391. Marshallia Schreber, Gen. Pl. 2: 810. 1791.
Barbara’s buttons [For Moses Marshall, 1758–1813, American botanist, nephew of and assistant to Humphrey Marshall]
Linda E. Watson
Perennials, (10–)20–80(–120) cm (fibrous-rooted, usually with caudices, sometimes rhizomatous). Stems erect, sometimes branched (striate). Leaves basal and/or cauline; alternate; petiolate or sessile; blades (1- or 3-nerved) elliptic, linear, linear-elliptic, linear-oblanceolate, oblanceolate, ovate, or spatulate, margins entire, faces glabrous. Heads discoid, borne singly or in open, corymbiform arrays (peduncles relatively long). Involucres hemispheric to obconic, 10–25+ mm diam. Phyllaries persistent, 12–24 in ± 2 series (lanceolate, linear, oblong, ovate, or rhombic, subequal, herbaceous, midnerves often keeled, proximal margins often scarious). Receptacles conic or convex (usually hollow), paleate (paleae linear to spatulate, distally herbaceous). Ray florets 0. Disc florets (20–)45–90(–160+), bisexual, fertile; corollas pale lavender, pink, or purple, or white, (usually hairy) tubes longer than to nearly equaling throats, lobes 5, lance-linear to linear-oblong (often contorted). Cypselae turbinate or clavate (5-angled, ribs 10, often hairy); pappi persistent, of 5(–6) scarious to membranous (hyaline, sometimes scaberulous) scales. x = 9.
Species 7 (7 in the flora): s, c, se United States.
SELECTED REFERENCES
Channell, R. B. 1957. A revision of the genus Marshallia (Compositae). Contr. Gray Herb. 81: 41–132. Watson, L. E. and J. R. Estes. 1990. Biosystematic and phenetic analysis of Marshallia (Asteraceae). Syst. Bot. 15: 403–414.
