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FNA | Family List | FNA Vol. 20 | Asteraceae | Senecio

22. Senecio integerrimus Nuttall, Gen. N. Amer. Pl. 2: 165. 1818.

Perennials (possibly biennials), (10–)20–70 cm (cau­dices button­like, roots fleshy-fibrous). Herbage arachnose, loosely tomentose, or villous (hairs crisped, jointed), glabrescent. Stems single. Leaves progressively reduced distally; ± petiolate; blades elliptic, lanceolate, linear, oblanceolate, rounded-deltate, or suborbiculate, 6–25 × 1–6 cm, bases ± tapered or truncate to cordate, margins entire or ± dentate (distal leaves sessile, bractlike). Heads 6–20(–40+) in corymbiform arrays (peduncle of terminal head often shorter than others). Calyculi of 1–5+ linear to filiform bractlets (seldom more than 2 mm). Phyllaries usually ± 13 or ± 21, rarely ± 8, (4–)5–12(–15) mm, tips usually black, sometimes green. Ray florets usually ± 8 or ± 13, sometimes 0; corolla laminae 6–15(–20) mm (usually yellow, ochroleucous to white in one variety). Cypselae usually glabrous, sometimes hirtellous (mostly on angles). 2n = 40, 80.

Varieties 5 (5 in the flora): c, w North America.

The varieties of Senecio integerrimus are distinguished by morphology and geography.

1 Basal leaves with distinct petioles, blades usually ovate to rounded-deltate, sometimes obovate to oblanceolate; ray corollas white or ochroleucous   22b Senecio integerrimus var. ochroleucus
+ Basal leaves with or without distinct petioles, blades elliptic, lanceolate, oblanceolate, rounded-deltate, sublinear, or suborbiculate; ray corollas yellow (or rays 0)   (2)
2 (1) Herbage glabrous or glabrate at flowering (except in leaf axils and among heads); phyllaries linear-subulate, tips usually green, minutely (if at all) black   22a Senecio integerrimus var. integerrimus
+ Herbage usually arachnose, tomentose, or villous at flowering; phyllaries lanceolate to linear-subulate, tips black (if minutely so, then narrowly lanceolate and broader than subulate)   (3)
3 (2) Basal and proximal leaves oblong or lanceolate to sublinear; heads 3–6(–16+); phyllaries 10–15+ mm   22c Senecio integerrimus var. scribneri
+ Basal and proximal leaves mostly elliptic to oblanceolate, sometimes elliptic or rounded-deltate to suborbiculate; heads usually 6–15(–30+; if fewer than 6, leaves lanceolate or broader); phyllaries 5–12 mm.   (4)
4 (3) Plants copiously arachnose, tomentose, or villous at flowering; phyllaries linear-subulate, 8–12 mm, tips minutely, if at all, blackened   22d Senecio integerrimus var. major
+ Plants copiously to sparsely arachnose, tomentose, or villous at flowering; phyllaries mostly lanceolate (seldom as narrow as linear-subulate), 5–10 mm, tips black   22e Senecio integerrimus var. exaltatus


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