Astragalus striatiflorus

Shortly caulescent, loosely tufted, densely and canescently hirsutulous throughout with spreading and ascending hairs up to 0.6—0.9 mm. long; stems few, arising from a buried root-crown or caudex, 1—5 cm. long, only the tips emerging from the sand, the longest distal internodes not over 1 cm. long; stipules 2-4

mm. long, broadly ovate or ovate-acuminate, papery-scarious or early becoming so, prominently several-nerved, fully amplexicaul and united both behind and opposite the petiole into a loose, cuplike sheath; leaves (1) 1.5-4 cm. long, with slender petiole and (5) 7-13 crowded or subcontiguous, ovate, obovate, or broadly oblanceolate, obtuse, mucronulate, or obscurely emarginate, loosely folded and dorsally keeled leaflets 2—7 mm. long, the petioles often subpersistent on the caudex-branches; peduncles slender, ascending, 1—3 cm. long, reclinate in fruit, racemes loosely but very shortly 2—5-flowered, the flowers spreading, the axis little elongating, 2-10 mm. long in fruit; bracts membranous, ovate or broadly lanceolate, 1.5-2.5 mm. long; pedicels at anthesis 1-1.5 mm., in fruit spreading and up to 2.5 mm. long; bracteoles 0; calyx 5.5—7 mm. long, hirsutulous with dark or mixed pale and dark hairs, the subsymmetric disc 0.5—0.8 mm. deep, the campanulate tube 3-4 mm. long, 2.8-3.4 mm. in diameter, the subulate teeth 1.8-3 mm. long, the whole becoming papery, ruptured, marcescent; petals whitish commonly suffused with lilac, the banner purple-veined, the keel prominently purple-tipped; banner recurved through 45°, 9.5—12 mm. long, the short, cuneate claw abruptly expanded into a suborbicular, subentire blade 8—10 mm. wide; wings 8.9—11 mm. long, the claws 3.1-4 mm., the broadly oblanceolate, subtruncate blades 6.2-7.4 mm. long, 2.6—3.5 mm. wide; keel 9—11 mm. long, the claws 2.7—4 mm., the lunately lanceolate blades 6.2—7.6 mm. long, 2.5—3 mm. broad, gently incurved through ± 45° to the narrow, acuminate, beaklike but finally obtuse apex; anthers 0.55-0.9 mm. long; pod spreading (humistrate), sessile, broadly ellipsoid or subglobose, bladdery-inflated, 1.2—1.5 (1.8) cm. long, 8—13 (or when pressed apparently up to 15) mm. in diameter, terete but shallowly and openly sulcate along both sutures, shortly apiculate-beaked, the thin, brightly mottled valves becoming papery, hirsutulous with white, shining hairs up to 0.7—1.5 mm. long, inflexed as a complete septum; seeds olivaceous turning dark brown, smooth, ± 2.2 mm. long.—Collections: 5 (iii); representative: Ripley & Barneby 4358 (CAS, NY, RSA), 4365 (CAS, RSA), 4815 (CAS, K, RSA).

Ledges and mobile, dunelike detritus at the foot of sandstone cliffs, the plants commonly buried, except for the growing tips, in shifting sand, 5600-6100 feet, very local but forming colonies, known only from the south-facing Zion Escarpment, between the Virgin and Paria Rivers, Washington and Kane Counties, Utah. —Map No. 96.—May and June.

Astragalus striatiflorus (with lined, or purple-veined flowers) Jones in Proc. Calif. Acad. Sci. II, 7: 643. 1895.—"No. 6080k. September 25, 1894, above Springdale, Utah, 4000° alt., in red sand."—Holotypus, collected by M. E. Jones, an autumnal fragment now lacking flower or fruit, POM!

The singular but delightful little escarpment milk-vetch, A. striatiflorus, was described by Jones from a fragmentary but fortunately still identifiable specimen by chance in flower late in September and lacking the characteristic fruit. In absence of further collections Jones lost faith in the proposition and finally (1923, Index) listed the name as a synonym of A. Sileranus (= A. subcinereus), a much taller species of the same region differing in its unilocular, emmenoloboid pod. It was unknown to Rydberg (1929, p. 455). In describing sect. Cystiella I have already emphasized the unique combination of morphological characters by which A. striatiflorus is set off from all other North American Astragali, and I am still doubtful of its near affinities. It is introduced at this place because it agrees most closely in the position of the root-crown, the connate stipules, and the deciduous, septiferous fruit of thin texture with sect. Monoenses, although still distinguished by its beaklike keel-tip and peculiar exserted style. The monotype A. circumdatus, which follows next in order, is perhaps more nearly related. This has many features, including a beaked keel, in common with A. striatiflorus, but the pod is not inflated and of fleshy, ultimately leathery texture.

A pretty little plant, A. striatiflorus is easily recognized by its cryptophytic growth-habit, with all but the growing tips of the stems concealed by drifting sand, by its short racemes of rather small but proportionately ample, lilac-penciled flowers, and finally by the greatly swollen, papery, handsomely mottled and hirsutulous pod divided by a broad double septum into two chambers. In Johnson Canyon east of Kanab and near Zion Junction, the escarpment milk- vetch is confined to a narrow belt of steeply hummocked dunes lying close under the towering perpendicular cliffs, where it is associated at times with A. ceramicus and A. zionis. The known range of the species extends from Zion Canyon east to Johnson’s, a crow’s flight along the escarpment of some thirty or thirty-five miles.