Smithsonian Contr. Knowl. 5(6): 78. 1853.
Annuals, 30–200 cm. Stems glabrous. Leaves: proximal usually persistent at flowering, cauline blades obscurely (1-), 3-nerved, or 5-nerved, mostly narrowly elliptic-lanceolate, 40–70 × 2–4 mm, reduced distally. Heads usually in open arrays. Involucres campanulate, 4.5–7.5 mm diam. Phyllary apices conduplicate, swollen (appearing abaxially keeled). Ray-florets 8–19; corollas yellow, 5–12 mm. Disc-florets (30–) 40–60. Cypselae 0.7–2 mm, faces (pebbly or warty with raised, blisterlike oil cavities) glabrous; pappi coroniform, 0.1–0.2 mm (margins entire or obscurely denticulate or erose). 2n = 8.
Phenology: Flowering Jul–Oct(–Nov).
Habitat: Meadows and clearings in pine, pine-oak, and pine-fir woods, ditches, road cuts, alluvium
Elevation: 1800–2800 m
Ariz., N.Mex., Mexico (Chihuahua), Mexico (Sinaloa), Mexico (Sonora)
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