Monographs Details: Astragalus rattanii A.Gray
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
Family:Fabaceae
Discussion:

329.  Astragalus Rattani

Variable in stature but usually quite slender, thinly strigulose with fine, straight, appressed or narrowly ascending hairs (distally often partly black or fuscous) up to 0.2—0.45 mm. long, the herbage green, the leaflets glabrous above; stems solitary and erect or 2—3 from the lowest nodes, the lateral ones sometimes again forking, either incurved-ascending or decumbent with ascending tips, the main axes (2.5) 4—30 cm. long, floriferous upward from near or well below the middle; stipules (1) 1.2—4 mm. long, submembranous, pallid, greenish, or purplish, becoming papery in age, triangular, ovate- or deltoid-acuminate, glabrous or nearly so dorsally, black- or white-ciliate, the blades commonly squarrose; leaves (1.5) 2—5 cm. long, slender-petioled but the uppermost ones shortly so, with (5) 7—11 (13) broadly obovate or obovate-cuneate, more rarely (especially in some upper, but sometimes in all leaves) oblanceolate or (in some early leaves) sub- orbicular-obcordate, emarginate or retuse, flat or loosely folded leaflets 2-12 mm. long, peduncles erect, (1.5) 2—7 cm. long, mostly as long or longer than the leaf, racemes very shortly or subumbellately 2—10-flowered, the flowers spreading, the axis not elongating, 1—4 (5) mm. long in fruit; bracts membranous, ovate or triangular-acuminate, 0.5—0.8 mm. long; pedicels ascending, straight, at anthesis 0.3—0.7 mm., in fruit thickened and 0.5—1.3 mm. long; bracteoles 0.2, minute when present, calyx 2.5—5 mm. long, rather densely strigulose with black or commonly mixed black and white hairs, the subulate teeth about ?-½ as long as the campanulate tube, the whole becoming papery, marcescent unruptured; petals pink- purple with paler wing-tips and pale, striate eye in the banner-blade, or sometimes only the distal third of the banner and the keel-tip purple, exceptionally white throughout; banner recurved through ± 40°, broadly elliptic-oblanceolate or ovate- cuneate, subtruncate or notched at apex, 7.2-12 mm. long; wings shorter, the blades oblong-oblanceolate, obliquely truncate or subemarginate, straight or a trifle incurved distally; keel 3.8—8.1 mm. long, the half-obovate blades incurved through 90-100° to the broadly rounded or deltoid, often obscurely porrect apex; anthers 0.3—0.55 mm. long; pod ascending at a narrow or a wide angle, sessile on the slightly elevated receptacle, very narrowly linear-acuminate in profile, (1.5) 1.8-5 (5.7) cm. long, 1.7-2.7 (3.1) mm. in diameter, either gently incurved or straight, cuneate or cuneately tapering (and then sometimes pseudostipitate) at base, gradually tapering upward into a stout, straight, subulate beak 3—7 mm. long, obscurely trigonous when young, subterete in age, low-carinate by the scarcely elevated ventral suture, shallowly sulcate dorsally (the groove sometimes closed), the thinly fleshy, green or purple-tinged, finely strigulose valves becoming papery, brownish-stramineous, delicately reticulate, inflexed as a complete or semicomplete septum 0.6—1.6 mm. wide; ovules 8-20; seeds narrowly oblong, brown, sometimes purple-dotted, pitted or wrinkled or both, scarcely lustrous, 2.1-3.2 mm. long.

The Rattan milk-vetch, variable in flower-size and pod-length, has broken up into two races, a more vigorous var. Rattani of the outer North Coast Range and a more slender one of the inner Coast Range and foothills bordering the lower Sacramento Valley. In either phase A. Rattani is distinguished from A. tener by its longer, often needle-like pod cuneately tapering rather than rounded at base, and by the same characters and the subumbellate fruiting raceme from A. pauperculus.