Astragalus mollissimus var. Bigelovii

  • Title

    Astragalus mollissimus var. Bigelovii

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Astragalus mollissimus var. bigelovii (A.Gray) Barneby

  • Description

    233f.  Astragalus mollissimus var. Bigelovii

    Coarse and robust, nearly always shortly caulescent, the stems composed of up to 7 developed internodes and commonly 3-17 cm. long, sometimes essentially acaulescent, the herbage very densely, finely, and loosely villous-tomentose, the longer, spreading or ascending hairs up to (1.2) 1.5-2.7 mm. long, the vesture becoming rufous when dry; stipules large and conspicuous, 6—20 mm. long; leaves 9—26 cm. long, with (13) 19—27 ovate, obovate, oval, or broadly elliptic, obtuse or subacute leaflets 6—25 mm. long; peduncles (5) 8—22 cm. long; racemes oblong, rather densely (15) 20—45-flowered, the flowers subcontiguous or interrupted proximally, the axis (4) 5-11 cm. long in fruit; calyx 10.5-13.5 cm. long, the tube (8) 8.3-10.3 mm. long, (3.2) 4-5.2 mm. in diameter, the teeth (1.7) 2.6-4.4 mm. long; petals pink-purple; banner 17-22.5 mm. long, 9-11.5 mm. wide; wings 15—20.7 mm. long, the claws 7.4-10.6 mm., the blades 8.6-11.5 mm. long, 2.3-3.1 mm. wide; keel 13.4—18.6 mm. long, the claws 7.2—10.3 mm., the blades 6.6—9.3 mm. long, 2.7-3.8 mm. wide; pod ovoid-acuminate or lance-ellipsoid, gently incurved or nearly straight, 1—1.5 cm. long, (4) 4.5—8 mm. in diameter, sometimes a little turgid, the stiffly papery or leathery valves densely villous-tomentulose, the longest hairs up to 1—1.6 mm. long, the beak bilocular; ovules 20—31.—Collections: 52 (vi); representative: Jones 26,074 (CAS, POM); Pringle (from Santa Rita Mountains, Arizona) in 1884 (CAS, NY); McVaugh 8066 (SMU, TEX); Metcalfe 943 (CAS, NMC, US); Ripley & Barneby 11,166, 11,174 (CAS, RSA); Warnock 7680 (SRSC, TEX); Mex. Bound. Surv. (Parry) 256 (NY).

    Dry plains and foothills, in desert- or mesquite-grassland, sometimes among junipers, apparently most abundant on calcareous (caliche) soils but also in sandy loams of various origins and occasionally on basalt gravel, especially common on over-grazed and badly eroded cattle ranges, 4000-6000 (rarely up to 7500) feet, widespread and locally plentiful from extreme western Texas (Hudspeth County) west through southwestern New Mexico to southeastern Arizona (to Pima and Santa Cruz Counties), ascending the Rio Grande in New Mexico as far as Socorro and the San Augustine Plains in Catron County; to be expected in adjoining Mexico.—Map No. 99.—(January) March to June.

    Astragalus mollissimus var. Bigelovii (Gray) Barneby ap. B. L. Turner, Legum. Tex. 191. 1959, based on A. Bigelovii (John Milton Bigelow, 1804-1878, botanist with Lieut. Whipple’s Expedition of 1853-55) Gray, Pl. Wright. 2: 42. 1853.—"On the Organ Mountains northeast of El Paso; April 30; chiefly in fruit. (1358)."—Holotypus, (Wright 1358), collected April 30, 1852, GH! isotypi, K, NY, P, PH, SMU, US!—Tragacantha Bigelovii (Gray) O. Kze., Rev. Gen. 943. 1891 ("Bigelowii"). Astragalus Bigelovii var. typicus Barneby in Leafl. West. Bot. 4: 60. 1944.

    The varieties of the woolly locoweed described up to this point are closely interrelated and morphologically confluent where their ranges meet, forming a major division of the species. With var. Bigelovii we begin to consider a new set of varieties, quite similar to the foregoing in general aspect but differing in the inner structure of the pod, which is divided completely into two closed chambers by a septum produced into the apex of the short beak. In this group, which consists of vars. Bigelovii, marcidus, mogollonicus, and Matthewsii (the last transitional to a third group), the fruit dehisces apically as in var. mollissimus, but no aperture is provided for immediate dispersal of the seeds. These can only escape after the fallen pod has weathered on the ground or been broken open by animal agency.

    Bigelow’s woolly locoweed is the commonest member of its group; it is also the most leafy and coarsest in growth. In the yucca-grassland and mesquite-desert of southern New Mexico and adjoining Arizona and Texas, it plays the role of var. mollissimus on the prairies, becoming especially abundant on over-grazed and consequently eroded range. Equally poisonous when eaten fresh, as happens mostly in the early, arid spring months before the palatable grasses are vegetatively active, the mowed and dried plants are reportedly taken without ill effect. The leading features of var. Bigelovii are the exceptionally long, silvery but ultimately rusty, spirally twisted villi which clothe the stems and leaves, the comparatively large, purple flowers, and the densely villous-tomentulose pods which seem oddly small for the size of the plant. Known to be abundant in several places along the international boundary in New Mexico and Arizona, it must inevitably be collected in the future in northern Chihuahua and the northeast corner of Sonora; it is curious that there is no Mexican record for so conspicuous a plant.