Monographs Details: Astragalus lentiginosus var. australis Barneby
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
Description:Variety Description - Coarse perennial of short duration, strigulose-villosulous with largely straight and appressed or largely sinuous and ascending or spreading hairs up to 0.4-1.2 mm. long, the herbage green or greenish-cinereous, the leaflets glabrous above and sometimes so beneath; stems several or numerous, decumbent and ascending in low clumps, 2.5—4 dm. long, simple or branched at base, commonly robust and hollow below the middle, stramineous and striate in age; leaves (5) 6-17 cm. long, with (13) 15-21 (23) obovate, broadly elliptic, rhombic-ovate, or rarely suborbicular, emarginate or retuse, flat or loosely folded leaflets (4) 6-25 mm. long; peduncles usually stout, 3-7 (9) cm. long; racemes loosely (10) 15-33-flowered, the axis (3.5) 4-12 cm. long in fruit; calyx (5.3) 6.4-10.8 mm., the tube (4.5) 4.8—7 mm. long, 2.5-3.6 mm. in diameter, the teeth (0.8) 1.6-3.8 mm. long; petals pink-purple, sometimes pale, the color fugacious in drying; banner (13.2) 14.5-18 mm. long, 7.2-9.8 mm. wide; wings (12.1) 14.216.2 mm., the claws (5) 5.5-7 mm., the blades (8.1) 8.5-11 mm. long; keel 1 mm. shorter, as long, or rarely 0.5 mm. longer than the wings, (11.5) 13.2—16.2 mm., the claws (5) 5.7—7.5 mm., the blades 7—10 mm. long, 3—3.8 mm. wide; pod narrowly to broadly ovate-acuminate or broadly lance-acuminate in profile, slightly or greatly inflated, 1.2-2.2 cm. long, (4) 5-13 (15) mm. in diameter, usually strongly incurved, contracted distally into a deltoid or triangular- acuminate, distally unilocular beak about 4—8 mm. long, the thinly papery, green or faintly mottled, glabrous or rarely thinly pubescent valves turning stramineous or purplish, the complete septum about 1.7—5.5 mm., the funicular flange 0.5—1.1 mm. wide; ovules 1S—22.
Distribution and Ecology - Open desert, sandy playas and outwash fans, plains, and washes in the foothills of desert mountains, 2200—4250 feet, with Larrea, Carnegiea gigantea, or in yucca-grassland, locally plentiful in southeastern Arizona, south of the Gila River and eastward from the Papago Indian Reservation, east through southwestern New Mexico to the Rio Grande in Dona Ana County, south just into Sonora and Chihuahua.—Map No. 131.—(January) February to May.
Discussion:The var. australis achieves characteristic facies and climactic development only in the sahuaro deserts of southeastern Arizona, mostly below 3000 feet elevation, and is easily recognized there by its loosely racemose flowers of good size which are succeeded by pods of papery texture. It is ordinarily a coarse plant with diffuse, basally fistular stems and resembles var. yuccanus quite closely in technical characters, although distinguished at anthesis by its purple flowers mostly of slightly larger size and with keel-blades even longer and more prominent. However as var. yuccanus comes south toward the Gila River in central Arizona, the ordinarily yellowish or whitish petals assume a flush of pink or lilac toward the tips, and these populations serve as a connecting link between the two varieties. The typus of var. australis was chosen deliberately as an example of the most extreme phase of its category, with pods small, little inflated, and somewhat clawlike, superficially like those of a form of var. palans to which Jones 1930, p. 27) referred his own collection. It was realized from the first, but is perhaps worth emphasizing once again, that a pod of this nature is not a constant attribute of var. australis, even in Arizona. Quite often here, and always eastward so far as I am aware, the pod is greatly swollen, in no respect different from that of var. yuccanus or, except for its thinner texture, from that of var. diphysus. In southern New Mexico and Chihuahua the plants here referred to var. australis are for the most part more slender and have shorter racemes in fruit, thereby taking on such a close resemblance to var. diphysus that no doubt can exist of a near affinity in that direction also. As happens so often in A. lentiginosus, var. australis intergrades into a vicariant variety wherever the ranges of dispersal provide the proper setting.
Arizona United States of America North America
| New Mexico United States of America North America
| Sonora Mexico North America
| Chihuahua Mexico North America