P. Browne

Civ. Nat. Hist. Jamaica, 312, plate 33, fig. 1. 1756.

Common names: Threefold
Etymology: Greek trixos, 3-fold, describing the 3-cleft corolla
Treatment appears in FNA Volume 19. Treatment on page 75. Mentioned on page 12, 14, 59, 70, 71, 73, 76.

Shrubs [herbs], 20–300+ cm (often rhizomatous, stems hairy, hairs gland-tipped and glandless). Leaves cauline; sessile or petiolate; blades elliptic, lanceolate, linear, or linear-lanceolate, bases cuneate, margins dentate or entire, faces (at least abaxial) usually glandular and ± strigose. Heads quasi-radiate (see florets), borne singly or in corymbiform or paniculiform arrays. Involucres ± cylindric, 12–15 mm (subtended by calyculi of 3–7 spreading or ascending bractlets). Phyllaries (reflexed in fruit) in 1–2 series, linear (± keeled), apices acute. Receptacles flat, smooth, hairy, epaleate. Florets 4–25[–60], bisexual, fertile; corollas yellow (aging white), zygomorphic (2-lipped; outer lip liguliform, lobes 3, lance-deltate, inner lip smaller, lobes ± filiform, recurved); anther basal appendages entire, apical appendages oblong, acute; style branches relatively short, apices truncate-penicillate. Cypselae subcylindric to fusiform, often ± beaked, ribs 5, faces glandular-hairy; pappi of 60–80+ dull white [tawny], finely barbed bristles. x = 9.


North America, Mexico, West Indies, Central America, South America.


Species ca. 65 (2 in the flora).


1 Leaves usually ascending, almost parallel with stems, stomates on both faces, induments: abaxial faces glandular and sparsely strigose (sometimes only on veins), adaxial faces glandular and strigose to pilose; papilla-like double hairs of cypselae producing mucilage when wetted Trixis californica
1 Leaves usually spreading, stomates on abaxial faces, induments: margins and, sometimes, abaxial midveins with glandless and glandular hairs, otherwise glabrous; papilla-like double hairs of cypselae not producing mucilage when wetted Trixis inula