Bull. Torrey Bot. Club 31: 643. 1905.
Stems erect, (13–) 19–42 cm, glabrous. Leaves basal and cauline, glabrous; basal and proximal cauline 13–57 × 4–19 mm, blade spatulate to oblanceolate, base tapered, apex mucronate, sometimes rounded to obtuse; cauline 3–7 pairs, sessile, 9–30 × 6–15 mm, blade oblanceolate to ovate, base clasping to cordate-clasping, apex acute to acuminate, sometimes mucronate. Thyrses interrupted or continuous, cylindric, 10–16 cm, axis glabrous, verticillasters (6–) 8–12, cymes 2–7-flowered, proximal bracts orbiculate to ovate, 11–18 × 6–14 mm; peduncles and pedicels glabrous. Flowers: calyx lobes lanceolate, 4–7 × 1.1–1.9 mm, margins erose, broadly scarious, glabrous; corolla lavender to lavender-blue, without nectar guides, funnelform, nearly rotate, 11–14 mm, glabrous externally or glandular, glabrous internally, tube 6.5–8 mm, throat gradually inflated, 4–5 mm diam., rounded abaxially; stamens: 4 prominently exserted (4–5 mm) beyond limb, pollen-sacs parallel, 1.2–1.5 mm, sutures smooth; staminode 6–7 mm, reaching orifice or exserted (adaxially), 0.4–0.5 mm diam., tip recurved, distal 1–2 mm densely villous, hairs golden yellow, to 0.8 mm; style 12–14 mm. Capsules 5–6 × 4–5 mm.
Phenology: Flowering May–Jul(–Sep).
Habitat: Sagebrush shrublands.
Elevation: 2100–2900 m.
Penstemon cyathophorus occurs mostly in Middle Park, North Park, and the southern end of the North Platte River valley in the Southern Rocky Mountains. Populations have been documented in Grand, Jackson, and Summit counties, Colorado, and Carbon County, Wyoming. Besides having all four stamens prominently exserted, P. cyathophorus is unique in Penstemon in having the distal end of the staminode situated against the adaxial surface of the throat in mature corollas; it is situated against the abaxial surface in other species of Penstemon.
"/4+timescorollathroat" is not declared as a valid unit of measurement for this property.