Astragalus nigrocalyx Slobodov ex Grig.

Khan, Amjad, Sultan, Amir, Mumtaz, Abdul Samad, Bagheri, Ali, Khan, Nazar & Khan, Tahir, 2025, Contribution to the Astragalus sect. Aegacantha from Pakistan, with the description of a new species and a new record, Phytotaxa 698 (2), pp. 101-120 : 110-111

Astragalus nigrocalyx Slobodov ex Grig. , in Fl. Tadzhik. 5: 674. 1937, ( Figs. 8‒9 )

Holotype: Tadzhikistan, Gorno-Badakhshan, Darwaz occ., trajectus Ravnou , 4 October, 1932, N. F. Gontscharov & et al. 1006 ( LE!).

Description

Spiny shrub, 20–45 cm tall, mostly branched at the base, vegetative parts covered with 0.3–0.7 mm long white hairs. Stems 30 cm long, at the base c. 5 mm in diameter, bark pale brown to dark grey brown, branches of the current year 15–25 cm long, densely covered with subappressed 0.4–0.8 mm long white hairs. Internodes 5–19 mm long, greenish to dark greyish brown. Stipules whitish membranous, 5–9 mm long, ovate to broadly triangular, distinctly 2–3 nerved, obliquely inserted on the stem, sometimes embracing the stem but not fully amplexicaule, 1–3 mm adnate to the petiole, glabrous, margins ciliate. Leaves 2–5.5 cm long, paripinnate, patent to erect, petiole 1–1.5 cm long, rachis 1–4 cm long, persistent, pungent, sparsely to densely hairy, covered with ascending to spreading 0.3–0.8 mm long white hairs, glabrous with age, yellowish green, becoming pale brown with age, terminal spine up to 2 times longer than the terminal leaflets. Leaflets in 4–8 pairs, elliptic, lanceolate or oblanceolate, mostly folded, basal ones 3.5– 11× 1.5–3.8 mm, the upper ones distinctly smaller, acute, sometimes mucronate, adaxial surface glabrescent to sparsely pilose, abaxial surface covered with spreading to subappressed 0.5–0.8 mm long white hairs. Peduncles up to 0.5 cm long, densely hairy, covered with 0.3–0.5 mm long white hairs. Racemes subsessile, 1-3 flowered. Bracts whitish-membranous, 3–4 mm, filiform, glabrous or white and black ciliate. Bracteoles absent. Pedicels 1–2 mm long, densely covered with appressed black and spreading white hairs. Calyx 11.5–12.5 mm long, yellowish green, tubular, densely covered with appressed 0.2–0.3 mm long black hairs, mixed with few 0.3–1.5 mm long white hairs, glabrescent at fruiting and often nearly glabrous, shiny, teeth with a triangular base, subulate, 3–5 mm, sparsely pilose with white hairs. Petals yellow, dark red with age, sometimes cream white, becoming dark brown to purplish brown with age, glabrous. Standard 14–20 mm long, limb 4.5–8 mm wide, obovate, emarginate to obtuse, angularly passing into the rather short claw. Wings 17–18 mm long, limb narrowly oblong, obtuse, 7–7.5× 1–1.5 mm, auricles 0.8–1.3 mm long, claw 9–10 mm. Keel 15–18 mm, limb obliquely elliptic, with curved lower edge in the middle and straight to slightly curved upper edge, 5–7× 2.5–4 mm, auricle up to 1 mm long. Stamen-tube 15–17 mm long, obliquely cut at the mouth. Ovary shortly stipitate with a stipe ca. 1.5 mm long, densely covered with 0.5–1 mm long white hairs, style hairy at the base. Legumes ellipsoid, 14–16 mm long and 5–6 mm high, keeled ventrally, rounded with a thickened nerve dorsally, with a 1–2 mm long slightly curved beak, 4–8 seeded, completely bilocular; valves coriaceous, pale brown, sparsely to densely covered with 0.5–0.7 mm long spreading white hairs and 0.2–0.3 mm long subappressed black hairs. Seeds 2–3.5× 2–2.5 mm, pale brown to dark brown, often black-dotted, shiny, reniform to oblong.

Phenology. Flowers during July to August.

Specimens examined: Pakistan, B7 , Khyber Pakhtunkhwa province, Chitral district, Garam Chashma to Shah Saleem 36° 1’ 7.02” N, 71° 25’ 12.70” E, elev. 2,722 m a.s.l., 3 September, 2024, Amjad Khan & Amir Sultan, ( RAW 103288 ) ; near Shah Saleem 36° 4’ 51.14” N, 71° 20’ 19.97” E, elev. 3,267 m a.s.l., 3 September, 2024, Amjad Khan & Amir Sultan, ( RAW 103289 ) ; ca. 28 km from Garam Chashma on way to Shah Saleem , Alt. ± 3,000 m a.s.l., 12 August, 1992, Tahir Ali, S. Z, Husain & Gohar Khan, Col. No. 2295, ( KUH 57793 ) .

Specimens were carefully examined and we found that its characters exactly match the description of A. nigrocalyx Slobodov ex Grig. ( Podlech and Zarre 2013). Among the species of sect. Aegacantha , A. nigrocalyx is characterized by leaflets sparsely hairy towards the margins on the adaxial surface, calyx densely covered with appressed black hairs along with few longer white hairs mixed in, nearly glabrous with age, corolla yellow, dark red with age and standard 14–19 mm. In Pakistani Aegacantha species, A. nigrocalyx is the only one with very short legumes.

Figures

FIGURE 8. Astragalus nigrocalyx: (A–B) Habit, (C) Branch close-up, (D) Flowering, (E) Flowers close-up, (F) Fruiting. Photographs taken on 3 September, 2024, by A. Khan & A. Sultan.

FIGURE 9. Astragalus nigrocalyx: (A) Stipule, (B) Bract, (C) Calyx, (D) Standard, (E) Wings, (F–G) Keels, (H) Stamens, (I) Ovary, (J–K) Legumes, (L–M) Seeds.