Astragalus scalaris S. Watson, Proc. Amer. Acad., 1888

Castillón, Eduardo Estrada, Quintanilla, José Ángel Villarreal, Delgado-Salinas, Alfonso & Rebman, Jon P., 2023, The genus Astragalus (Leguminosae: Papilionoideae: Galegeae) in Mexico, Phytotaxa 586 (1), pp. 1921-1935 : 1921-1935

88. Astragalus scalaris S. Watson, Proc. Amer. Acad. 23: 270.1888

Type:— MEXICO, Chihuahua, by streams in the Sierra Madre, Chihuahua, 23 September 1887, C. G. Pringle 1220 (holotype: not found; isotype: NY00005845!, NDG26915 digital image!, MIN1000374 digital image!, MEL2074448 digital image!, PH00005701digital image!, AC00319845 digital image!, MEXU01169236!, F0058948F digital image!, NA0026154 digital image!, NY00005843!, US00930817 digital image!, Phaca scalaris (S. Watson) Rydb., N. Amer. Fl. 24: 361. 1929. — Astragalus scalaris S. Watson var. quercetinus M. E. Jones, Rev. N. -Amer. Astragalus 107. 1923.

Perennial. Stems up to 55 cm long, commonly with single stem at base, when so, erect or branched near base or at half, sometimes several ones from base, striate, minute, the trichomes short, up to 0.4 mm long, straight to appressed. Stipules 1.5–5 mm long, triangular to lancoelate, semi-clasping, not connate, decurrent. Leaves 1.5–13 cm long, leaflets 11–31, 1.2–13 mm long, frequently with the pairs, distant from each other, linear, linear-elliptic, elliptic to ovate, notched apically, occasionally obtuse and mucronate, adaxially glabrate. Peduncles 2.4–11 cm long, erect to incurved; the racemes 3–21 cm long, lax, flowers 15–50, rarely less. Flowers pink-purple, whitish, sometimes with purple tones apically, turning pale to ochroleucous when drying; the calyx 2.2–2.9 × 1.7–2 mm, strigose, trichomes black, the tube short, 1.6–2 mm long, campanulate to somewhat almost hemispheric, basally inequilaterous to oblique, the teeth 0.5–1 mm long, triangular, one pair wider and shorter than the rest; the banner 5–6.4 × 3.6–4.8 mm, recurved, ovate, slightly notched apically; the wings 4.8–5.5 × 1.4–2.3 mm, the claw 1.6–1.9 mm long, the blade 3.6–4.4 mm long, oblong to oblanceolate, straight or almost so; the keel 3.7–4.7 × 1.7–2.1 mm, the claw 1.5–1.9 mm long, the blade 2.6–3 mm long, triangular to obovate, dorsally oblique. Pod 4–8 × 2.5–3.5 mm, deflexed or horizontal, stipitate (stipe 0.4–1.3 mm long), triquetrous, sometimes barely inflated-trigonous, oblique, obovoid, basally rounded or wide narrowed, distally abruptly contracted in a incurved short beak, ventrally straight carinate or slightly convex, dorsally shallowly and openly sulcate, the valves green, thin, papery and ochre with age, reticulate, septum absent, when present tiny but incomplete; ovules 4–9; seeds 2–2.5 mm long, mitten shaped, brown, smooth.

Distribution:— Endemic to Mexico, exclusively in Chihuahua, mountains of the western portion (Madera, Gómez Farías, and Guerrero municipalities), low hills in the central region (Chihuahua) and mountains in the southern part (San Francisco del Oro and Parral) ( Fig. 25 ).

Habitat:— Streams; areas with disturbance; oak-pine forest; pine forest; oak forest; 1950–2400 m.

Comments:— The range of A. scalaris includes another 13 species of Astragalus inhabiting the same ecosystems, but the morphological peculiarities of this species make it easily distinguishable from the rest, since it is the only species with small, widened, oblique to obovoid, triquetrous or inflated-trigonous, stipitate pods (4–8 mm long), peduncles 2–3 times longer than leaves, and lax racemes with abundant flowers that are well spearated from each other.

Specimens examined:—CHIHUAHUA: 23 September 1887, Por arroyos de la Sierra Madre, C. G. Pringle 1220 ( MEXU, NY) ; 16 September 1899, Chihuahua Recogido en la Sierra Madres cerca de Chhichupa, C. H. T. Townsend 443, C. M. McBaber ( NY, US) ; 30 September 1883, Sierra Madre C. G. Pringle 1587 ( NY) ; 30 September 1888, Sierra Madre, C. G. Pringle 1587 ( NY) ; 3 September 1994, Gómez Farías. Laguna de Babícora , E. Estrada 2929, T. Lebge, G. Quintana ( NY) ; 16 September 1899, Chihuahua Recogido en la Sierra Madres cerca de Chhichupa, C. H. T. Townsend 443, C. M. Barber ( MEXU, NY) ; 16–17 September 1934, Barranca Colorad ”, Sierra Gazachic 35, F. W. Pennel 18933 ( NY, US) ; 16 September 1903, San Diego Canyon , M. E Jones s.n. ( CAS, NY) ; 16 September 1899, Chihuahua Recogido en la Sierra Madres cerca de Chhichupa, C. H. Townsend, 433, M. Barber ( MEXU) .

Figures

FIGURE 25. Map showing the distribution of Astragalus sanguineus, A. scalaris, A. scutaneus, A. sinaloae, and A. spellenbergii in Mexico.