Astragalus lentiginosus var. yuccanus

Robust winter-annual or short-lived perennial, commonly flowering the first year, strigulose or villosulous, or both, with straight and subappressed, straight and ascending, or largely sinuous, spreading and ascending hairs, the stems often canescent at and near the lowest nodes, sometimes also distally when young, the herbage green or greenish-cinereous, the leaflets bicolored, paler or yellowish- green and glabrous above; stems (in seedlings solitary) several or many, commonly stout and hollow, erect and ascending in clumps, 1.5—4 dm. long, simple or spurred (branched) at 1—5 nodes preceding the first peduncle; leaves (5) 7-16 cm. long, the upper ones mostly subsessile, with 13-21 (25) broadly elliptic, oval, rhombic-obovate, or obovate, retuse or emarginate, flat or loosely folded leaflets (4) 6-21 mm. long; peduncles (3) 5-10 cm. long; racemes loosely (12) 15—32- flowered, the axis early elongating, (4.5) 6-14 cm. long in fruit; calyx 6-7.5 mm. long, strigulose or villosulous with white or partly black hairs, the deeply campanulate or subcylindric tube 4.4-5.7 mm. long, 2.6-3.1 mm. in diameter, the teeth (1.3) 1.5—2.4 mm. long; petals white or ochroleucous and concolorous, or the keel-tip, and sometimes the banner, faintly lilac-tinged; banner broadly rhombic-obovate-cuneate, 11—15.6 mm. long, 6.2—9 mm. wide; wings as long or up to 2 mm. shorter, 11-13.5 mm. long, the claws 4.8-6 mm., the blades 7.1-9.1 mm. long, 1.9—2.8 mm. wide; keel 0.1—1.2 mm. shorter than the wings, the claws 4.5-6.3 mm., the prominent blades 6.4-7.6 mm. long, 2.8-3.3 mm. wide; pod plumply ovoid-acuminate or subglobose, strongly inflated, 1.5-2.2 (2.5) cm. long, 1—1.8 cm. in diameter, the deltoid or triangular-acuminate, more or less incurved beak unilocular and 3—7 mm. long, the pale green, glabrous or rarely strigulose valves becoming papery-membranous, stramineous, lustrous, subdiaphanous, the complete septum 4—7 mm. wide; ovules 17—26.—Collections: 16 (iii); representative: Palmer 589 (F, NY); Harrison & Kearney 7613 (F, NY, SAC); Eastwood 18,000, 18,370 (CAS); Ripley & Barneby 4261 (CAS, RSA).

Open sandy plains, sandy or rocky washes, and gulches in the foothills of desert mountains, with Larrea and in yucca-grassland, 1700-3300 feet, common and locally plentiful in parts of Mohave, western Yavapai, and Maricopa Counties, Arizona, south (perhaps disjunctly) to southern Pima County.—Map No. 131.— February to May.

Astragalus lentiginosus var. yuccanus (of Yucca, Arizona) Jones, Contrib. West. Bot. 8: 3. 1898 ("Yuccanus").—"Collected by the writer at Yucca Ariz., 1884."—Holotypus (Jones 3886), collected May 13, 1884, POM!—Isotypi, F, GH, NY, OB, US, UTC!—Cystium yuccanum (Jones) Rydb. in N. Amer. Fl. 24 : 407. 1929. A. yuccanus (Jones) Tidest. in Proc. Biol. Soc. Wash. 48: 40. 1935. A. Fremontii var. yuccanus (Jones) Tidest. in Tidest. & Kitt., Fl. Ariz. & New Mex. 216. 1941.

It is pointed out above that in the material referred to var. australis a gradual transition can be traced from the group of varieties typified by var. diphysus, and characterized by a perennial root, diffuse stems, and compact racemes of rather stiff-walled pods, into a largei assemblage of desert-dwelling forms. These plants are of more rapid growth and shorter duration, with stems ordinarily erect and ascending in clumps, and open racemes of usually papery or papery-membranous fruits. Of this second group var. yuccanus is the first to merit description, since it is geographically and morphologically nearest to var. australis, and apparently passes into it by a continuous series of variants. The variety is typically developed on the vast terraces by means of which the topography of western Arizona slopes off from the limestone- capped Peach Springs plateau toward the lower Colorado River. In this area it is extremely common, sometimes the most abundant herbaceous species over hundreds of acres, and assumes a strong individuality by virtue of its poorly graduated, white or often distinctly yellowish petals with relatively large and prominent keel as often as not faintly lilac-tinged at tip.