Annuals, biennials, perennials, subshrubs, shrubs, or treelets, 1–80(–300) cm (some rhizomatous or with woody caudices). Leaves basal, basal and cauline, or cauline; opposite or alternate; usually petiolate, sometimes sessile; blades mostly cordate, deltate, elliptic, lanceolate, linear, oblanceolate, oblong, obovate, ovate, rhombic, or spatulate, often 1–2-pinnately or -ternately lobed (lobes mostly filiform to linear, lanceolate, or oblanceolate), ultimate margins entire or toothed, faces ± lanate to woolly, or hispidulous to scabrellous or strigose, sometimes glabrescent, sometimes stipitate-glandular, rarely glabrous, often gland-dotted. Heads usually radiate, sometimes discoid, rarely radiant (Chaenactis spp.), borne singly, or in clusters, or in corymbiform, cymiform, or paniculiform arrays. Calyculi usually 0 (sometimes 1–3 bractlets in Schkuhria). Involucres campanulate to narrowly cylindric or obconic, or hemispheric to rotate. Phyllaries usually persistent, 4–60+ in 1–4+ series (usually erect at flowering, usually reflexed in fruit, usually distinct, basally coherent in some Arnica spp., mostly lance-ovate, linear, or ovate, unequal to subequal, mostly herbaceous to membranous, outer foliaceous in Venegasia). Receptacles conic, flat, or hemispheric, often knobby or pitted (sometimes hairy or gland-dotted), usually epaleate (paleae sometimes subulate scales in Chaenactis; in Bartlettia, linear, membranous, hairy scales, each appressed to and shed with an associated cypsela may be interpreted as paleae). Ray florets 0 (corollas of peripheral florets sometimes notably larger than those of the inner, then zygomorphic, showy, and somewhat raylike, e.g., Chaenactis spp.) or (1–)4–21(–60+), pistillate, fertile; corollas yellow, orange, red, purplish, or whitish (persistent, marcescent in Arnica dealbata). Disc florets 4–200+, usually bisexual, fertile (functionally staminate in Arnica dealbata); corollas yellow, orange, purplish, or whitish, usually hairy and/or gland-dotted or stipitate-glandular, tubes shorter than to longer than cylindric or campanulate to funnelform throats, lobes 5, deltate to linear; anther thecae pale; stigmatic papillae in 2 lines. Cypselae mostly obpyramidal and 4–5-angled, sometimes clavate, columnar, cylindric, or fusiform, sometimes compressed and ± linear (e.g., Chaenactis, Hulsea) or obcompressed (e.g., Arnica dealbata, Bartlettia; lengths usually 3+ times diams.), faces usually hairy and/or gland-dotted; pappi falling, fragile, or persistent, usually of 6–80 distinct or basally connate bristles, or of 4–20 distinct (or basally connate) scales, all, some, or none aristate, sometimes pappi none.

Distribution

North America, Mexico, Central America, South America (Bahia).

Discussion

Genera 25, species 129 (19 genera, 83 species in the flora).

The circumscription of Chaenactidinae used here (that of H. Robinson 1981) contrasts sharply with that of B. G. Baldwin (Baldwin and B. L. Wessa 2000; Baldwin et al. 2002). Baldwin included Chaenactis, Dimeresia (here segregated in Dimeresiinae), and Orochaenactis in his Chaenactidinae (as sole subtribe in his Chaenactideae) and placed other genera of Chaenactidinae in the sense of Robinson as follows: Amauriopsis, Bahia, Bartlettia, Chamaechaenactis, Florestina, Hymenothrix, Palafoxia, Peucephyllum, Picradeniopsis, Platyschkuhria, Psathyrotopsis, and Schkuhria in Bahiinae (in Bahieae); Arnica in Arnicinae (in Madieae); Hulsea in Hulseinae (in Madieae); Syntrichopappus in Baeriinae (in Madieae); Venegasia in Venegasiinae (in Madieae); and Jamesianthus in Pectidinae (in Tageteae).

Selected References

None.

Lower Taxa

Amauriopsis, Arnica, Bahia, Bartlettia, Chaenactis, Chamaechaenactis, Florestina, Hulsea, Hymenothrix, Jamesianthus, Orochaenactis, Palafoxia, Peucephyllum, Picradeniopsis, Platyschkuhria, Psathyrotopsis, Schkuhria, Syntrichopappus, Venegasia

