Herbs, annual, herbage usually drying dark. Stems erect, (10–)20–250(–320) mm, nodes 3–6, internodes 1–6 mm, glandular-pubescent to glandular-villous. Leaves usually cauline, relatively even-sized or reduced distally; petiole absent, bases of largest leaves often long-tapered to petiole-like extensions; blade obovate, elliptic, or oblanceolate, (5–)7–35(–50) × (2–)3–18(–26) mm, margins entire, rarely toothed, plane, apex abruptly acuminate, acute-acuminate, or cuspidate to long-tapering or long-acuminate, surfaces glandular-pubescent. Pedicels 1–4(–8) mm in fruit. Flowers 2 per node, or 1 or 2 per node on 1 plant, chasmogamous. Calyces symmetrically attached to pedicels, inflated in fruit, 6–13(–15) mm, glandular-pubescent, tube strongly plicate, lobes slightly recurved, narrowly triangular, subequal, often slightly indurate, apex acuminate to attenuate, ribs broad, darkened, blackish, thickened, strongly raised, intercostal areas whitish, membranous. Corollas magenta with dark reddish spot on each side of mouth on interior lateral walls of throat, usually with reddish lines extending from throat onto midveins of lobes, throat floor yellow with reddish speckling and variable reddish markings, palate ridges yellow, tube-throat (9–)12–22 mm, limb 12–24 mm diam., not bilabiate. Anthers included, glabrous, sometimes ciliate. Styles glandular-puberulent. Stigmas included, lobes equal. Capsules (6–)7–13(–15) mm.
Ariz., Calif., Nev., Utah
Varieties 2 (2 in the flora).
Diplacus bigelovii is distributed in southeastern California from southern Mono County south to Imperial and San Diego counties through southern Nevada into Washington County, Utah, and La Paz and Mohave counties, Arizona. The relatively sharp line dividing the two varieties roughly follows the Inyo-San Bernardino county line, then cuts across Clark County, Nevada, and Mojave County, Arizona.
Diplacus bigelovii can generally be recognized by its relatively large, nearly radially symmetric corollas, included stigmas, and inflated mature calyces with lobes of unequal length and apices acuminate-attenuate. The two varieties have distinctive leaf shapes; D. M. Thompson (2005) reported them as very closely parapatric and exhibiting limited intergradation near their contiguous occurrence.
|1||Leaf blades: distals gradually narrower than proximals, apices long-tapering or long-acuminate; internodes: proximals usually longer than distals.||Diplacus bigelovii var. bigelovii|
|1||Leaf blades: distals usually relatively broader than proximals, apices abruptly acute-acuminate, sometimes cuspidate; internodes usually subequal.||Diplacus bigelovii var. cuspidatus|