Monographs Details: Astragalus ervoides var. maysillesii Barneby
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
Family:Fabaceae
Description:Latin Diagnosis - a var. ervoideo statura humiliori (caulibus saepissime 1—3 dm. tantum longis), pedunculis folio suffulcranti brevioribus, dentibus calycinis subulatis vel anguste lanceolatis elongatis (1.2-4.2 mm., nec 7-1.1 mm. longis), ovulisque magis numerosis (saepissime 14-20, nec 10-12) absimilis.

Variety Description - Thinly strigulose with hairs up to 0.2-0.45 mm. long, or glabrous below the thinly black- or fuscous-strigulose inflorescence; stipules 1-5 mm. long; leaflets (11) 13-25, narrowly oblanceolate, oblong-elliptic, or -obovate, more rarely linear- or lance-elliptic; racemes usually 20-40-, more rarely only 7-19-flowered; calyx 3.6-7.2 mm. long, the tube 2.1-3.2 mm., the teeth 1.2-4 (4.2) mm. long; petals white or pale cream-color, the keel-tip often faintly purplish, the banner sometimes lilac-tinged or -veined; banner 6.3—10.2 mm. long; wings (0.5 mm. shorter to 0.7 mm. longer than the banner) (6.6) 7-9.9 mm. long, the claws 2.6-4 mm., the blades (4.5) 4.8-7.3 mm. long, 1.4-2.7 (3) mm. wide; keel 5.6-7.6 mm. long, the claws 2.8-3.7 mm., the blades 3.2-4.2 mm. long, 1.9-2.4 (2.7) mm. wide.

Distribution and Ecology - Open rocky fields, meadow grasslands in oak brush, glades in xeric pine forest, more rarely in humid pine or oak woods, sometimes on limestone, 6700-9000 feet, apparently common in the Sierra Madre Occidental west of Durango, especially about the villages of Otinapa, El Salto, Coyotes Hacienda, and Llano Grande.—Map No. 51.—July to November.

Discussion:

The Maysilles milk-vetch occurs in two superficially disparate forms which I attempted, in the first instance, to separate in the following terms:

a. Racemes 20-40-flowered; flowers relatively large, the calyx 4.6-7.2 mm., its teeth 2.2-4.2 mm., the banner 8.6-10.2 mm., the keel 6.2-7.6 mm. long.

a. Racemes 7-19-flowered; flowers smaller, the calyx 3.6-4.5 mm., its teeth 1.2-1.7 mm., the banner 6.3-7.7 mm., the keel 5.6-6.2 mm. long.

The more slender, rarer, small-flowered phase (Maysilles 7015, 7313, 8128, all MICH) closely approaches var. ervoides in its comparatively few flowers of similar size, but differs in its short stems and consistently more numerous ovules. It serves as a connecting link between var. ervoides and the commoner, more robust state of var. Maysillesii, which might otherwise deserve specific status. That the plants of the two types from western Durango all represent one variable entity seems proven by comparison of Maysilles 8128 with the same collector’s Nos. 7121 and 7129, all taken, although in different seasons, from the same locality five miles north of Coyotes. The possible existence of two related forms living in close proximity, but separated by some unknown edaphic factor, seems unlikely but should perhaps be borne in mind.

Distribution:Durango Mexico North America|