Penstemon sect. Ambigui

(Rydberg) Pennell
Contr. U.S. Natl. Herb. 20: 326, 333. 1920.
Basionym: Penstemon [unranked] Ambigui Rydberg Fl. Colorado, 306. 1906
Treatment appears in FNA Volume 17. Treatment on page 94. Mentioned on page 92, 95.

Subshrubs. Stems glabrous, glabrate, or scabrous proximally, not glaucous. Leaves cauline, opposite, not leathery, glabrous or scabrous, not glaucous; cauline sessile, blade linear, margins entire. Thyrses interrupted, cylindric to conic, axis glabrous or scabrous, cymes 2 per node; peduncles and pedicels spreading or ascending. Flowers: calyx lobes: margins entire or erose, broadly scarious, glabrous; corolla pink or lavender to violet, bilaterally symmetric, bilabiate, not personate, salverform or funnelform, glabrous externally, glandular-pubescent internally abaxially, throat slightly inflated, not constricted at orifice, rounded abaxially; stamens included or longer pair reaching orifice or barely exserted, filaments glabrous, pollen sacs divergent, explanate, dehiscing completely, connective splitting, sides glabrous, sutures smooth; staminode included, terete or slightly flattened distally, 0.1 mm diam., tip straight, glabrous; style glabrous. Capsules glabrous. Seeds dark brown to reddish brown, angled, 1–2.8 mm.

Distribution

w United States, n Mexico.

Discussion

Species 2 (2 in the flora).

Section Ambigui includes two subshrubby species of the southwestern and south-central United States and northern Mexico.

Selected References

None.

Key

1 Corollas salverform, (14–)16–22(–28) mm. Penstemon ambiguus
1 Corollas funnelform, 8–14 mm. Penstemon thurberi