Herbs, multi-stemmed, 0.5–2 dm; roots with bright red to orange cortex, loosely exfoliating in thin layers. Stems spreading to erect, pubescent, hairs incurved and appressed. Leaves subsessile or petiolate, petiole to 3 mm; blade ovate, lanceolate, elliptic, or linear, 5–35(–40) × 1–9 mm, base rounded to cuneate, apex acute to rounded or acuminate, surfaces subglabrous or pubescent, hairs incurved. Racemes terminal, usually leaf-opposed, sometimes near stem base, 0.8–5(–6) × 1–2.5 cm; rachis not thorn-tipped; peduncle 0–0.5 cm; bracts persistent, elliptic, ovate, or lanceolate. Pedicels 1.5–4 mm, pubescent or glabrous. Flowers pink to cream, wings sometimes greenish, (4.4–)5–7.5 mm; upper sepal persistent, others deciduous, ovate, lower sepals ovate to elliptic or obovate, (1.6–)1.9–4.1 mm, pubescent or glabrous; wings obovate to elliptic, 3–7 × 1.4–3.2 mm, pubescent or glabrous; keel 2.7–6.1 mm, sac usually glabrous, rarely sparsely incurved-pubescent distally, beak oblong or bluntly rounded, (0.2–)0.6–1.7 × 0.2–0.8 mm (rarely absent in var. tamaulipana), glabrous or pubescent. Capsules ellipsoid, sometimes broadly so, 3.7–6.2 × 2.4–4.3 mm, base subtruncate to acute, margins with very narrow wing or not winged, pubescent. Seeds 2.7–4.9 mm, densely pubescent; aril 1.3–2.6 mm, lobes to 1/2 length of seed.

Distribution

Texas, n Mexico.

Discussion

Varieties 4 (2 in the flora).

Rhinotropis nitida is closely related to R. lindheimeri, with seven varieties recognized between the two. According to T. L. Wendt (1978), although the differences between the two species are fairly small, the recognition of a single species would obscure the differences in the evolution of several superficially similar taxa.

Selected References

None.

Lower Taxa

Rhinotropis nitida var. goliadensis, Rhinotropis nitida var. tamaulipana

Key

1	Stems spreading to erect, hairs mostly 0.15–0.3 mm, usually spreading to loosely incurved, tips not close to stem surface; leaf blades elliptic to ovate in proximal 1/3 of stem, length 1.5–3 times width, distal leaves similar or somewhat narrower, not lanceolate or linear; pedicels (2–)2.5–4 mm.	Rhinotropis nitida var. goliadensis
1	Stems erect, hairs mostly 0.07–0.1(–0.15) mm, closely incurved-appressed, very close to stem, tips touching stem surface; leaf blades narrowly elliptic to lanceolate or linear, including basal ones, length at least 5 times width, or when leaves in proximal 1/3 of stem are broader, then distal leaves lanceolate-elliptic, much narrower than proximal ones; pedicels 1.5–3 mm.	Rhinotropis nitida var. tamaulipana