Astragalus Pennellianus

  • Title

    Astragalus Pennellianus

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Astragalus pennellianus Barneby

  • Description

    22. Astragalus Pennellianus

    Slender perennial, with forked taproot and knotty root-crown at or just below soil-level, loosely strigulose-villosulous with fine, subappressed, spreading, and incumbent, partly sinuous hairs up to 0.4-0.7 (0.9) mm. long, the growing tips cinereous or canescent, the herbage greenish when mature, the leaflets glabrous above, densely pubescent along the prominent midrib beneath; stems weakly ascending or spreading, 6-40 cm. long, either simple or spurred at 1-2 nodes preceding the first peduncle, floriferous from 2-4 nodes upward from near or above the middle; stipules all fully amplexicaul and connate, but somewhat dimorphic, the lowermost 1-2.5 mm. long, papery, glabrous, united into a shortly bidentate sheath, the rest longer and narrower, herbaceous, up to 4-6.5 (7.5) mm. long, densely pubescent dorsally, the sheath cleft halfway into lanceolate, ascending free blades; leaves (2) 3-7.5 cm. long, all but the lowest subsessile, with slender rachis and (17) 25-41 (47) opposite or largely scattered, ovate, obovate, or broadly oblong-elliptic, widely and openly retuse, flat leaflets (1) 1.5-5 mm. long; peduncles slender, erect or divergent, 4.5-9 cm. long, equaling or shorter than the leaf, or the most vigorous ones surpassing it; racemes loosely (7) 10-25-flowered, the flowers declined in age, the axis ± elongating, (2) 3-4 cm. long in fruit; bracts submembranous, pallid or purplish, oblanceolate or lanceolate, 2-4 mm. long; pedicels at first ascending, 0.6-1.1 mm. long, in fruit either ascending or variably arched out- and downward, thickened, 1-2.1 mm. long; bracteoles 0; calyx 4.9-6 mm. long, villosulous with white, or fuscous and some longer white hairs, the scarcely oblique disc 0.8-0.9 mm. deep, the tube 2.9-3.8 mm. long, 2-2.7 mm. in diameter, the broadly lance-subulate teeth 1.7-2.5 mm. long, the whole becoming papery, marcescent unruptured; petals creamy-white or pale purple; banner gently recurved through ±40°, elliptic-obovate, openly notched, 8-9.3 mm. long, 4-5 mm. wide; wings as long or nearly so, 7.5-9.6 mm. long, the claws 3-3.7 mm., the elliptic- oblanceolate, obtuse or obscurely erose-emarginate, slightly incurved blades 5.5 6.5 mm. long, 1.8-2.2 mm. wide; keel 6.1-7 mm. long, the claws 3-3.5 mm., the half-obovate blades 3.3-3.9 mm. long, 2-2.3 mm. wide, abruptly incurved through 90-95° to the bluntly deltoid apex; anthers 0.4—0.6 mm. long; pod loosely pendulous, stipitate, the slender stipe 3.5-7 mm. long, the body narrowly oblong- or lance-elliptic in dorsiventral view, 1.6-2.8 cm. long, 4.5-6 mm. in diameter, straight or a trifle decurved, tapering downward into the stipe, cuneately contracted into the cuspidate apex, strongly obcompressed, obtusely carinate ventrally by the suture, widely and openly sulcate dorsally, the thin, green or often purplish, glabrous valves becoming papery, delicately cross-reticulate, inflexed as a complete or nearly complete septum ± 1 mm. wide; dehiscence unknown; ovules 10-14; seeds purplish-brown, smooth, ± 2-2.2 mm. long.—Collections: 3 (o); representative: Pennell 18,399 (NY); Waterfall 15,488 (NY).

    Open rocky woodland of oak, pine, and arbutus, 9300-10,300 feet, locally plentiful in the Sierra Madre Occidental in Durango.—Map No. 8.—July to September.

    Astragalus Pennellianus (Francis Whittier Pennell, 1886-1952, eminent student of Scrophulariaceae), sp. nov., inter Strigulosos legumine elongato anguste ellipsoideo donatos pube laxa hirsutula, foliolisque parvis valde numerosis (saepissime 25-41) insignis.—Caules graciles 6-40 cm. longi; racemi (7) 10-20 (25)-flori; flores parvuli vexillo 8-9.3 mm. longo, petalis ochroleucis vel lilacinis; legumen pendulum, anguste oblongo-ellipsoideum, praeter stipitem gracilem 3.5—7 mm. longum 1.6—2.8 cm. longum. obcompressum, dorso aperte sulcatum, subbiloculare, 10—14-ovulatum, glabrum.—Durango: e. slopes of Cerro Prieto, about 20 miles airline w. of Otinapa, July 10, 1950, James H. Maysilles 7354.—Holotypus, MICH! isotypi, NY, RSA!

    The slenderly oblong-ellipsoid, glabrous pod of the Pennell milk-vetch is similar to that of A. jaliscensis and A. zacatecanus in all respects except that the stipe is, on the average, longer and the ovules significantly fewer. The species resembles A. jaliscensis the more closely m number of flowers to the raceme, although the fruiting axis is shorter and the flowers themselves somewhat smaller. The plants are easily recognized otherwise by the loose, hirsutulous pubescence, and especially by the very numerous and small leaflets diminishing in size upward along the rachis. The flowers apparently vary in color, for Maysilles recorded the petals on the Cerro Prieto as "cream or white," whereas Pennell, who first discovered the species in 1934, at Metates, north of Cueva, close to the type-locality, found them "light violet-purple."