Monographs Details: Astragalus didymocarpus var. obispensis (Rydb.) Barneby
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:

360d. Astragalus didymocarpus var. obispensis

Herbage greenish-cinereous or subcanescent, the leaflets glabrous or medially glabrescent above; stems (1) 3-several, ascending or diffuse, (2.5) 3-25 cm. long, commonly rather robust, sometimes quite slender; leaves 1-5.5 cm. long, with 917 leaflets 1.5-10 mm. long; racemes (5) 8-30-flowered, the heads 8-13 mm. in diameter at full anthesis, the axis 2-20 mm. long in fruit; calyx 3.2-5.1 mm. long, densely villosulous with largely white or with mixed black and white hairs up to 0.7-1 mm. long, the tube 2.1-2.8 mm. long, (1.5) 1.7-2.1 mm. in diameter, the subulate-setaceous teeth (0.9) 1.1-2.5 mm. long; banner obovate-cuneate, (6.2) 7-8.6 mm. long, 2.5-5 mm. wide; wings (5.2) 5.8-7.1 mm. long, the claws 2.22.9 mm., the blades (3.2) 3.6-5 mm. long, 1.1-1.7 mm. wide; keel (5.2) 5.5-12 mm. long, the claws 2.4-3.2 mm., the lunately half-elliptic blades 2.9-4.2 mm. long, 1.2-1.8 mm. wide, incurved through 55-90° to the narrowly triangular, slightly porrect, acute or subacute apex; anthers (0.2) 0.25-0.4 mm. long; pod as in var. didymocarpus, sparsely hispidulous throughout or distally.—Collections: 18 (i); representative: C. B. Wolf 6301 (CAS, TEX, WS); Munz 5096 (POM, UC); Jepson 13,745 (UC); Eastwood 2601 (CAS, NY), 9395 (CAS); Orcutt 1129 (NY); Wiggins 9890 (DS).

Dry grassy hills, valley floors, openings in chaparral, 1400-3100 feet, locally plentiful in scattered stations in the interior cismontane valleys of southern California, extending just to the desert edge, from Antelope Valley, Los Angeles County, south to northern Baja California near Laguna Hansen and the Valley of Palms, apparently extending west to the Pacific Coast at Ensenada, but here and in the San Diego region (at lower elevations) atypical and intergradient to var. didymocarpus; apparently isolated, at 3500 feet, near the south end of Sierra San Pedro Martir, Baja California.—Map No. 160.—March to May.

Astragalus didymocarpus var. obispensis (Rydb.) Jeps., Fl. Calif. 2: 376. 1936 ("obispoensis"), based on Hesperastragalus obispensis (of San Luis Obispo, an error in the original data) Rydb. in Bull. Torr. Club 53: 167. 1926.—"The type was collected at San Luis Obispo, California, May 6, 1882, Jones 3229 (in part, N. Y. Bot. Gard.). The sheet contains 3 specimens ... The lower two specimens belong to this species ... "—Holotypus, the two plants indicated by Rydberg, NY!—The label (Barneby 1950, p. 213) doubtless belongs with the third specimen, representing A. Gambelianus, as do duplicates at NY, POM (3 sheets), WS, the obispensis element probably introduced inadvertently.—A. dispermus var. obispensis (Rydb.) Tidest. in Proc. Biol. Soc. Wash. 50: 21. 1937.

The unfortunately named var. obispensis can be described as a large-flowered form of var. dispermus, which it resembles in its usually white- (but not infrequently partly black-) villous calyx and habit of growth. All authors (Rydberg, 1926; Jepson, 1936; James, 1951) who have listed exsiccata of var. dispermus have included one or more examples of var. obispensis, which differs sufficiently in its thicker spikes of larger, often relatively highly colored and even showy flowers, and especially in its much longer keel with porrectly triangular tip. Rydberg’s description of the pod as glabrous is contradicted by study of the typus; no specimen with a really hairless pod has been seen. The variety is particularly well marked in its main range just west of the deserts in cismontane California, where it seems to be adapted to the arid grasslands transitional to desert conditions. The material examined from interior Baja California has for the most part slightly smaller flowers with characteristic keel-tip; but several ambiguous collections from near the coast between San Diego and Ensenada suggest passage between var. obispensis and var. didymocarpus in all critical characters.