Trans. Amer. Philos. Soc., n. s. 7: 298. 1840.
Perennials, 10–160 cm (usually cespitose, induments usually of stipitate-glandular and smooth-surfaced, curved or twisted woolly hairs, plants with caudices or short rhizomes, roots fibrous). Stems ascending or erect, simple, glabrate, puberulent, pilose, cottony, or woolly, eglandular or glandular. Leaves cauline; alternate; sessile (proximal withering by flowering; proximalmost reduced, scalelike); blades (1-nerved) ovate, elliptic, oblong, lanceolate, or linear (± uniform in size), margins entire, faces glabrate, scabrous, cottony, or woolly, eglandular or stipitate-glandular. Heads radiate or discoid, usually in open, racemiform, paniculiform, or corymbiform arrays, sometimes borne singly. Involucres turbinate-cylindric, turbinate, turbinate-obconic, or campanulate, 10–25 mm diam. Phyllaries 20–50 in 3–6 series, ± unequal (± appressed, often reddish or purplish at margins and tips), 1-nerved (keeled), ovate, lance-oblong, lanceolate, linear-oblong, or linear, chartaceous at bases, margins sometimes hyaline, especially proximally; apices acute to obtuse, green, usually puberulent, tomentose, and/or stipitate-glandular, sometimes glabrous. Receptacles ± flat, pitted, epaleate. Ray florets 0–21 (usually 5, 8, or 13), pistillate, fertile; corollas violet-purple, purple, pink, or white. Disc florets 10–35, bisexual, fertile; corollas yellow, ± ampliate, tubes shorter than funnelform throats, lobes 5, erect or reflexed, triangular; style-branch appendages lanceolate. Cypselae ± obconic, flattened, laterally 1–2-ribbed, sometimes with 1–2 additional nerves on each face, glabrous, pilose, or strigose, eglandular; pappi persistent, of 30–50 whitish to tawny, barbellate or smooth, apically clavate or more conspicuously barbellate bristles in 2(–3) series (outer usually 1 mm or less, sometimes 0, inner 5–10 mm). x = 9.
Species 10 (10 in the flora).
Eucephalus, a relatively well-marked western North American group, has been treated as a section of Aster or as a distinct genus. Recent molecular evidence places Eucephalus, together with the eastern North American Doellingeria, at the base of the North American clade of Astereae.
|1||Ray florets usually 1–4, often 0||> 2|
|1||Ray florets commonly 5, 8, or 13+||> 5|
|2||Ray florets 0; leaves 5–9 cm, ± glabrous abaxially, glandular adaxially; plants 60–120 cm; open woods, Lane County, Oregon||Eucephalus vialis|
|2||Ray florets usually 1–4; leaves 2–6 cm, hairy; plants 10–100 cm||> 3|
|3||Leaves glabrous or nearly so abaxially, moderately to densely hairy adaxially||Eucephalus tomentellus|
|3||Leaves glabrous, eglandular or sparsely glandular on both faces||> 4|
|4||Phyllaries subequal||Eucephalus breweri|
|4||Phyllaries strongly unequal||Eucephalus glabratus|
|5||Stems, leaves, and phyllaries glabrous, glaucous; plants 40–160 cm; leaves linear tonarrowly lance-elliptic, 4–10 cm; rays purple||Eucephalus glaucescens|
|5||Stems, leaves, and phyllaries pubescent or glabrate, glandular or not, not glaucous; plants 10–120(–150) cm; leaves elliptic, oblong, lance-ovate, lance-elliptic, lanceolate, linear-oblong or -lanceolate, 1.5–10 cm; rays white, pink, violet, or purple.||> 6|
|6||Leaves 5–10 cm, elliptic to lanceolate, glabrous and eglandular, or abaxially ± glandular and/or villous; plants 50–150 cm; rays white to pink||Eucephalus engelmannii|
|6||Leaves 1.5–7 cm, elliptic, elliptic-oblong, oblong, lance-ovate, lance-elliptic, linear-oblong or -lanceolate, glandular or not, scabrous or cottony; plants 10–80 cm; rays white or violet to purple||> 7|
|7||Rays white; stems pilose or sparsely to moderately glandular-pubescent||> 8|
|7||Rays violet to purple; stems scabrous (to scabrellous) or cottony and/or glandular-pubescent (especially peduncles)||> 9|
|8||Phyllaries lance-ovate; Cascade Mountains, Oregon||Eucephalus gormanii|
|8||Phyllaries lance-linear; Olympic Mountains, Washington||Eucephalus paucicapitatus|
|9||Leaves moderately scabrellous (and sometimes glandular) on both faces||Eucephalus elegans|
|9||Leaves sparsely scabrous abaxially, strongly cottony adaxially||Eucephalus ledophyllus|