10. Muhlenbergia sobolifera (Muhl.) Trin. (rock muhly)

Pl. 153 e, f; Map 620

Plants with well‑developed, scaly rhizomes, sometimes forming tufts. Flowering stems 35–100 cm long, erect or ascending, glabrous and shiny between the nodes or roughened just below the nodes. Leaf sheaths glabrous, rounded or slightly angled on the back, the ligule 0.3–0.8 mm long. Leaf blades 4–19 cm long, 2–8 mm wide, flat, glabrous or less commonly somewhat roughened. Inflorescences dense, spikelike, terminal and sometimes lateral panicles 4–19 cm long, linear in outline, sometimes somewhat arched, the base usually noticeably stalked and not enclosed by the subtending leaf sheath, the branches short, appressed to the main axis. Spikelets 1.7–2.7 mm long (excluding the awns), short‑stalked, the stalks mostly less than 2 times as long as the spikelets. Glumes about the same length, 1.0–2.3 mm long, 1/2–3/4 as long as the floret, lanceolate to narrowly triangular, strongly overlapping at the base, the margins curved from about the middle and tapered to the sharply pointed tip, 1(3)‑nerved, awnless or less commonly with an awn 0.1–0.4 mm long. Lemma with the body 1.7–2.7 mm long, lanceolate, the tip sharply pointed, awnless or with an awn 1–3 mm long, with a tuft of short hairs at the base, otherwise roughened along the midnerve. Anthers 0.4–0.9 mm long. Fruits 1.0–1.4 mm long. 2n=40, 42. July–October.

Scattered nearly throughout the state (northeastern U.S. and adjacent Canada west to Wisconsin, Nebraska, and Texas). Mesic to dry upland forests, ledges of bluffs, margins of glades, and less commonly banks of streams, on both calcareous and acidic substrates; also pastures, old fields, and roadsides.

This species usually has solitary stems (rarely clusters of few stems) and pale spikelets. Steyermark (1963) reported a single specimen from Christian County in which the lemmas had awns 1–3 mm long. This variant has been called f. setigera (Scribn.) Deam and occurs sporadically from Indiana to Missouri and south to Texas. Pohl (1969) recorded such plants mostly from Texas and noted that sometimes they also have roughened leaf blades. He indicated that these plants produce mostly misshapen and shrunken pollen grains and speculated that they might represent sterile hybrids between M. sobolifera and some other species of Muhlenbergia. This situation requires further study.