Astragalus humistratus var. sonorae (A.Gray) M.E.Jones
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
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Family
Fabaceae
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Scientific Name
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Type
"Mountain valleys, between the San Pedro and the Sonoita, Sonora, Sept. (1005)."—Holotypus (Wright 1005), collected in 1851, GH! isotypi, K, NY, PH, US!
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Synonyms
Astragalus sonorae A.Gray, Tragacantha sonorae (A.Gray) Kuntze, Batidophaca sonorae (A.Gray) Rydb., Batidophaca stipulacea Rydb.
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Description
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Variety Description - Closely resembling var. humistratus, but the herbage densely strigose-pilose and strigulose, cinereous or silvery, the longest, often rather loosely ascending hairs up to 1-1.5 mm. long; stems (5) 10-35 cm. long; stipules 3.5-10 mm. long; leaves (1.5) 2.5-5.5 cm. long, with (5) 9-17 leaflets 3-13 (15) mm. long; peduncles 3-8 cm. long; racemes 10-26-flowered, the axis 1.5-5.5 cm. long in fruit; calyx 4.6-6.8 (8) mm. long, the disc 0.6-1.1 mm. deep, the tube 2.5-3.5 mm. long, 2.5-3.1 (3.7) mm. in diameter, the teeth 2-4 (4.5) mm. long; petals dull purplish, amethyst-purple, or the banner alone purple-margined and -striate; banner 8.3-10.3 (11.4) long, 6-9 mm. wide; wings 8.4-10 (10.7) mm. long, the claws 2.4-3.4 mm., the blades 6-7.7 (8.2) mm. long, (1.8) 2.2-3.3 mm. wide; keel 7.3-8.8 (9.2) mm. long, the claws 2.4-3.5 mm., the blades 5.1-6 (6.5) mm. long, 2.4-3 mm. wide, abruptly incurved into a narrowly lance-triangular, porrect, beaklike apex; anthers 0.5-0.75 mm. long; pod lunately Unear-oblong or narrowly oblanceolate in profile, (1) 1.3-2 cm. long, 3.2-4.1 mm. in diameter, (3) 4-5 times longer than wide, triquetrously compressed and dorsally grooved in the lower three- fourths (rarely the lower half), passing distally into the laterally compressed, lance- acuminate beak, the valves densely strigulose; ovules (16) 18-26.
Distribution and Ecology - Dry gravelly and sandy hillsides, washes, and canyon floors, often among junipers but ascending into the lower edge of the yellow pine forest and coming out into yucca-grassland in the foothills, 4500-6600 feet, locally plentiful in southwestern New Mexico, southeastern Arizona, and northern Sonora, extending east across the Divide to the Rio Grande and Rio San Jose Valleys in westcentral and southcentral New Mexico.—Map No. 41A.—Late March to September, apparently most abundant in the spring months, but flowering a second time after summer rain.
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Discussion
The Sonoran ground-cover milk-vetch is essentially like var. humistratus in every way except for the more densely ashen or silky-pubescent foliage. It would surely rank as no more than a minor variant associated with relatively low elevations and a primarily vernal season of bloom, unless its range were perceptibly different. The type-collection of A. sonorae is unusual in the variety as described above because of its short pod, about 1 centimeter long and about 16-ovulate, although it is of the characteristic slender outline. No modern collections from Sonora have been examined, and some doubt remains as to whether Wright happened on a small-fruiting, perhaps depauperate colony or whether his plants represent a local minor variant intergradient to the next. The ground-cover milk-vetch of southeastern Arizona is unquestionably the same as that of southwestern New Mexico, which Rydberg described as B. stipulacea, and both are presumably of the same entity as that found across the border immediately to the south.
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Objects
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Distribution
Sonora Mexico North America| New Mexico United States of America North America| Arizona United States of America North America|