Astragalus missouriensis var. amphibolus
Astragalus missouriensis var. humistratus
Mancos milkvetch, Missouri milkvetch
archuleta milkvetch, Missouri milkvetch
to 10 cm.
10–15(–20) cm.
4–8-flowered.
9–12-flowered.
calyx 8.5–13 mm, tube 7–10 mm, lobes 1.5–3 mm;
corolla usually pink-purple, rarely white;
banner (14.5–)16–22(–24) mm;
keel (11.5–)12.8–17.3(–18.5) mm.
calyx 7.8–10 mm, tube 6–10 mm, lobes 1.5–3 mm;
corolla lavender, purple, or almost white, wing tips often white;
banner (17–)19–20.5 mm.
sometimes deciduous, ascending to descending, dorsiventrally compressed, lunately incurved, ellipsoid, (11–)15–25 × 7–9 mm, unilocular, apex obcompressed proximal to incurved beak, strigose.
ascending to descending, dorsiventrally compressed, lunately incurved, oblong-ellipsoid, (12–)17–20 × 6–9 mm, unilocular, apex obcompressed proximal to incurved beak, glabrous or sparsely strigulose.
35–55.
33–40.
Astragalus missouriensis var. amphibolus
Astragalus missouriensis var. humistratus
The fruits of var. amphibolus are initially dorsiventrally compressed, and ultimately dehisce apically while still attached to the inflorescence (though sometimes deciduous). The fruits have a lateral ridge down each valve, with the valves separated by more or less prominent bicarinate keels. In these features, along with the typically persistent fruits, the plants can be distinguished from the similar Astragalus amphioxys var. amphioxys where their ranges are contiguous, as in northwestern New Mexico and vicinity. R. C. Barneby (1947b, 1964) suggested that hybridization occurs between the two taxa.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Variety humistratus is locally distributed in Archuleta, Hinsdale, and La Plata counties, Colorado, and adjacent Rio Arriba County, New Mexico. It is anomalous in its strongly caulescent but mat-forming habit, and the slightly or plainly connate stipules. R. C. Barneby (1964) suggested a hybrid origin between Astragalus missouriensis and A. humistratus.
Variety humistratus is in the Center for Plant Conservation’s National Collection of Endangered Plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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