Linnaea 6: 511. 1831.
Annuals, perennials, or subshrubs, 10–70+ cm. Stems usually 1, erect, branched distally or ± throughout. Leaves mostly basal, basal and cauline, or mostly cauline; mostly opposite (distal rarely alternate); blades usually 1(–3)-pinnately lobed (ultimate lobes oblanceolate to filiform), faces usually glabrous, rarely hairy. Heads radiate or discoid, borne singly or in loose, corymbiform arrays. Calyculi of 3–8+ distinct, usually spreading or reflexed, usually linear to subulate, herbaceous bractlets. Involucres hemispheric to urceolate, 4–15+ mm diam. Phyllaries 5–8 in ± 2 series, persistent, connate 1/5–7/8+ their lengths, lance-ovate to ovate, ± equal, ± leathery to membranous, margins (of distinct apices) scarious. Receptacles flat to convex, paleate; paleae falling, (whitish with red-brown striae, each ± appressed to abaxial face of subtended cypsela), obovate to oblong, scarious. Ray florets 0 or ca. 8, neuter; corollas yellow or red-brown, or bicolored (yellow and red-brown). Disc florets 20–100+, bisexual, fertile; corollas yellow (with red-brown nerves) or red-brown, either with throats equal to or longer than 5, ± deltate, ± equal lobes, or with throats shorter than 5, ± lance-linear, ± unequal lobes (in either form, the abaxial sinus usually ± deeper than others). Cypselae (dark red-brown or stramineous) outer often arcuate, shorter, inner more columnar, usually some or all ± obcompressed (each usually shed together with its subtending palea), faces smooth or papillate to tuberculate or verrucate, margins sometimes ± winged; pappi 0, or persistent, of 2 retrorsely ciliate, subulate scales or awns. x = 12.
w North America, Mexico, South America.
Species 10+ (9 in the flora).
|1||Throats of disc corollas equal to or longer than lobes; pappi usually 0, rarely of 2 awns 0.1–0.3(–0.5) mm||> 2|
|1||Throats of disc corollas shorter than lobes; pappi usually of 2 awns or scales (0.5–)1–3 mm, rarely 0||> 4|
|2||Cauline leaves ± scattered over proximal 3/4+ of plant heights, internodes mostly 45–95 mm||Thelesperma simplicifolium|
|2||Cauline leaves ± crowded over proximal 1/4–1/2 of plant heights, internodes mostly 5–25+ mm or 1–5(–35) mm||> 3|
|3||Leaf lobes mostly linear to filiform, 5–25(–45+) × 0.5(–1) mm; cypselae 2–3 mm||Thelesperma longipes|
|3||Leaf lobes mostly oblanceolate to linear, (5–)10–35(–45+) × (1–)2–3(–5) mm; cypselae 5–7 mm||Thelesperma subnudum|
|4||Perennials (sometimes flowering first year); calyculi of 3–5+, ovate to oblong bractlets 1–3 mm; ray florets 0, or 8, laminae 4–8(–12+) mm; cypselae (4–)5–8 mm||> 5|
|4||Annuals (sometimes persisting); calyculi of 5–9, linear to narrowly triangular bractlets (2–)4–8+ mm; ray florets 8, laminae 10–20+ mm; cypselae 3.5–5.5+ mm||> 6|
|5||Plants 10–30(–50) cm; ray florets usually 8, rarely 0; disc corollas red-brown||Thelesperma ambiguum|
|5||Plants (20–)30–80+ cm; ray florets 0; disc corollas yellow||Thelesperma megapotamicum|
|6||Ray laminae proximally to wholly red-brown to purplish, or each with a proximal red-brown spot; disc corollas red-brown to purplish||> 7|
|6||Ray laminae yellow to golden (rarely proximally suffused with red-brown); disc corollas yellow or red-brown||> 8|
|7||Calyculi of 5–6(–9), linear to narrowly triangular bractlets (margins hispido-ciliate); cypselae 3.5–4 mm||Thelesperma burridgeanum|
|7||Calyculi of 6–7+, narrowly triangular bractlets (margins not ciliate); cypselae 5–5.5+ mm||Thelesperma nuecense|
|8||Plants 30–70(–120+) cm; cauline leaves ± scattered over proximal 9/10 of plant heights, internodes 35–100+ mm; disc corollas yellow, often with brown nerves||Thelesperma flavodiscum|
|8||Plants 10–40(–70+) cm; cauline leaves crowded to ± scattered over proximal 1/2–3/4+ of plant heights, internodes mostly 10–35(–50+ mm); disc corollas red-brown or yellow with red-brown nerves||Thelesperma filifolium|