6. Bidens discoidea (Torr. & A. Gray) Britton (few-bracted bur marigold)

Pl. 274 g, h; Map 1154

Plants annual, terrestrial or epiphytic, usually with taproots. Stems 15–80(–150) cm, erect or ascending, glabrous. Leaves all more or less similar, short- to long-petiolate, opposite, the blade 3–15 cm long, broadly ovate-triangular in outline, all except rarely those of the uppermost leaves 1 time ternately (pinnately) compound with 3 discrete leaflets, these lanceolate to obovate, mostly angled at the base, each with a well-developed stalk, tapered to a sharply pointed tip, the margins usually sharply and relatively coarsely toothed, sometimes minutely hairy, the surfaces glabrous or the undersurface sparsely to moderately pubescent with minute, fine hairs. Inflorescences of solitary terminal heads or appearing in loose, open clusters or small panicles, the heads discoid, sometimes nodding or spreading at fruiting. Involucre with the outer series of 3–5 bracts 8–25 mm long, ascending to spreading, leaflike, linear to narrowly oblong-oblanceolate or narrowly oblanceolate, the margins entire and glabrous (rarely with a few hairs toward the base), the outer surface glabrous or sparsely and minutely hairy, especially toward the base; the inner series of 5–7 bracts 4–7 mm long, oblong to narrowly lanceolate, glabrous. Chaffy bracts narrowly oblong to oblong, usually with broad, yellowish margins but purplish-tinged at the tip. Ray florets absent. Disc florets 10–20, the corollas 1.5–2.0 mm long, yellow. Pappus rarely absent, usually of 2 awns 0.5–2.0 mm long, these with upward-pointed barbs, erect to slightly spreading at fruiting. Fruits 3–6 mm long, wedge-shaped to narrowly oblong-obovate, often slightly 3- or 4-angled (1 or both faces sometimes with a broad, low longitudinal angle or ridge), the angles with minute, stiff, ascending hairs, the faces reddish brown to black, moderately to densely pubescent with fine, more or less appressed hairs. 2n=24. August–October.

Scattered, mostly in the southern half of the Ozark Division and in counties bordering the Mississippi and Missouri Rivers (eastern U.S. west to Minnesota and Texas; Canada). Oxbows, swamps, bottomland forests, and margins of sinkhole ponds, sometimes epiphytic (see below).

This species frequently is found growing on mossy hummocks, rotting logs, and stumps, or as an epiphyte on the bases of Cephalanthus occidentalis (buttonbush, Rubiaceae), Nyssa aquatica (water tupelo, Cornaceae), Populus heterophylla (swamp cottonwood, Salicaceae), and Taxodium distichum (bald cypress, Cupressaceae). Steyermark (1963) noted two records from the Unglaciated Plains Division, collected at oxbow lakes in Bates and Vernon Counties. The specimens supporting these reports could not be located during the present research.