Penstemon sect. Bridgesiani
Contr. U.S. Natl. Herb. 20: 327, 335. 1920.
Subshrubs. Stems scabrous proximally, glabrous distally, sometimes wholly glabrous, glaucous or not. Leaves mostly cauline, basal usually absent or greatly reduced, opposite, leathery or not, glabrous, not glaucous; basal and proximal cauline petiolate; cauline petiolate, blade oblanceolate, lanceolate, or linear, margins entire. Thyrses interrupted, secund, axis glabrous proximally, glandular-pubescent distally, cymes 2 per node; peduncles and pedicels ascending. Flowers: calyx lobes: margins entire, herbaceous or narrowly scarious, glandular-pubescent; corolla red to scarlet, bilaterally symmetric, strongly bilabiate, not personate, salverform, glandular-pubescent externally, hairy internally abaxially, throat slightly inflated, not constricted at orifice, slightly 2-ridged abaxially; stamens: longer pair exserted (concealed by galeate adaxial lobes), filaments glabrous, pollen sacs parallel, saccate, dehiscing incompletely, distal 2/3–3/4 indehiscent, connective splitting, sides glabrous, sometimes scabrellous near filament attachment, sutures denticulate, teeth to 0.1 mm; staminode included, terete, 0.1–0.2 mm diam., tip straight, glabrous; style glabrous. Capsules glabrous. Seeds light brown to brown, angled, 0.9–1.9 mm.
w United States, nw Mexico.
Penstemon rostriflorus was included in sect. Saccanthera by D. D. Keck (1932). Molecular data (C. A. Wessinger et al. 2016) provided evidence for placing P. rostriflorus near sect. Saccanthera.