1. Juncus acuminatus Michx. (knotty-leaved rush, sharp-fruited rush)

Pl. 94 a–c; Map 358

Aerial stems 20–80 cm tall, caespitose, lacking noticeable rhizomes. Leaves with the auricles at the top of the sheaths 1.0–1.5 mm long, papery, rounded, the leaf blades 5–40 cm long, 1–3 mm wide, tubular and hollow, circular in cross-section, with cross-partitions at regular intervals. Basal leaves few, 1 or 2 of the sheaths lacking leaf blades. Leaves of the aerial stems 1 or 2. Inflorescences narrow panicles, the branches ascending or arching outward, the leaflike bract at the base shorter than the inflorescence. Flower clusters mostly 5–20 per inflorescence, mostly hemispherical, each with 10–50 flowers. Flowers lacking a pair of closely subtending bracts. Perianth 2.6–3.9 mm long, the sepals about as long as the petals, lanceolate, the tips acuminate. Stamens 3 per flower. Fruits 2.8–4.0 mm long, about as long as the perianth, narrowly ovate to elliptic in outline, the tip acute with a small mucro (hard tooth or point), 1-locular. Seeds 0.3–0.4 mm long, 1 end with a short, dark point. 2n=40. May–August.

Scattered throughout Missouri (eastern U.S. and adjacent Canada west to Texas, Mexico). Moist soil of fens, along spring branches and streams, and at the margins of ponds, lakes, and sloughs; also in mesic bottomland prairies and in wet depressions of upland prairies.