7. Muhlenbergia mexicana (L.) Trin. (wirestem muhly)

Pl. 152 c, d; Map 617

Plants with well‑developed, scaly rhizomes, forming tufts. Flowering stems 30–95 cm long, erect or ascending, dull, minutely hairy between the nodes, especially below the nodes. Leaf sheaths glabrous or roughened, strongly keeled, the ligule 0.4–1.2 mm long. Leaf blades 5–30 cm long, 2–6 mm wide, flat, glabrous or less commonly somewhat roughened. Inflorescences dense, spikelike, terminal and lateral panicles 4–21 cm long, linear in outline, the base usually stalked and not enclosed by the subtending leaf sheath, the branches short, appressed to the main axis or nearly so. Spikelets 1.5–3.4 mm long (excluding the awns), short‑stalked, the stalks mostly shorter than the spikelets. Glumes about the same length, the body 1.5–3.4 mm long, about as long as the floret, lanceolate to narrowly triangular, only slightly overlapping at the base, the margins relatively straight and tapered gradually to the sharply pointed tip, strongly 1‑nerved, awnless or with an awn 0.2–1.5 mm long. Lemma with the body 1.3–3.4 mm long, lanceolate, the tip sharply pointed, awnless or less commonly with an awn 3–10 mm long, with a tuft of short hairs at the base, otherwise short‑hairy toward the base and roughened along the midnerve. Anthers 0.3–0.5(–0.7) mm long. Fruits 1.0–1.6 mm long. 2n=40. August–October.

Scattered nearly throughout the state, but absent from the Mississippi Lowlands Division and most of the Glaciated Plains (northern U.S. south to North Carolina, Texas, and California; Canada). Bottomland forests, mesic upland forests, ledges and bases of bluffs, banks of streams and rivers, and less commonly upland prairies, often on calcareous substrates; also pastures.

This species has proven to be somewhat more common and widespread in Missouri than was reported by Steyermark (1963). Plants with awned lemmas, which occur infrequently in eastern and southern Missouri, have been called f. ambigua (Torr.) Fernald.