Sp. Pl. 2: 921. 1753.
Gen. Pl. ed. 5, 392. 1754.
Annuals, perennials, or subshrubs, 5–50(–150+) cm. Stems erect or prostrate. Leaves cauline; opposite; petiolate (petioles usually winged) or sessile; blades deltate, lance-elliptic, lanceolate, lance-linear, linear, linear-oblong, ovate, or rhombic, sometimes pinnately lobed, ultimate margins entire or toothed, faces usually hairy, usually gland-dotted (at least abaxial). Heads radiate, borne singly (from forks of branches, peduncles often uncinate). Involucres mostly hemispheric (sometimes ± cupulate), [4–]5–20(–30+) mm diam. Phyllaries persistent (outer) or falling with cypselae, 8–20+ in 2 series (outer [2–]5 often ± connate, herbaceous, inner each investing a ray ovary, forming a perigynium, shed with enclosed cypsela). Receptacles flat or convex to conic (their tips, paleae, and spent florets often shed as a unit), paleate (paleae lanceolate to linear, scarious, conduplicate, often with dilated, erose tips). Ray florets [3–]5–13+, pistillate, fertile; corollas yellow, orange, or cream-white, sometimes purplish abaxially (tubes often wanting). Disc florets [3–]45–70[–100+], functionally staminate; corollas ochroleucous, yellow, or orange, tubes shorter than funnelform throats, lobes 5, ± deltate. Cypselae each enclosed within and shed with a smooth, sculpted, or tuberculate, scarious, coriaceous, or hardened perigynium (the ultimate “fruits” ± compressed, ± D-shaped); pappi 0. x = 12.
United States, Mexico, West Indies, Central America, South America, introduced in Old World.
Species ca. 36 (7 in the flora).
|1||Perennials; ray corollas cream-white||> 2|
|1||Annuals; ray corollas yellow to yellow-orange||> 3|
|2||Outer phyllaries connate 1/2–3/5 their lengths; ray laminae 7–13 × 2.5–8 mm||Melampodium leucanthum|
|2||Outer phyllaries connate 1/6–1/3+ their lengths; ray laminae 2–8+ × 1–3+ mm||Melampodium cinereum|
|3||Leaf blades deltate or rhombic to lanceolate, lengths 1–2(–3) times widths||> 4|
|3||Leaf blades lance-elliptic or oblanceolate to linear, lengths (3–)4–8+ times widths||> 5|
|4||Outer phyllaries ovate, 3.5–6 mm, connate 1/4–1/3 their lengths; disc florets 40–70+; fruits 2.8–4 mm||Melampodium divaricatum|
|4||Outer phyllaries oblong-elliptic, (6–)8–15+ mm, connate 0–1/6 their lengths; disc florets 30–45; fruits 4–7 mm||Melampodium perfoliatum|
|5||Outer phyllaries connate 3/5–2/3 their lengths; disc florets 25–40||Melampodium appendiculatum|
|5||Outer phyllaries connate 0–1/6 their lengths; disc florets 4–10||> 6|
|6||Peduncles 4–30+ mm; rays 7–12, laminae 1.2–1.5 mm; disc florets 8–10||Melampodium longicorne|
|6||Peduncles 0–3(–12+) mm; rays 5–8, laminae 0.6–1.1 mm; disc florets 4–6||Melampodium strigosum|