrate, scarcely connate; heads nodding, with or without (light yellow) rays; outer involucre longer than the head; achenes wedge-obovate, 4-awned, the margins downwardly barbed.—Wet places, N. Eng. to Va., Mo., Minn., and northward. July–Sept.—Rays, if any, smaller than in n. 4, and the outer involucre more leaf-like. (Eu.)
4. B. chrysanthemoìdes, Michx. (Larger Bur-Marigold.) Smooth, erect, or reclining at the base (6´–2° high); leaves lanceolate, tapering at both ends, more or less connate, regularly serrate; outer involucre mostly shorter than the showy golden-yellow (1´ long) rays; achenes wedge-shaped, with almost prickly downwardly barbed margins; awns 2, 3, or 4.—Swamps; common. Aug.–Oct.
[*][*] Achenes linear, 4-sided, the inner longer and tapering upward.
5. B. bipinnàta, L. (Spanish Needles.) Smooth annual, branched; leaves 1–3-pinnately parted, petioled; leaflets ovate-lanceolate, mostly wedge-shaped at the base; heads small, on slender peduncles; outer involucre of linear scales equalling the short pale yellow rays, achenes 4-grooved and angled, nearly smooth, 3–4-awned.—Damp soil, R. I. to N. Y., Ill., and southward.
[*][*][*] Achenes terete, truncate at both ends, with 3–6 very long awns smooth below.