157. Bigelowia de Candolle in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 329. 1836.
Rayless-goldenrod [For Jacob Bigelow, 1787–1879, Massachusetts medical and botanical scholar]
Guy L. Nesom
Subshrubs, 30–70 cm (cespitose or colonial; caudices fibrous-rooted, short rhizomes or basal offsets). Stems erect, often subscapiform, early viscid, glabrous. Leaves basal (persistent rosettes); alternate; sessile; blades (3-nerved) linear to oblanceolate or spatulate, 4–14 cm, margins entire, faces gland-dotted (in pits); cauline linear, bractlike, abruptly or progressively reduced distally. Heads discoid, (in glomerate clusters) in compact to open, flat-topped, corymbiform arrays. Involucres cylindro-turbinate to cylindric, (4.5–9 ×) ca. 2 mm. Phyllaries 10–20 in 3–4 series, in vertical ranks, appressed (yellowish, sometimes green-tipped), 1-nerved (midnerves barely evident; weekly keeled) narrowly lanceolate to nearly linear, unequal, margins narrowly scarious, abaxial faces glabrous. Receptacles flat, pitted, epaleate. Ray florets 0. Disc florets 2–6, bisexual, fertile; corollas yellow, tubular, tubes shorter than or subequal to throats, lobes 5, recurved, lanceolate; style-branch appendages lanceolate. Cypselae turbinate to subcylindric, sometimes slightly compressed to nearly quadrate, 4–5-nerved (nerves thin, resinous), sparsely strigose; pappi persistent, of 40–50, tan, unequal, barbellate, apically attenuate bristles in 1(–2) series. x = 9.
Species 2 (2 in the flora): se United States.
Bigelowia is recognized by its leaves basally disposed or in basal rosettes, slender, subscapiform stems, and densely corymbiform arrays of small, cylindro-turbinate, discoid heads with phyllaries in vertical ranks and yellow corollas. Karyotypes of Bigelowia species, as well as various floral features, resemble those of Euthamia (L. C. Anderson 1970, 1972), and a hypothesis of relationship has been tentatively confirmed by molecular evidence (M. A. Lane et al. 1996). G. L. Nesom (1994) placed Bigelowia closest to Chrysoma, Euthamia, Gundlachia, and Xylothamia on the basis of morphologic evidence.
Anderson, L. C. 1970. Studies on Bigelowia (Astereae, Compositae). I. Morphology and taxonomy. Sida 3: 451–465. Anderson, L. C. 1972. Studies on Bigelowia (Asteraceae). II. Xylary comparisons, woodiness and paedomorphosis. J. Arnold Arbor. 53: 499–514. Anderson, L. C. 1977. Studies on Bigelowia (Asteraceae). III. Cytotaxonomy and biogeography. Syst. Bot. 2: 209–218.