Astragalus drabelleformis

  • Title

    Astragalus drabelleformis

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus drabelliformis Barneby

  • Description

    69. Astragalus drabelleformis

    Dwarf or diminutive, matted or low-pulvinate, with a taproot and repeatedly forking, suffruticulose caudex beset with a thatch of marcescent leaf-bases impacted with sand or clay, densely strigose-strigulose with appressed (and sometimes a few subappressed) hairs up to (0.5) 0.6-1.5 mm. long, the herbage silvery-canescent, the phyllodia equally pubescent on both sides; stipules membranous, pallid, 1.5-5 mm. long, all fully amplexicaul and connate into a bidentate sheath, the shorter outer ones of the year’s cycle pubescent dorsally, the inner longer ones glabrous dorsally or nearly so, ciliate distally; leaves dimorphic, the lower ones oblanceolate or spatulate, mostly less than 1 cm. long, the later ones linear-oblanceolate, acute or subacute, 1-2.5 cm. long; peduncles subfiliform, ascending at anthesis, prostrate in fruit, 1-2.5 cm. long, much shorter to a little longer than the longest phyllodia; racemes loosely but very shortly 1-4-flowered, the axis in fruit 0-5 mm long, prolonged as a filiform appendage beyond the last flower; bracts submembranous, subulate, 0.6—1 mm. long; pedicels ascending, at anthesis 0.6-1 mm., in fruit scarcely thickened, 0.6-1.2 (2) mm. long; bracteoles 0; calyx strigulose with white or mixed black and white hairs, 2.5-3.3 mm. long, the subsym- metric disc 0.4-0.6 mm. deep, the campanulate or turbinately campanulate tube 1.7-2.1 mm. long, (1.2) 1.4-1.7 mm. in diameter, the subulate teeth 0.8-1.2 mm. long, the whole becoming papery, ruptured, marcescent; petals pink-purple, drying bluish, the banner with a pale eye; banner recurved through 50-70°, ovate-cuneate to spatulate-obovate, shallowly notched, 5.2-7 mm. long, 3.6-5.8 mm. wide; wings 4.8-6.3 mm. long, the claws 1.8-2.1 mm., the elliptic-oblanceolate, obtuse, slightly incurved blades 3.6-4.8 mm. long, 1.2-1.8 mm. wide; keel 3.7-4.3 mm. long, the claws 1.7-2.2 mm., the half-obovate blades 2.1-2.7 mm. long, 1.4-1.7 mm. wide, abruptly incurved through 100-120° to the bluntly deltoid apex; anthers (0.25) 0.3-0.4 mm. long; pod ascending (commonly humistrate), sessile, tardily deciduous, narrowly and obliquely lance-ellipsoid, slightly incurved, 5.5-8.5 mm. long, 1.8-2.5 mm. in diameter, broadly cuneate or rounded at base, contracted at apex into a subulate cusp ± 0.5 mm. long, the body obcompressed-triquetrous, carinate ventrally by the salient suture, openly sulcate dorsally through the lower, the lateral angles rounded, the green or sometimes red-mottled, scarcely fleshy valves becoming stramineous, papery, not inflexed, rather densely strigulose with short, straight hairs; dehiscence and seeds unknown; ovules 7-11.—Collections: 3 (iii); representative: Barneby 13,206 (NY, RSA).

    Summits and gullied slopes of low sandy or stony clay bluffs, 6900-7150 feet, forming colonies in open spaces among dwarf sagebrush, locally plentiful but known only from the upper Green River Valley between Big Piney and Daniel, Sublette County, Wyoming.—Map No. 27.—Late May to early July.

    Astragalus drabelliformis (with habit of sect. Drabellae, but an anomalous pod), sp. nov., cum A. spatulati Sheld. formis depressis vel pulvinatis habitu toto, foliorum florumque forma subexacte congruens, sed legumine obtuse trigono dorso aperte sed profunde sulcato nec (more Homalobi) de latere compresso suturis bicarinato valde diversa. Habitus Homalobi cum legumine Batidophacae in eadem specie genera ista arte et contra naturam circumscripta esse evincet!—Herba acaulescens densissime caespitosa vel pulvinafa, pilis mediofixis appressis incana; folia omnia in phyllodia reducta, ima brevia spatulata, superiora lineari-oblanceolata ad 2.5 cm. usque longa, stipulis membranaceis pallidis ocreantibus suffulta; racemi 1—4-flori, scapo filiformi foliis multo breviori vel subaequilongo; calycis 2.5-3.3 mm. longi dentes subu- lati ± 1 mm. longi; petala purpurea iis A. spatulati Sheld. simillima, vexillo 5.2-7 mm., carina 3.7—4.3 mm. longa; legumen adscendens sessile lanceolato-ellipsoideum 5.5—8.5 mm. longum 1.8—2.5 mm. diametro, leviter incurvum, triquetrim compressum, sutura ventrali prominula carinatum, dorso aperte sed profundiuscule sulcatum, angulis lateralibus obtusis, sectione transversali obcordata, valvulis chartaceis strigulosis viridibus nunc maculatis haud inflexis.— Wyoming: 8 miles north of Big Piney, Sublette County, June 13, 1961, Barneby 13,200.— Holotypus, CAS! isotypi, GH, NY, RM, RSA, US!—Also 11 miles south of Daniel, Sublette County, June 13, 1961, Barneby 13,202.—Paratypi, BRY, CAS, NY, RM, RSA, US!

    The bastard draba milk-vetch, A. drabelliformis, closely resembles the low tufted or mounded forms of A. spatulatus found in southern Wyoming and northern Utah (the so-called var. uniflorus, ox A. simplex). The two species are essentially identical in habit of growth, in foliage and stipules, and in fine detail of the calyx and petals, and no means of distinguishing the two at anthesis is apparent. The pods, however, are remarkably different. The fruit of A. spatulatus is of the common homaloboid type, flattened laterally and keeled by both sutures, whereas that of A. drabelliformis is bluntly trigonous, carinate only by the ventral suture, and grooved dorsally nearly its whole length. The pod of the new species resembles that of several caulescent astragali with connate stipules and pinnate foliage referred by Rydberg to Batidophaca, a genus designed to accommodate species with shortly bell-shaped calyx and unilocular pods intermediate in mode of compression between Homalobus, Phaca (sensu Rydberg) name Batidophaca was derived from the Greek batis, a skate, combined with the generic epithet Phaca, implying that the normally fish-shaped (laterally compressed) fruit of Homalobus had become dorsiventrally flattened after the fashion of the flat fishes such as sole or flounder. This modification has doubtless occurred independently several times in Astragalus, and very likely has been effected in both directions. The majority of homaloboid pods in North America seem to have been derived from a primitive terete type, but here a trigonous compression has arisen from the homaloboid one. Only a deeply prejudiced observer could suggest that A. drabelliformis, on account of its trigonous pod alone, is more closely related to some Batidophaca, such as A. humistratus, than to the Drabellae of which it has all other characters intact. It should be mentioned in this connection that the pod of A. simplicifolius, a close relative of both A. spatulatus and A. drabelliformis, exhibits a somewhat intermediate stage of modification. Both sutures remain salient, but the middle of the valves is dilated sideways, yielding a rhombic rather than narrowly elliptic and typically homaloboid section. Since the dorsal suture in A. drabelliformis is recessive, the section is inversely cordate.