Astragalus chloodes

  • Title

    Astragalus chloodes

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus chloodes Barneby

  • Description

    68. Astragalus chloodes

    Low, tufted, with a multicipital caudex beset with remains of stipules and leaf- bases, silvery- or gray-strigulose nearly throughout with fine, appressed, straight and parallel hairs up to 0.55—0.75 mm. long; stems of the year reduced to crowns or nearly so; stipules scarious, pallid except for the prominent herbaceous midrib, 2—8 mm. long, those of the lowest leaves smallest, all amplexicaul and connate through over half to nearly their whole length into a loose, bidentate sheath, densely strigulose dorsally, at least when young; leaves all reduced to phyllodia, dimorphic, the lowest spreading, linear-oblanceolate, 1-4.5 (7) cm. long, gradually expanded upward into a ± involute blade up to 2.5 mm. wide, early withering- persistent, the later ones erect, stiff, narrowly linear, very acute and subspinulose at apex, (6) 10-17 cm. long, usually tightly inrolled, subterete but ventrally channeled, less than 1 mm. in diameter, occasionally with only the margins elevated and then up to 1.4 (2) mm. wide; peduncles scapose, erect, slender, wiry, (2) 4—9 cm. long, shorter than the longer leaves; racemes very loosely 7-23-flowered, the flowers ascending, the axis (4.5) 6—24 cm. long in fruit; bracts scarious, boat-shaped, ovate or lanceolate, mostly acute, 2—4.5 mm. long; pedicels erect or narrowly ascending, at anthesis slender, 1—2 mm., in fruit somewhat thickened, 1.5-2.5 mm. long, tardily, if at all, disjointing; bracteoles 0; calyx 4.5-6.7 mm. long, densely white-strigulose, the symmetric disc 0.4-0.8 mm. deep, the campanulate tube 2-3 mm. long, 1.8—2.3 mm. in diameter, becoming papery and strongly 5 -nerved in age, the narrowly subulate-aristiform, very acute, somewhat rigid, stellately spreading teeth 2.5—4 mm. long; petals pink-purple, the banner striate; banner sharply recurved through ± 90°, suborbicular-cuneate, notched, 6.2-8.2 mm. long, 5-7.4 mm. wide; wings 6.3-8 mm. long, the claws 2.3-2.9 mm., the oblong-elliptic, obtuse blades 4.3-5.6 mm. long, 1.6-2 (2.5) mm. wide, both incurved but the left one more so than the right and its inner margin infolded; keel 6-6.6 mm. long, the claws 2.4-3.2 mm., the blades 4-4.8 mm. long, 2.1-2.6 mm. wide, incurved through ± 100° to the triangular, subacute apex; anthers 0.4-0.5 mm. long; pod erect or narrowly ascending, tardily deciduous from the receptacle, obliquely lanceolate or oblong-elliptic in profile, a trifle incurved just above the base and straight thereafter, 8-12 mm. long, 1.7-3 mm. in diameter, rounded at base, tapering distally into the cuspidate apex, laterally compressed and two-sided, bicarinate by the sutures (the ventral one the thicker and more prominent), the faces low-convex, the thinly fleshy, green but often purple-speckled or minutely red-mottled, glabrous or strigulose valves becoming stramineous, stiffly papery, reticulate near the sutures but smooth toward the middle; ovules 4-8, commonly 6; seeds not seen—Collections: 7 (iii); representative: Graham 7718 (GH, US); W. A. Weber 5312 (CAS, SMU); Holmgren & Tillett 9530 (CAS, MO, NY, RSA); Barneby 12,713 (CAS, NY).

    Ledges and pockets of sandstone cliffs or outcrops, sometimes on talus slopes, 4800-5550 feet, forming colonies but very local, known only from about the mouth of the Green River gorge within and near Dinosaur National Monument, Uintah County, Utah.—Map No. 26.— May to early July.

    Astragalus chloodes (grasslike, of the phyllodia) Barneby in Leafl. West. Bot. 5: 6. 1947.—"Utah: ... 6 miles southeast of Jensen, Uintah Co....7 June 1946 ... Ripley & Barneby No. 7797"—Holotypus, CAS! isotypi, GH, K, NY, POM, RM, RSA, UTC!

    Because of the singular modification of the principal leaves into stiff and narrow, usually involute and sharp-pointed phyllodes, which resemble the blades of some xerophytic grasses, it would be difficult to recognize a member of the Bean Family in sterile plants of the grass milk-vetch. The flowers and pods, however, are quite similar to those of A. spatulatus, of which A. chloodes might be described in loose terms as a drawn-out or etiolated version. Apart from the greater length of the phyllodes and the much looser, longer, more numerously flowered racemes, the species is remarkable for its prominently 5-nerved fruiting calyx and the subulate-aristiform, stellately spreading calyx-teeth.

    The grass milk-vetch is closely and obligately associated with the white sandstone of the Navajo Series which forms the portals of Split Canyon, where the Green River issues from its passage through the Uinta Mountains out onto the Basin floor. Of the seven collections examined, four are from near the headquarters of Dinosaur Monument, two from the type- station southeast of Jensen, and one from Brush Creek at a point about thirteen miles northeast of Vernal. The known range of the species is about fifteen miles in diameter. The plants occur on ledges of vertical cliffs, on talus, and along seams of domed or shelving wind-sculptured rocks, where they form large, spiky tufts anchored by a stout, woody, deeply penetrating taproot.

    According to Graham (1937, p. 249, as A. moencoppensis), A. chloodes was first discovered in 1912 by O. A. Peterson, member of a Carnegie Museum paleontological field party.