Penstemon acaulis

Stems prostrate to ascending, to 1 cm (to 15 cm diam.), scabrous or puberulent. Leaves essentially basal, not leathery, scabrous; basal and proximal cauline sessile, 6–15(–22) × 0.6–1.3(–1.5) mm, blade linear, base tapered, margins entire, apex acute. Thyrses essentially absent, verticillasters 1, cymes 1(or 2)-flowered, 1 per node; proximal bracts linear, 5–10 × 0.6–1 mm; peduncles and pedicels glandular-pubescent and scabrous. Flowers: calyx lobes lanceolate, 3.5–5.5 × 0.8–1.5 mm, glandular-pubescent and scabrous; corolla lavender to blue or violet, without nectar guides, funnelform, 11–15 mm, yellowish or white-villous internally abaxially, tube 5–6 mm, throat gradually inflated, not constricted at orifice, 4.5–6 mm diam., slightly 2-ridged abaxially; stamens: longer pair reaching orifice or exserted, pollen sacs widely divergent or opposite, navicular, 0.7–0.9 mm, dehiscing completely, sutures papillate; staminode 7–9 mm, exserted, 0.4–0.5 mm diam., tip straight to slightly recurved, distal 4–7 mm densely pilose, hairs orange, to 0.8 mm; style 7–8 mm. Capsules 2.5–3.5 × 2.5–3 mm.

Phenology: Flowering May–Jul.
Habitat: Semi-barren rock ledges, clayey ridges, gravelly hilltops.
Elevation: 1500–2500 m.

Utah, Wyo.

Discussion

Penstemon acaulis is known from the Bridger Basin. Populations are reported from Daggett County, Utah, and Sweetwater County, Wyoming. E. C. Neese (1993) considered populations from Browns Park, Utah, to be transitional between P. acaulis and P. yampaënsis, treating the latter as P. acaulis var. yampaënsis (Penland) Neese. Some specimens from the vicinity of Clay Basin and Red Creek in northwestern Browns Park, Utah, are morphologically intermediate; other specimens from the same area can be assigned to species unambiguously. Given the morphologic distinctness of the majority of specimens, which fall into two basically discrete geographic regions, P. acaulis and P. yampaënsis are here treated as distinct, closely related species.

Selected References

None.

Lower Taxa