Monographs Details: Astragalus nuttallianus DC. var. nuttallianus
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:

333a. Astragalus Nuttallianus var. Nuttallianus

Thinly strigulose with fine, appressed or subappressed hairs up to 0.4—0.65 (0.7) mm. long, the herbage dark green, the leaflets glabrous above; stems (0.2) 0.5-3 (4) dm. long; leaves 2-6 (7.5) cm. long, with (7) 11-19 (23) linear- oblong, oblong, oblong-cuneate, or ovate-cuneate, retuse or truncate-emarginate, or in some lower leaves obcordate leaflets (2) 4-14 (17) mm. long; peduncles 2-7 (8.5) cm. long; racemes subcapitately (1) 2-6 (7)-flowered, the axis not or scarcely elongating, not over 8 (10) mm. long in fruit; calyx (3.5) 3.7-5.4 mm. long, thinly strigulose with black, mixed, or white hairs, the pallid or sometimes purplish tube 1.3-2.4 mm. long, 1.3-1.8 mm. in diameter, the lanceolate or Unear-lanceolate, herbaceous teeth (1.7) 1.9—3.2 mm. long; petals reddish- or amethystine-purple with a pale, striate eye in the banner, drying violet; banner (4.3) 4.8-7.3 mm. long, (2.6) 3.4—5.5 mm. wide; wings 4.7—6.7 mm. long; keel (3.8) 4.3-5.8 mm. long, the claws (1.4) 1.7-2.2 (2.4) mm. the lunately half-elliptic blades 2.5-3.6 (3.9) mm. long, 1.3-2.2 mm. wide, incurved through 80—95° to the acutely triangular or sharply deltoid, erect or porrect apex; pod declined, deflexed, or spreading and incurved-ascending, sessile, (1.2) 1.6-2.6 cm. long, (2) 2.4—3.5 mm. in diameter, nearly straight or gently incurved, but if curved usually only in the lower fourth and nearly straight thereafter, at first compressed-triquetrous but often becoming tetragonous when fully ripe, the valves glabrous, the septum complete, 1.3-2 mm. wide; ovules 10-16.—Collections: 147 (xi); representative: A. & R. Nelson 1016 (SMU, TEX); Bush 1019 (ND, NY); Cory 55,695 (SMU, WS); Ruth 12 (NY, SMU, WIS); Shinners 9265 (OKLA, SMU), 10,972, 14,218, 18,547 (SMU); Ripley & Barneby 4123, 11,057, 11,066 (CAS, RSA).

Prairies, stony or sandy pastures, roadsides, and open pine or oak woods, mostly below 2000 feet, in various types of light and heavy soils, perhaps most abundant on limestones, widespread and locally very common from northeastern and northcentral Oklahoma and western Arkansas south to southern Texas (Duval, Jim Wells, and San Patricio Counties), west in Oklahoma to the south west corner of the state and in Texas to Nolan County and the Edwards Plateau in Sutton and Uvalde Counties, east in Texas almost to the Sabine River, but rare and scattered on the Coastal Plain.—Map No. 149.—March to June.

Astragalus Nuttallianus (Thomas Nuttall, 1786-1859) A. DC., Prod. 2: 289. 1825, a substitute for A. micranthus (small-flowered) Nutt. in Jour. Acad. Philad. 2: 122. 1821 (non Desv., 1814).—"On the plains of Red River," and cultivated in the garden of the University of Pennsylvania.—Holotypus, labeled by Nuttall "Astragalus * Nuttallianus. Red River.,"PH! isotypi, G, K, and labeled "Arkansa, Nuttall.," BM, K, NY!—Tragacantha micrantha (Nutt.) O. Kze., Rev. Gen. 941. 1891. Hamosa Nuttalliana (A. DC.) Rydb. ap. Small, Fl. S.E. U. S. 1332. 1903.

Astragalus Nuttallianus var. enneajugus (with eleven pairs of leaflets) Jones, Contrib. West. Bot. 8: 22. 1898.—"Prairies of the Brazos, Tex., March 1844, Lindheimer... "—Cotypi, MO Nos. 17,072, 17,073, MO!

Astragalus Nuttallianus var. quadrilateralis (four-sided, of the pod) Jones, Contrib. West. Bot. 8: 22. 1898.—"Northwestern Arkansas from Canehill to Fort Gibson, on damp prairies, June 1835, Engelmann ... Indian Territory, Butler 1875 ... "—Lectotypus, Engelmann s. num., MO No. 17,074, MO!

The typical variety of small-flowered milk-vetch, var. Nuttallianus, is easily recognized by its consistently retuse or at least truncate-emarginate leaflets of a dark green color, by the calyx with its short, pale or purplish tube and long, slender, green teeth sometimes nearly as long as the banner, and by the glabrous pod commonly curved at base and straight thereafter but sometimes straight throughout. Apart from trivial variations in stature and orientation of the stems, it is perhaps the most constant and best characterized phase of the species. The pod varies in direction according to the attitude of the stems, being declined or deflexed from erect peduncles and spreading or incurved-ascending from procumbent branches. In Texas it is associated in places with var. trichocarpus, distinguished by pubescent pod, and var. pleianthus, differing in leaflet-shape and slightly larger flowers, and also with A. leptocarpus which it resembles closely in many ways, although easily separated by its much smaller flower and shorter pod containing 5-8 and not (9) 10-13 pairs of ovules or seeds.

As already pointed out by Rydberg (1927, p. 325), the epithet Nuttallianus was misapplied by Jones (1923, p. 270) to a complex of western forms corresponding with our vars. imperfectus, micranthiformis and austrinus, and the substance of the variety treated as vars. enneajugas and quadrilateralis. Both of these varieties were based on characteristic examples of var. Nuttallianus, the typus of var. enneajugas being a rather robust specimen in flower, that of var. quadrilateralis a specimen bearing ripe fruits which had become, as happens normally, distended by pressure of the expanding seeds and bluntly tetragonal.

The variety has been reported from Arkansas since early times, but I have no exact record of locality. Nuttall’s plant at New York is labeled simply "Arkansa," and the one at Philadelphia "Red River"; they may have originated in the southwest corner of the state. The type- locality of var. quadrilateralis was given as being in Arkansas, but Canehill lies only a few miles east of the Oklahoma line (in western Washington County) and Fort Gibson some forty miles west of it, on the Arkansas River. Likewise Fort Towson, although in Arkansas Territory when visited by Leavenworth, is situated in present-day Oklahoma (Choctaw County) and not in Arkansas as said by Rydberg (1927, l.c.).