Key

1	Pappi wholly or partially of bristles (pappi 0 and ray corollas whitish with red veins in Syntrichopappus lemmonii)	> 2
1	Pappi none or wholly of scales (all, some, or no scales aristate)	> 7
2	Leaves all or mostly opposite	> 3
2	Leaves mostly alternate (sometimes mostly basal)	> 4
3	Phyllaries 8–23 in (1–)2 series (subequal); pappi persistent, of 10–50 bristles	Arnica
3	Phyllaries 14–18+ in ± 3 series (unequal); pappi fragile, of 6–8+ bristles	Jamesianthus
4	Shrubs or treelets; leaf blades linear-filiform	Peucephyllum
4	Annuals or perennials; leaf blades mostly deltate, elliptic, or rhombic	> 5
5	Cypselae obcompressed (each shed together with a subtending, linear, membranous scale, margins ciliate)	Bartlettia
5	Cypselae clavate, fusiform, obconic, or obpyramidal (margins not ciliate)	> 6
6	Ray florets 5–8; pappi 0, or ± fragile (falling in whole of fragmented rings), of 25–40 basally connate or coherent bristles in 1–2 series	Syntrichopappus
6	Ray florets 0; pappi persistent, of 70–90 distinct, unequal bristles in 2–3series	Psathyrotopsis
7	Leaves all or mostly cauline, usually all or mostly opposite (distal sometimes, usually in Bahia, alternate)	> 8
7	Leaves all or mostly basal, or mostly cauline, mostly alternate (proximal sometimes opposite)	> 11
8	Leaves woolly; rays 5–12 (corollas persistent, marcescent); disc florets usually functionally staminate; cypselae obovoid or plumply fusiform, smooth or ca. 20-ribbed	Arnica
8	Leaves usually ± hairy (not woolly, hairs white, straight, often bulbous, conic, or fusiform, 0.1–0.8 mm), sometimes glabrous, sometimes stipitate-glandular, usually gland-dotted; rays 0, or 1–15 (corollas withering, not marcescent); disc florets bisexual, fertile; cypselae obpyramidal, mostly 4-angled	> 9
9	Phyllaries 4–9(–12, margins often purplish or yellowish)	Schkuhria
9	Phyllaries 6–18+ (margins rarely purplish, not yellowish)	> 10
10	Annuals, biennials, or perennials, 10–80+ cm; leaves all or mostly opposite (if perennials, blades lanceolate to oblong, 2–20+ mm wide), or all ormostly alternate	Bahia
10	Perennials, 3–20+ cm; leaves all or mostly opposite (blades or lobes lanceolate to lance-linear, mostly 1–8 mm wide)	Picradeniopsis
11	Phyllaries 20–40+ in 3–4+ series (unequal, outer spreading or reflexed at flowering, rotund to broadly ovate, foliaceous)	Venegasia
11	Phyllaries mostly 4–21(–60+ in Hulsea; subequal to unequal, all ± erect at flowering, mostly lanceolate, linear, oblanceolate, obovate, or spatulate, not foliaceous)	> 12
12	Disc corolla lobes lance-linear, lance-oblong, or linear (lengths mostly 2+ times widths)	> 13
12	Disc corolla lobes mostly deltate, lance-deltate, lanceolate, or ovate (lengths mostly 1–2 times widths, sometimes longer in zygomorphic corollas of some Chaenactis spp.)	> 15
13	Pappus scales 12–18	Hymenothrix
13	Pappus scales 4–12	> 14
14	Leaf blades broadly lanceolate to linear (not lobed); corollas usually pinkish or purplish, sometimes whitish; cypselae densely to sparsely hairy (hairs straight)	Palafoxia
14	Leaf blades (at least mid-cauline) 3- or 5-lobed or -foliolate (blades or leaflets broadly to narrowly oblong to ovate); corollas whitish; cypselae sparsely hairy (hairs curled)	Florestina
15	Leaves sparsely to densely hirtellous, scabrellous, or strigose (hairs white, straight, often conic or fusiform, 0.1–0.8 mm), sometimes glabrescent, sometimes stipitate-glandular, usually gland-dotted; cypselae obpyramidal, 4-angled	> 16
15	Leaves mostly sparsely lanate, tomentose, or woolly (hairs crisped, tangled or matted, mostly 0.8+ mm), sometimes glabrescent, or finely granular-pubescent (hairs bulbous, less than 0.2 mm), or glabrous, sometimes stipitate-glandular or gland-dotted; cypselae clavate, ± cylindric, or obconic, often compressed and ± linear, obscurely, if at all, 4-angled (sometimes obscurely 8–20-angled)	> 18
16	Leaves mostly cauline, blades deltate, oblong, or ovate overall, usually 1–2-ternately lobed	Amauriopsis
16	Leaves mostly basal or basal and cauline, blades cordate, elliptic, lanceolate, ovate or rounded	> 17
17	Plants mostly 10–50+ cm; leaf blades mostly lanceolate, sometimes ± ovate; heads borne singly or in corymbiform to paniculiformarrays; rays 6–12	Platyschkuhria
17	Plants 2–7(–9) cm (10–20+ cm across); leaf blades cordate, elliptic,ovate, or rounded; heads borne singly; rays 0	Chamaechaenactis
18	Ray florets 9–60+	Hulsea
18	Ray florets 0 (corollas of peripheral florets sometimes zygomorphic and larger than inner, heads radiant)	> 19
19	Heads borne singly or in ± cymiform arrays; disc florets 8–70+	Chaenactis
19	Heads borne singly or (2–5) in clusters (at stem tips); disc florets 4–9	Orochaenactis