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Herbs, annual or biennial; stems 30-70 cm tall, erect, striate, glabrous, corymbosely branched in upper 1/2. Middle stem leaves sessile; leaf blade ovate-oblong or oblong, 2-4 × 1-2.5 cm, both surfaces glabrous, 2-pinnatisect; ultimate segments narrowly linear. Distal stem leaves similar, gradually smaller. Capitula several to many, in an apical corymb, 2-3 cm in diam., pedunculate. Involucres hemispheric, 7-10 mm in diam.; phyllaries in 3 or 4 rows, margin narrowly white scarious, outer ones lanceolate, middle and inner ones oblong to oblanceolate. Ray florets white; lamina ca. 1 cm. Disk florets yellow, 5-lobed; lobes each with a resin sac. Achenes brown, triquetrous, ca. 2 mm, wrinkled, with 1 adaxial and 2 lateral thick whitish ribs, abaxially and apically with 2 distinct resin sacs. Corona short, subentire. Fl. and fr. Sep. 2n = 36.
Annuals (sometimes biennials or perennials), (5–)30–60(–80) cm. Stems 1, ascending to erect, usually branched distally, sometimes proximally, glabrous or glabrate (sparsely hairy when young). Leaf blades 2–8 cm, ultimate lobes filiform, 4–20 mm, not fleshy, apices apiculate. Heads (1–)10–200+, 3–4.5 cm diam., in corymbiform arrays of solitary heads at ends of branches. Phyllaries centrally dark greenish or brownish, oblong, subequal, scarious margins colorless to light brown, 0.1–0.2 mm wide. Ray florets 10–25; corollas (4–)10–13(–20) mm. Disc corollas 1–2.5 mm. Cypselae pale brown, ribs separated by 1/3+ their widths, abaxial-apical resin glands ± circular, faces minutely roughened between ribs. 2n = 18, 36.
A herb. It usually grows fresh from seed each year. It grows 30-60 cm tall. There is 1 stem that often branches towards the ends. The leaves are 2-8 cm long. The end lobes are narrow. There are 10-200 flowers in a head 3-4.5 cm across. The leaf-like structures under the flowers are dark green to brown.
