Galactia regularis (L.) Britton, Stearns & Poggenb. (downy milk pea)

G. mississippiensis Vail

G. volubilis (L.) Britton, misapplied

G. volubilis var. mississippiensis (Vail) Rydb.

Dolichos regularis L.

Pl. 396 e, g; Map 1751

Plants perennial herbs, scrambling or climbing on other low vegetation, with a slender, branched caudex above a taproot. Stems 30–90 cm long, prostrate or trailing to loosely ascending, frequently twining, unarmed, sparsely to densely pubescent with short, fine, spreading to downward-curved hairs. Leaves alternate, pinnately trifoliate, the petiole 0.5–2.0 cm long, hairy. Stipules 1–3 mm long, narrowly lanceolate to lanceolate, mostly shed early; stipels minute (less than 0.3 mm long), linear, more or less persistent. Leaflets 1.5–4.0 cm long, 0.5–2.5 cm wide, elliptic to oblong or oblong-ovate, rounded to broadly angled at the base, bluntly pointed to rounded or occasionally slightly notched at the tip, the midvein extended as a minute sharp point at the very tip, the margins entire, the upper surface moderately hairy to glabrous or nearly so, the undersurface moderately to densely and finely hairy, pinnately veined, the undersurface lacking a noticeable network of veins or the fine network occasionally slightly evident. Terminal leaflet with the stalk 3–8 mm long, symmetric at the base; lateral leaflets essentially sessile above the pulvinus, mostly symmetric at the base. Inflorescences axillary, of clusters or racemes of 2–10 flowers, sometimes paired, the inflorescence stalk 0.5–3.0 cm long, hairy, the bracts 1.0–1.5 mm long, lanceolate, shed early; bractlets 0.6–1.0 mm long, ovate, loosely subtending the flowers, persistent. Cleistogamous flowers absent. Calyces 4–6 mm long, 5-lobed, but often appearing 4-lobed, because of fusion of the upper 2 lobes all or most of the way to the tip, the tube narrowly bell-shaped, hairy, the lobes about as long as to somewhat longer than the tube, the lowermost lobe longer than the others, ovate to triangular-lanceolate, angled or tapered to sharply pointed tips. Corollas papilionaceous, pink to pinkish purple (the banner, with a white or pale region toward the center, this often with an irregular, darker purple margin), fading to pale pink, the banner 6–9 mm long, 4–5 mm wide, the expanded portion broadly obovate, shallowly notched at the tip, often with a shallow longitudinal keel, bent backward, the wings 6–7 mm long, 1.5–2.0 mm wide, the expanded portion oblong, straight to somewhat incurved around the keel, the keel 6–8 mm long, 2–4 mm wide, straight to slightly curved upward, fused nearly to the usually bluntly pointed tip. Stamens 10, all of similar length, 9 of the filaments fused and 1 free, the fused portion 4–5 mm long, the free portion 1–2 mm long, the anthers small, attached near the midpoint. Ovary 3–4 mm long, finely hairy, the style 2–3 mm long, glabrous, the stigma minute, terminal. Fruits legumes, 2–5 cm long, 4–5 mm wide, narrowly oblong, straight, tapered at the tip to a short beak, flattened, herbaceous to somewhat papery, sparsely hairy at maturity, dehiscing by 2 valves, these green to tan at maturity, twisting spirally after dehiscence, with 3–8 seeds. Seeds 2.5–3.5 mm long, 1.5–2.5 mm wide, more or less kidney-shaped, flattened, the surface yellow to dark brown, sometimes mottled with purple, smooth, somewhat shiny. 2n=20. July–August.

Scattered in the Ozark, Ozark Border, and Mississippi Lowlands Divisions (eastern [mostly southeastern] U.S. west to Kansas and Texas). Glades, savannas, dry upland forests, tops of bluffs, and sand prairies.

This taxon is sometimes confused with several other species, in particular, G. volubilis (Gleason and Cronquist, 1991). These species are members of a variable complex of species that Isely (1990, 1998) referred to as the G. volubilis group. They vary in pubescence, length of the inflorescence, and flower size, but they appear to hybridize and are difficult to define and characterize. W. H. Duncan (1979) noted that the type specimen of G. regularis is identical to specimens that some authors had been calling G. volubilis or G. volubilis var. mississippiensis, and the name G. regularis is thus used here for the Missouri materials. True G. volubilis has longer racemes and larger flowers, and is mostly confined to the Atlantic and Gulf Coastal Plains from Virginia to Louisiana (W. H. Duncan, 1979).