Subshrubs or, rarely, herbs, 0.1–0.6[–3] m. Roots with fusiform-tuberous thickenings [diffuse and without thickenings]. Leaves odd-pinnate, 2.5–15 cm; stipules subulate, 3–12 × 1 mm; petiole 0.5–3 cm, sericeous; rachis canaliculate; leaflets [3–]7–13[–27], petiolules 1 mm, glabrate, blades narrowly to widely elliptic, 10–100 × 3–50 mm (terminal leaflet distinctly larger), base and apex rounded, surfaces glabrate to densely sericeous, abaxial with reddish brown tannin deposits concentrated toward center of blade between veins. Racemes from axils of leaves on young twigs, rachis 1.5–3.5 times length of subtending leaf [much shorter to as long as subtending leaf], nodes [1–]20–30, internodes usually 3+ mm, axis usually sericeous; bracts caducous, linear-lanceolate, 2–10 × 1 mm. Pedicels [1.5–]2–4[–8] mm. Flowers: calyx tube 2–3 mm, usually sericeous to hispid, rarely glandular, lobes 2–3[–11] mm, abaxial longer than laterals, adaxial connate, more so than laterals; corolla usually whitish, [tinged pinkish or yellowish], 5–12 mm; filaments subequal. Legumes light to dark brownish, 30–55[–95] × 3–4[–7] mm, base blunt, not dorsiventrally constricted between seeds, with linear transverse impressions between seeds on lateral surface, apex acute, often terminating in persistent style base, usually glabrous or woolly, rarely glandular. Seeds 5–30. 2n = 16.

Phenology: Flowering mid–late summer.
Habitat: Open to closed under­story of pine-oak forests.
Elevation: 1300–2300 m.

Distribution

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Ariz., Mexico (Chihuahua, Durango, Sinaloa, Sonora).

Discussion

Variety sericea is distinguished geographically from var. caribaea by being the northernmost variety, confined to higher elevations in the understory of pine and oak woodlands of Arizona and adjacent Mexico in the Sierra Madre Occidental (M. Lavin 1988). Morpho­logically, var. sericea is distinguished by its often glan­dular inflorescence rachis, often with 20–30 nodes and a length of 1.5–3.5 times that of the subtending leaf. It is one of the forms of Coursetia caribaea that has leaves with more than seven leaflets, each of which forms dis­tinctive reticulate tannin deposits abaxially; the tannin deposits in this variety are consistently present as dark purple reticulations concentrated towards the center of the leaflets.

Plants from Puerto Rico and the Virgin Islands are referred to as var. caribaea, which is morphologically variable and widespread in Mesoamerica (M. Lavin 1988). In contrast with var. sericea in Arizona and adjacent Mexico, var. caribaea in the Antilles produces eglandular inflorescences distinctly shorter than the subtending leaf and leaflets that do not accumulate tannin deposits. Notably, var. caribaea extends from northern South America through the Lesser Antilles into Puerto Rico, the Virgin Islands, and Hispaniola. This species has not yet been recorded from Cuba and Jamaica in spite of its abundance in the Yucatán Peninsula (R. Duno de Stefano et al. 2010).

Selected References

None.

Lower Taxa

None.