Astragalus missouriensis var. missouriensis
Astragalus missouriensis var. amphibolus
Missouri milk-vetch
Mancos milkvetch, Missouri milkvetch
to 15 cm.
to 10 cm.
(3–)5–15-flowered.
4–8-flowered.
calyx 9–12(–14.3) mm, tube 6.3–9(–9.3) mm, lobes 1.4–4.5(–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 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.
ascending, initially subterete or ± dorsiventrally compressed, ± straight, subsymmetrically oblong-ellipsoid, ± laterally compressed and obtuse-angled when mature, 15–28(–30) × (4–)5–9(–10) mm, subunilocular, base obtuse or sometimes cuneate, apex abruptly contracted into subulate, pungent beak, sutures prominent, strigulose.
sometimes deciduous, ascending to descending, dorsiventrally compressed, lunately incurved, ellipsoid, (11–)15–25 × 7–9 mm, unilocular, apex obcompressed proximal to incurved beak, strigose.
(33–)40–50(–56).
35–55.
= 22.
Astragalus missouriensis var. missouriensis
Astragalus missouriensis var. amphibolus
There is an irregular cline in flower size of var. missouriensis, from smallest in the north to largest in the south; caulescent forms appear to be more common southward (D. Isely 1998).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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